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llvm-mirror/lib/Target/ARM/ARMFrameLowering.cpp
Tim Northover a5f7171155 ARM: don't return by popping PC if we have to adjust the stack afterwards. 
In mandatory tail calling conventions we might have to deallocate stack
space used by our arguments before return. This happens after popping
CSRs, so the pop cannot be turned into the return itself in this case.

The else branch here was already a nop, so removing it as a tidy-up.
2021-07-21 09:35:14 +01:00

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//===- ARMFrameLowering.cpp - ARM Frame Information -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the ARM implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
//
// This file contains the ARM implementation of TargetFrameLowering class.
//
// On ARM, stack frames are structured as follows:
//
// The stack grows downward.
//
// All of the individual frame areas on the frame below are optional, i.e. it's
// possible to create a function so that the particular area isn't present
// in the frame.
//
// At function entry, the "frame" looks as follows:
//
// | | Higher address
// |-----------------------------------|
// | |
// | arguments passed on the stack |
// | |
// |-----------------------------------| <- sp
// | | Lower address
//
//
// After the prologue has run, the frame has the following general structure.
// Technically the last frame area (VLAs) doesn't get created until in the
// main function body, after the prologue is run. However, it's depicted here
// for completeness.
//
// | | Higher address
// |-----------------------------------|
// | |
// | arguments passed on the stack |
// | |
// |-----------------------------------| <- (sp at function entry)
// | |
// | varargs from registers |
// | |
// |-----------------------------------|
// | |
// | prev_fp, prev_lr |
// | (a.k.a. "frame record") |
// | |
// |- - - - - - - - - - - - - - - - - -| <- fp (r7 or r11)
// | |
// | callee-saved gpr registers |
// | |
// |-----------------------------------|
// | |
// | callee-saved fp/simd regs |
// | |
// |-----------------------------------|
// |.empty.space.to.make.part.below....|
// |.aligned.in.case.it.needs.more.than| (size of this area is unknown at
// |.the.standard.8-byte.alignment.....| compile time; if present)
// |-----------------------------------|
// | |
// | local variables of fixed size |
// | including spill slots |
// |-----------------------------------| <- base pointer (not defined by ABI,
// |.variable-sized.local.variables....| LLVM chooses r6)
// |.(VLAs)............................| (size of this area is unknown at
// |...................................| compile time)
// |-----------------------------------| <- sp
// | | Lower address
//
//
// To access the data in a frame, at-compile time, a constant offset must be
// computable from one of the pointers (fp, bp, sp) to access it. The size
// of the areas with a dotted background cannot be computed at compile-time
// if they are present, making it required to have all three of fp, bp and
// sp to be set up to be able to access all contents in the frame areas,
// assuming all of the frame areas are non-empty.
//
// For most functions, some of the frame areas are empty. For those functions,
// it may not be necessary to set up fp or bp:
// * A base pointer is definitely needed when there are both VLAs and local
// variables with more-than-default alignment requirements.
// * A frame pointer is definitely needed when there are local variables with
// more-than-default alignment requirements.
//
// In some cases when a base pointer is not strictly needed, it is generated
// anyway when offsets from the frame pointer to access local variables become
// so large that the offset can't be encoded in the immediate fields of loads
// or stores.
//
// The frame pointer might be chosen to be r7 or r11, depending on the target
// architecture and operating system. See ARMSubtarget::getFramePointerReg for
// details.
//
// Outgoing function arguments must be at the bottom of the stack frame when
// calling another function. If we do not have variable-sized stack objects, we
// can allocate a "reserved call frame" area at the bottom of the local
// variable area, large enough for all outgoing calls. If we do have VLAs, then
// the stack pointer must be decremented and incremented around each call to
// make space for the arguments below the VLAs.
//
//===----------------------------------------------------------------------===//
#include "ARMFrameLowering.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
#include "ARMConstantPoolValue.h"
#include "ARMMachineFunctionInfo.h"
#include "ARMSubtarget.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "MCTargetDesc/ARMBaseInfo.h"
#include "Utils/ARMBaseInfo.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <utility>
#include <vector>
#define DEBUG_TYPE "arm-frame-lowering"
using namespace llvm;
static cl::opt<bool>
SpillAlignedNEONRegs("align-neon-spills", cl::Hidden, cl::init(true),
cl::desc("Align ARM NEON spills in prolog and epilog"));
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs);
ARMFrameLowering::ARMFrameLowering(const ARMSubtarget &sti)
: TargetFrameLowering(StackGrowsDown, sti.getStackAlignment(), 0, Align(4)),
STI(sti) {}
bool ARMFrameLowering::keepFramePointer(const MachineFunction &MF) const {
// iOS always has a FP for backtracking, force other targets to keep their FP
// when doing FastISel. The emitted code is currently superior, and in cases
// like test-suite's lencod FastISel isn't quite correct when FP is eliminated.
return MF.getSubtarget<ARMSubtarget>().useFastISel();
}
/// Returns true if the target can safely skip saving callee-saved registers
/// for noreturn nounwind functions.
bool ARMFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const {
assert(MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
!MF.getFunction().hasFnAttribute(Attribute::UWTable));
// Frame pointer and link register are not treated as normal CSR, thus we
// can always skip CSR saves for nonreturning functions.
return true;
}
/// hasFP - Return true if the specified function should have a dedicated frame
/// pointer register. This is true if the function has variable sized allocas
/// or if frame pointer elimination is disabled.
bool ARMFrameLowering::hasFP(const MachineFunction &MF) const {
const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
const MachineFrameInfo &MFI = MF.getFrameInfo();
// ABI-required frame pointer.
if (MF.getTarget().Options.DisableFramePointerElim(MF))
return true;
// Frame pointer required for use within this function.
return (RegInfo->hasStackRealignment(MF) || MFI.hasVarSizedObjects() ||
MFI.isFrameAddressTaken());
}
/// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
/// not required, we reserve argument space for call sites in the function
/// immediately on entry to the current function. This eliminates the need for
/// add/sub sp brackets around call sites. Returns true if the call frame is
/// included as part of the stack frame.
bool ARMFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
unsigned CFSize = MFI.getMaxCallFrameSize();
// It's not always a good idea to include the call frame as part of the
// stack frame. ARM (especially Thumb) has small immediate offset to
// address the stack frame. So a large call frame can cause poor codegen
// and may even makes it impossible to scavenge a register.
if (CFSize >= ((1 << 12) - 1) / 2) // Half of imm12
return false;
return !MFI.hasVarSizedObjects();
}
/// canSimplifyCallFramePseudos - If there is a reserved call frame, the
/// call frame pseudos can be simplified. Unlike most targets, having a FP
/// is not sufficient here since we still may reference some objects via SP
/// even when FP is available in Thumb2 mode.
bool
ARMFrameLowering::canSimplifyCallFramePseudos(const MachineFunction &MF) const {
return hasReservedCallFrame(MF) || MF.getFrameInfo().hasVarSizedObjects();
}
// Returns how much of the incoming argument stack area we should clean up in an
// epilogue. For the C calling convention this will be 0, for guaranteed tail
// call conventions it can be positive (a normal return or a tail call to a
// function that uses less stack space for arguments) or negative (for a tail
// call to a function that needs more stack space than us for arguments).
static int getArgumentStackToRestore(MachineFunction &MF,
MachineBasicBlock &MBB) {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
bool IsTailCallReturn = false;
if (MBB.end() != MBBI) {
unsigned RetOpcode = MBBI->getOpcode();
IsTailCallReturn = RetOpcode == ARM::TCRETURNdi ||
RetOpcode == ARM::TCRETURNri;
}
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int ArgumentPopSize = 0;
if (IsTailCallReturn) {
MachineOperand &StackAdjust = MBBI->getOperand(1);
// For a tail-call in a callee-pops-arguments environment, some or all of
// the stack may actually be in use for the call's arguments, this is
// calculated during LowerCall and consumed here...
ArgumentPopSize = StackAdjust.getImm();
} else {
// ... otherwise the amount to pop is *all* of the argument space,
// conveniently stored in the MachineFunctionInfo by
// LowerFormalArguments. This will, of course, be zero for the C calling
// convention.
ArgumentPopSize = AFI->getArgumentStackToRestore();
}
return ArgumentPopSize;
}
static void emitRegPlusImmediate(
bool isARM, MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
const DebugLoc &dl, const ARMBaseInstrInfo &TII, unsigned DestReg,
unsigned SrcReg, int NumBytes, unsigned MIFlags = MachineInstr::NoFlags,
ARMCC::CondCodes Pred = ARMCC::AL, unsigned PredReg = 0) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes,
Pred, PredReg, TII, MIFlags);
else
emitT2RegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes,
Pred, PredReg, TII, MIFlags);
}
static void emitSPUpdate(bool isARM, MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI, const DebugLoc &dl,
const ARMBaseInstrInfo &TII, int NumBytes,
unsigned MIFlags = MachineInstr::NoFlags,
ARMCC::CondCodes Pred = ARMCC::AL,
unsigned PredReg = 0) {
emitRegPlusImmediate(isARM, MBB, MBBI, dl, TII, ARM::SP, ARM::SP, NumBytes,
MIFlags, Pred, PredReg);
}
static int sizeOfSPAdjustment(const MachineInstr &MI) {
int RegSize;
switch (MI.getOpcode()) {
case ARM::VSTMDDB_UPD:
RegSize = 8;
break;
case ARM::STMDB_UPD:
case ARM::t2STMDB_UPD:
RegSize = 4;
break;
case ARM::t2STR_PRE:
case ARM::STR_PRE_IMM:
return 4;
default:
llvm_unreachable("Unknown push or pop like instruction");
}
int count = 0;
// ARM and Thumb2 push/pop insts have explicit "sp, sp" operands (+
// pred) so the list starts at 4.
for (int i = MI.getNumOperands() - 1; i >= 4; --i)
count += RegSize;
return count;
}
static bool WindowsRequiresStackProbe(const MachineFunction &MF,
size_t StackSizeInBytes) {
const MachineFrameInfo &MFI = MF.getFrameInfo();
const Function &F = MF.getFunction();
unsigned StackProbeSize = (MFI.getStackProtectorIndex() > 0) ? 4080 : 4096;
if (F.hasFnAttribute("stack-probe-size"))
F.getFnAttribute("stack-probe-size")
.getValueAsString()
.getAsInteger(0, StackProbeSize);
return (StackSizeInBytes >= StackProbeSize) &&
!F.hasFnAttribute("no-stack-arg-probe");
}
namespace {
struct StackAdjustingInsts {
struct InstInfo {
MachineBasicBlock::iterator I;
unsigned SPAdjust;
bool BeforeFPSet;
};
SmallVector<InstInfo, 4> Insts;
void addInst(MachineBasicBlock::iterator I, unsigned SPAdjust,
bool BeforeFPSet = false) {
InstInfo Info = {I, SPAdjust, BeforeFPSet};
Insts.push_back(Info);
}
void addExtraBytes(const MachineBasicBlock::iterator I, unsigned ExtraBytes) {
auto Info =
llvm::find_if(Insts, [&](InstInfo &Info) { return Info.I == I; });
assert(Info != Insts.end() && "invalid sp adjusting instruction");
Info->SPAdjust += ExtraBytes;
}
void emitDefCFAOffsets(MachineBasicBlock &MBB, const DebugLoc &dl,
const ARMBaseInstrInfo &TII, bool HasFP) {
MachineFunction &MF = *MBB.getParent();
unsigned CFAOffset = 0;
for (auto &Info : Insts) {
if (HasFP && !Info.BeforeFPSet)
return;
CFAOffset += Info.SPAdjust;
unsigned CFIIndex = MF.addFrameInst(
MCCFIInstruction::cfiDefCfaOffset(nullptr, CFAOffset));
BuildMI(MBB, std::next(Info.I), dl,
TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
}
};
} // end anonymous namespace
/// Emit an instruction sequence that will align the address in
/// register Reg by zero-ing out the lower bits. For versions of the
/// architecture that support Neon, this must be done in a single
/// instruction, since skipAlignedDPRCS2Spills assumes it is done in a
/// single instruction. That function only gets called when optimizing
/// spilling of D registers on a core with the Neon instruction set
/// present.
static void emitAligningInstructions(MachineFunction &MF, ARMFunctionInfo *AFI,
const TargetInstrInfo &TII,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, const unsigned Reg,
const Align Alignment,
const bool MustBeSingleInstruction) {
const ARMSubtarget &AST =
static_cast<const ARMSubtarget &>(MF.getSubtarget());
const bool CanUseBFC = AST.hasV6T2Ops() || AST.hasV7Ops();
const unsigned AlignMask = Alignment.value() - 1U;
const unsigned NrBitsToZero = Log2(Alignment);
assert(!AFI->isThumb1OnlyFunction() && "Thumb1 not supported");
if (!AFI->isThumbFunction()) {
// if the BFC instruction is available, use that to zero the lower
// bits:
// bfc Reg, #0, log2(Alignment)
// otherwise use BIC, if the mask to zero the required number of bits
// can be encoded in the bic immediate field
// bic Reg, Reg, Alignment-1
// otherwise, emit
// lsr Reg, Reg, log2(Alignment)
// lsl Reg, Reg, log2(Alignment)
if (CanUseBFC) {
BuildMI(MBB, MBBI, DL, TII.get(ARM::BFC), Reg)
.addReg(Reg, RegState::Kill)
.addImm(~AlignMask)
.add(predOps(ARMCC::AL));
} else if (AlignMask <= 255) {
BuildMI(MBB, MBBI, DL, TII.get(ARM::BICri), Reg)
.addReg(Reg, RegState::Kill)
.addImm(AlignMask)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
} else {
assert(!MustBeSingleInstruction &&
"Shouldn't call emitAligningInstructions demanding a single "
"instruction to be emitted for large stack alignment for a target "
"without BFC.");
BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg)
.addReg(Reg, RegState::Kill)
.addImm(ARM_AM::getSORegOpc(ARM_AM::lsr, NrBitsToZero))
.add(predOps(ARMCC::AL))
.add(condCodeOp());
BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg)
.addReg(Reg, RegState::Kill)
.addImm(ARM_AM::getSORegOpc(ARM_AM::lsl, NrBitsToZero))
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
} else {
// Since this is only reached for Thumb-2 targets, the BFC instruction
// should always be available.
assert(CanUseBFC);
BuildMI(MBB, MBBI, DL, TII.get(ARM::t2BFC), Reg)
.addReg(Reg, RegState::Kill)
.addImm(~AlignMask)
.add(predOps(ARMCC::AL));
}
}
/// We need the offset of the frame pointer relative to other MachineFrameInfo
/// offsets which are encoded relative to SP at function begin.
/// See also emitPrologue() for how the FP is set up.
/// Unfortunately we cannot determine this value in determineCalleeSaves() yet
/// as assignCalleeSavedSpillSlots() hasn't run at this point. Instead we use
/// this to produce a conservative estimate that we check in an assert() later.
static int getMaxFPOffset(const ARMSubtarget &STI, const ARMFunctionInfo &AFI) {
// For Thumb1, push.w isn't available, so the first push will always push
// r7 and lr onto the stack first.
if (AFI.isThumb1OnlyFunction())
return -AFI.getArgRegsSaveSize() - (2 * 4);
// This is a conservative estimation: Assume the frame pointer being r7 and
// pc("r15") up to r8 getting spilled before (= 8 registers).
int FPCXTSaveSize = (STI.hasV8_1MMainlineOps() && AFI.isCmseNSEntryFunction()) ? 4 : 0;
return - FPCXTSaveSize - AFI.getArgRegsSaveSize() - (8 * 4);
}
void ARMFrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo &MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
MachineModuleInfo &MMI = MF.getMMI();
MCContext &Context = MMI.getContext();
const TargetMachine &TM = MF.getTarget();
const MCRegisterInfo *MRI = Context.getRegisterInfo();
const ARMBaseRegisterInfo *RegInfo = STI.getRegisterInfo();
const ARMBaseInstrInfo &TII = *STI.getInstrInfo();
assert(!AFI->isThumb1OnlyFunction() &&
"This emitPrologue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
Align Alignment = STI.getFrameLowering()->getStackAlign();
unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize();
unsigned NumBytes = MFI.getStackSize();
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
int FPCXTSaveSize = 0;
// Debug location must be unknown since the first debug location is used
// to determine the end of the prologue.
DebugLoc dl;
Register FramePtr = RegInfo->getFrameRegister(MF);
// Determine the sizes of each callee-save spill areas and record which frame
// belongs to which callee-save spill areas.
unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
int FramePtrSpillFI = 0;
int D8SpillFI = 0;
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction().getCallingConv() == CallingConv::GHC)
return;
StackAdjustingInsts DefCFAOffsetCandidates;
bool HasFP = hasFP(MF);
// Allocate the vararg register save area.
if (ArgRegsSaveSize) {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -ArgRegsSaveSize,
MachineInstr::FrameSetup);
DefCFAOffsetCandidates.addInst(std::prev(MBBI), ArgRegsSaveSize, true);
}
if (!AFI->hasStackFrame() &&
(!STI.isTargetWindows() || !WindowsRequiresStackProbe(MF, NumBytes))) {
if (NumBytes - ArgRegsSaveSize != 0) {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -(NumBytes - ArgRegsSaveSize),
MachineInstr::FrameSetup);
DefCFAOffsetCandidates.addInst(std::prev(MBBI),
NumBytes - ArgRegsSaveSize, true);
}
DefCFAOffsetCandidates.emitDefCFAOffsets(MBB, dl, TII, HasFP);
return;
}
// Determine spill area sizes.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
int FI = CSI[i].getFrameIdx();
switch (Reg) {
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
case ARM::R12:
if (STI.splitFramePushPop(MF)) {
GPRCS2Size += 4;
break;
}
LLVM_FALLTHROUGH;
case ARM::R0:
case ARM::R1:
case ARM::R2:
case ARM::R3:
case ARM::R4:
case ARM::R5:
case ARM::R6:
case ARM::R7:
case ARM::LR:
if (Reg == FramePtr)
FramePtrSpillFI = FI;
GPRCS1Size += 4;
break;
case ARM::FPCXTNS:
FPCXTSaveSize = 4;
break;
default:
// This is a DPR. Exclude the aligned DPRCS2 spills.
if (Reg == ARM::D8)
D8SpillFI = FI;
if (Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs())
DPRCSSize += 8;
}
}
// Move past FPCXT area.
MachineBasicBlock::iterator LastPush = MBB.end(), GPRCS1Push, GPRCS2Push;
if (FPCXTSaveSize > 0) {
LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, FPCXTSaveSize, true);
}
// Move past area 1.
if (GPRCS1Size > 0) {
GPRCS1Push = LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, GPRCS1Size, true);
}
// Determine starting offsets of spill areas.
unsigned FPCXTOffset = NumBytes - ArgRegsSaveSize - FPCXTSaveSize;
unsigned GPRCS1Offset = FPCXTOffset - GPRCS1Size;
unsigned GPRCS2Offset = GPRCS1Offset - GPRCS2Size;
Align DPRAlign = DPRCSSize ? std::min(Align(8), Alignment) : Align(4);
unsigned DPRGapSize =
(GPRCS1Size + GPRCS2Size + FPCXTSaveSize + ArgRegsSaveSize) %
DPRAlign.value();
unsigned DPRCSOffset = GPRCS2Offset - DPRGapSize - DPRCSSize;
int FramePtrOffsetInPush = 0;
if (HasFP) {
int FPOffset = MFI.getObjectOffset(FramePtrSpillFI);
assert(getMaxFPOffset(STI, *AFI) <= FPOffset &&
"Max FP estimation is wrong");
FramePtrOffsetInPush = FPOffset + ArgRegsSaveSize + FPCXTSaveSize;
AFI->setFramePtrSpillOffset(MFI.getObjectOffset(FramePtrSpillFI) +
NumBytes);
}
AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
// Move past area 2.
if (GPRCS2Size > 0) {
GPRCS2Push = LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, GPRCS2Size);
}
// Prolog/epilog inserter assumes we correctly align DPRs on the stack, so our
// .cfi_offset operations will reflect that.
if (DPRGapSize) {
assert(DPRGapSize == 4 && "unexpected alignment requirements for DPRs");
if (LastPush != MBB.end() &&
tryFoldSPUpdateIntoPushPop(STI, MF, &*LastPush, DPRGapSize))
DefCFAOffsetCandidates.addExtraBytes(LastPush, DPRGapSize);
else {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -DPRGapSize,
MachineInstr::FrameSetup);
DefCFAOffsetCandidates.addInst(std::prev(MBBI), DPRGapSize);
}
}
// Move past area 3.
if (DPRCSSize > 0) {
// Since vpush register list cannot have gaps, there may be multiple vpush
// instructions in the prologue.
while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::VSTMDDB_UPD) {
DefCFAOffsetCandidates.addInst(MBBI, sizeOfSPAdjustment(*MBBI));
LastPush = MBBI++;
}
}
// Move past the aligned DPRCS2 area.
if (AFI->getNumAlignedDPRCS2Regs() > 0) {
MBBI = skipAlignedDPRCS2Spills(MBBI, AFI->getNumAlignedDPRCS2Regs());
// The code inserted by emitAlignedDPRCS2Spills realigns the stack, and
// leaves the stack pointer pointing to the DPRCS2 area.
//
// Adjust NumBytes to represent the stack slots below the DPRCS2 area.
NumBytes += MFI.getObjectOffset(D8SpillFI);
} else
NumBytes = DPRCSOffset;
if (STI.isTargetWindows() && WindowsRequiresStackProbe(MF, NumBytes)) {
uint32_t NumWords = NumBytes >> 2;
if (NumWords < 65536)
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), ARM::R4)
.addImm(NumWords)
.setMIFlags(MachineInstr::FrameSetup)
.add(predOps(ARMCC::AL));
else
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R4)
.addImm(NumWords)
.setMIFlags(MachineInstr::FrameSetup);
switch (TM.getCodeModel()) {
case CodeModel::Tiny:
llvm_unreachable("Tiny code model not available on ARM.");
case CodeModel::Small:
case CodeModel::Medium:
case CodeModel::Kernel:
BuildMI(MBB, MBBI, dl, TII.get(ARM::tBL))
.add(predOps(ARMCC::AL))
.addExternalSymbol("__chkstk")
.addReg(ARM::R4, RegState::Implicit)
.setMIFlags(MachineInstr::FrameSetup);
break;
case CodeModel::Large:
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R12)
.addExternalSymbol("__chkstk")
.setMIFlags(MachineInstr::FrameSetup);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tBLXr))
.add(predOps(ARMCC::AL))
.addReg(ARM::R12, RegState::Kill)
.addReg(ARM::R4, RegState::Implicit)
.setMIFlags(MachineInstr::FrameSetup);
break;
}
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr), ARM::SP)
.addReg(ARM::SP, RegState::Kill)
.addReg(ARM::R4, RegState::Kill)
.setMIFlags(MachineInstr::FrameSetup)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
NumBytes = 0;
}
if (NumBytes) {
// Adjust SP after all the callee-save spills.
if (AFI->getNumAlignedDPRCS2Regs() == 0 &&
tryFoldSPUpdateIntoPushPop(STI, MF, &*LastPush, NumBytes))
DefCFAOffsetCandidates.addExtraBytes(LastPush, NumBytes);
else {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
DefCFAOffsetCandidates.addInst(std::prev(MBBI), NumBytes);
}
if (HasFP && isARM)
// Restore from fp only in ARM mode: e.g. sub sp, r7, #24
// Note it's not safe to do this in Thumb2 mode because it would have
// taken two instructions:
// mov sp, r7
// sub sp, #24
// If an interrupt is taken between the two instructions, then sp is in
// an inconsistent state (pointing to the middle of callee-saved area).
// The interrupt handler can end up clobbering the registers.
AFI->setShouldRestoreSPFromFP(true);
}
// Set FP to point to the stack slot that contains the previous FP.
// For iOS, FP is R7, which has now been stored in spill area 1.
// Otherwise, if this is not iOS, all the callee-saved registers go
// into spill area 1, including the FP in R11. In either case, it
// is in area one and the adjustment needs to take place just after
// that push.
if (HasFP) {
MachineBasicBlock::iterator AfterPush = std::next(GPRCS1Push);
unsigned PushSize = sizeOfSPAdjustment(*GPRCS1Push);
emitRegPlusImmediate(!AFI->isThumbFunction(), MBB, AfterPush,
dl, TII, FramePtr, ARM::SP,
PushSize + FramePtrOffsetInPush,
MachineInstr::FrameSetup);
if (FramePtrOffsetInPush + PushSize != 0) {
unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfa(
nullptr, MRI->getDwarfRegNum(FramePtr, true),
FPCXTSaveSize + ArgRegsSaveSize - FramePtrOffsetInPush));
BuildMI(MBB, AfterPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
} else {
unsigned CFIIndex =
MF.addFrameInst(MCCFIInstruction::createDefCfaRegister(
nullptr, MRI->getDwarfRegNum(FramePtr, true)));
BuildMI(MBB, AfterPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
}
// Now that the prologue's actual instructions are finalised, we can insert
// the necessary DWARF cf instructions to describe the situation. Start by
// recording where each register ended up:
if (GPRCS1Size > 0) {
MachineBasicBlock::iterator Pos = std::next(GPRCS1Push);
int CFIIndex;
for (const auto &Entry : CSI) {
unsigned Reg = Entry.getReg();
int FI = Entry.getFrameIdx();
switch (Reg) {
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
case ARM::R12:
if (STI.splitFramePushPop(MF))
break;
LLVM_FALLTHROUGH;
case ARM::R0:
case ARM::R1:
case ARM::R2:
case ARM::R3:
case ARM::R4:
case ARM::R5:
case ARM::R6:
case ARM::R7:
case ARM::LR:
CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(Reg, true), MFI.getObjectOffset(FI)));
BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
break;
}
}
}
if (GPRCS2Size > 0) {
MachineBasicBlock::iterator Pos = std::next(GPRCS2Push);
for (const auto &Entry : CSI) {
unsigned Reg = Entry.getReg();
int FI = Entry.getFrameIdx();
switch (Reg) {
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
case ARM::R12:
if (STI.splitFramePushPop(MF)) {
unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
unsigned Offset = MFI.getObjectOffset(FI);
unsigned CFIIndex = MF.addFrameInst(
MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
break;
}
}
}
if (DPRCSSize > 0) {
// Since vpush register list cannot have gaps, there may be multiple vpush
// instructions in the prologue.
MachineBasicBlock::iterator Pos = std::next(LastPush);
for (const auto &Entry : CSI) {
unsigned Reg = Entry.getReg();
int FI = Entry.getFrameIdx();
if ((Reg >= ARM::D0 && Reg <= ARM::D31) &&
(Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs())) {
unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
unsigned Offset = MFI.getObjectOffset(FI);
unsigned CFIIndex = MF.addFrameInst(
MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex)
.setMIFlags(MachineInstr::FrameSetup);
}
}
}
// Now we can emit descriptions of where the canonical frame address was
// throughout the process. If we have a frame pointer, it takes over the job
// half-way through, so only the first few .cfi_def_cfa_offset instructions
// actually get emitted.
DefCFAOffsetCandidates.emitDefCFAOffsets(MBB, dl, TII, HasFP);
if (STI.isTargetELF() && hasFP(MF))
MFI.setOffsetAdjustment(MFI.getOffsetAdjustment() -
AFI->getFramePtrSpillOffset());
AFI->setFPCXTSaveAreaSize(FPCXTSaveSize);
AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
AFI->setDPRCalleeSavedGapSize(DPRGapSize);
AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
// If we need dynamic stack realignment, do it here. Be paranoid and make
// sure if we also have VLAs, we have a base pointer for frame access.
// If aligned NEON registers were spilled, the stack has already been
// realigned.
if (!AFI->getNumAlignedDPRCS2Regs() && RegInfo->hasStackRealignment(MF)) {
Align MaxAlign = MFI.getMaxAlign();
assert(!AFI->isThumb1OnlyFunction());
if (!AFI->isThumbFunction()) {
emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::SP, MaxAlign,
false);
} else {
// We cannot use sp as source/dest register here, thus we're using r4 to
// perform the calculations. We're emitting the following sequence:
// mov r4, sp
// -- use emitAligningInstructions to produce best sequence to zero
// -- out lower bits in r4
// mov sp, r4
// FIXME: It will be better just to find spare register here.
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4)
.addReg(ARM::SP, RegState::Kill)
.add(predOps(ARMCC::AL));
emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::R4, MaxAlign,
false);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(ARM::R4, RegState::Kill)
.add(predOps(ARMCC::AL));
}
AFI->setShouldRestoreSPFromFP(true);
}
// If we need a base pointer, set it up here. It's whatever the value
// of the stack pointer is at this point. Any variable size objects
// will be allocated after this, so we can still use the base pointer
// to reference locals.
// FIXME: Clarify FrameSetup flags here.
if (RegInfo->hasBasePointer(MF)) {
if (isARM)
BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), RegInfo->getBaseRegister())
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
else
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), RegInfo->getBaseRegister())
.addReg(ARM::SP)
.add(predOps(ARMCC::AL));
}
// If the frame has variable sized objects then the epilogue must restore
// the sp from fp. We can assume there's an FP here since hasFP already
// checks for hasVarSizedObjects.
if (MFI.hasVarSizedObjects())
AFI->setShouldRestoreSPFromFP(true);
}
void ARMFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineFrameInfo &MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
assert(!AFI->isThumb1OnlyFunction() &&
"This emitEpilogue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
// Amount of stack space we reserved next to incoming args for either
// varargs registers or stack arguments in tail calls made by this function.
unsigned ReservedArgStack = AFI->getArgRegsSaveSize();
// How much of the stack used by incoming arguments this function is expected
// to restore in this particular epilogue.
int IncomingArgStackToRestore = getArgumentStackToRestore(MF, MBB);
int NumBytes = (int)MFI.getStackSize();
Register FramePtr = RegInfo->getFrameRegister(MF);
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction().getCallingConv() == CallingConv::GHC)
return;
// First put ourselves on the first (from top) terminator instructions.
MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
if (!AFI->hasStackFrame()) {
if (NumBytes - ReservedArgStack != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes - ReservedArgStack,
MachineInstr::FrameDestroy);
} else {
// Unwind MBBI to point to first LDR / VLDRD.
if (MBBI != MBB.begin()) {
do {
--MBBI;
} while (MBBI != MBB.begin() &&
MBBI->getFlag(MachineInstr::FrameDestroy));
if (!MBBI->getFlag(MachineInstr::FrameDestroy))
++MBBI;
}
// Move SP to start of FP callee save spill area.
NumBytes -= (ReservedArgStack +
AFI->getFPCXTSaveAreaSize() +
AFI->getGPRCalleeSavedArea1Size() +
AFI->getGPRCalleeSavedArea2Size() +
AFI->getDPRCalleeSavedGapSize() +
AFI->getDPRCalleeSavedAreaSize());
// Reset SP based on frame pointer only if the stack frame extends beyond
// frame pointer stack slot or target is ELF and the function has FP.
if (AFI->shouldRestoreSPFromFP()) {
NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
if (NumBytes) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, FramePtr, -NumBytes,
ARMCC::AL, 0, TII,
MachineInstr::FrameDestroy);
else {
// It's not possible to restore SP from FP in a single instruction.
// For iOS, this looks like:
// mov sp, r7
// sub sp, #24
// This is bad, if an interrupt is taken after the mov, sp is in an
// inconsistent state.
// Use the first callee-saved register as a scratch register.
assert(!MFI.getPristineRegs(MF).test(ARM::R4) &&
"No scratch register to restore SP from FP!");
emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
ARMCC::AL, 0, TII, MachineInstr::FrameDestroy);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(ARM::R4)
.add(predOps(ARMCC::AL))
.setMIFlag(MachineInstr::FrameDestroy);
}
} else {
// Thumb2 or ARM.
if (isARM)
BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), ARM::SP)
.addReg(FramePtr)
.add(predOps(ARMCC::AL))
.add(condCodeOp())
.setMIFlag(MachineInstr::FrameDestroy);
else
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(FramePtr)
.add(predOps(ARMCC::AL))
.setMIFlag(MachineInstr::FrameDestroy);
}
} else if (NumBytes &&
!tryFoldSPUpdateIntoPushPop(STI, MF, &*MBBI, NumBytes))
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes,
MachineInstr::FrameDestroy);
// Increment past our save areas.
if (MBBI != MBB.end() && AFI->getDPRCalleeSavedAreaSize()) {
MBBI++;
// Since vpop register list cannot have gaps, there may be multiple vpop
// instructions in the epilogue.
while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::VLDMDIA_UPD)
MBBI++;
}
if (AFI->getDPRCalleeSavedGapSize()) {
assert(AFI->getDPRCalleeSavedGapSize() == 4 &&
"unexpected DPR alignment gap");
emitSPUpdate(isARM, MBB, MBBI, dl, TII, AFI->getDPRCalleeSavedGapSize(),
MachineInstr::FrameDestroy);
}
if (AFI->getGPRCalleeSavedArea2Size()) MBBI++;
if (AFI->getGPRCalleeSavedArea1Size()) MBBI++;
if (AFI->getFPCXTSaveAreaSize()) MBBI++;
}
if (ReservedArgStack || IncomingArgStackToRestore) {
assert((int)ReservedArgStack + IncomingArgStackToRestore >= 0 &&
"attempting to restore negative stack amount");
emitSPUpdate(isARM, MBB, MBBI, dl, TII,
ReservedArgStack + IncomingArgStackToRestore,
MachineInstr::FrameDestroy);
}
}
/// getFrameIndexReference - Provide a base+offset reference to an FI slot for
/// debug info. It's the same as what we use for resolving the code-gen
/// references for now. FIXME: This can go wrong when references are
/// SP-relative and simple call frames aren't used.
StackOffset ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF,
int FI,
Register &FrameReg) const {
return StackOffset::getFixed(ResolveFrameIndexReference(MF, FI, FrameReg, 0));
}
int ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
int FI, Register &FrameReg,
int SPAdj) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int Offset = MFI.getObjectOffset(FI) + MFI.getStackSize();
int FPOffset = Offset - AFI->getFramePtrSpillOffset();
bool isFixed = MFI.isFixedObjectIndex(FI);
FrameReg = ARM::SP;
Offset += SPAdj;
// SP can move around if there are allocas. We may also lose track of SP
// when emergency spilling inside a non-reserved call frame setup.
bool hasMovingSP = !hasReservedCallFrame(MF);
// When dynamically realigning the stack, use the frame pointer for
// parameters, and the stack/base pointer for locals.
if (RegInfo->hasStackRealignment(MF)) {
assert(hasFP(MF) && "dynamic stack realignment without a FP!");
if (isFixed) {
FrameReg = RegInfo->getFrameRegister(MF);
Offset = FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) &&
"VLAs and dynamic stack alignment, but missing base pointer!");
FrameReg = RegInfo->getBaseRegister();
Offset -= SPAdj;
}
return Offset;
}
// If there is a frame pointer, use it when we can.
if (hasFP(MF) && AFI->hasStackFrame()) {
// Use frame pointer to reference fixed objects. Use it for locals if
// there are VLAs (and thus the SP isn't reliable as a base).
if (isFixed || (hasMovingSP && !RegInfo->hasBasePointer(MF))) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) && "missing base pointer!");
if (AFI->isThumb2Function()) {
// Try to use the frame pointer if we can, else use the base pointer
// since it's available. This is handy for the emergency spill slot, in
// particular.
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
} else if (AFI->isThumbFunction()) {
// Prefer SP to base pointer, if the offset is suitably aligned and in
// range as the effective range of the immediate offset is bigger when
// basing off SP.
// Use add <rd>, sp, #<imm8>
// ldr <rd>, [sp, #<imm8>]
if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020)
return Offset;
// In Thumb2 mode, the negative offset is very limited. Try to avoid
// out of range references. ldr <rt>,[<rn>, #-<imm8>]
if (AFI->isThumb2Function() && FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
} else if (Offset > (FPOffset < 0 ? -FPOffset : FPOffset)) {
// Otherwise, use SP or FP, whichever is closer to the stack slot.
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
// Use the base pointer if we have one.
// FIXME: Maybe prefer sp on Thumb1 if it's legal and the offset is cheaper?
// That can happen if we forced a base pointer for a large call frame.
if (RegInfo->hasBasePointer(MF)) {
FrameReg = RegInfo->getBaseRegister();
Offset -= SPAdj;
}
return Offset;
}
void ARMFrameLowering::emitPushInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
ArrayRef<CalleeSavedInfo> CSI,
unsigned StmOpc, unsigned StrOpc,
bool NoGap, bool (*Func)(unsigned, bool),
unsigned NumAlignedDPRCS2Regs,
unsigned MIFlags) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
DebugLoc DL;
using RegAndKill = std::pair<unsigned, bool>;
SmallVector<RegAndKill, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
for (; i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (!(Func)(Reg, STI.splitFramePushPop(MF))) continue;
// D-registers in the aligned area DPRCS2 are NOT spilled here.
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
continue;
const MachineRegisterInfo &MRI = MF.getRegInfo();
bool isLiveIn = MRI.isLiveIn(Reg);
if (!isLiveIn && !MRI.isReserved(Reg))
MBB.addLiveIn(Reg);
// If NoGap is true, push consecutive registers and then leave the rest
// for other instructions. e.g.
// vpush {d8, d10, d11} -> vpush {d8}, vpush {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
// Do not set a kill flag on values that are also marked as live-in. This
// happens with the @llvm-returnaddress intrinsic and with arguments
// passed in callee saved registers.
// Omitting the kill flags is conservatively correct even if the live-in
// is not used after all.
Regs.push_back(std::make_pair(Reg, /*isKill=*/!isLiveIn));
}
if (Regs.empty())
continue;
llvm::sort(Regs, [&](const RegAndKill &LHS, const RegAndKill &RHS) {
return TRI.getEncodingValue(LHS.first) < TRI.getEncodingValue(RHS.first);
});
if (Regs.size() > 1 || StrOpc== 0) {
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(StmOpc), ARM::SP)
.addReg(ARM::SP)
.setMIFlags(MIFlags)
.add(predOps(ARMCC::AL));
for (unsigned i = 0, e = Regs.size(); i < e; ++i)
MIB.addReg(Regs[i].first, getKillRegState(Regs[i].second));
} else if (Regs.size() == 1) {
BuildMI(MBB, MI, DL, TII.get(StrOpc), ARM::SP)
.addReg(Regs[0].first, getKillRegState(Regs[0].second))
.addReg(ARM::SP)
.setMIFlags(MIFlags)
.addImm(-4)
.add(predOps(ARMCC::AL));
}
Regs.clear();
// Put any subsequent vpush instructions before this one: they will refer to
// higher register numbers so need to be pushed first in order to preserve
// monotonicity.
if (MI != MBB.begin())
--MI;
}
}
void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
MutableArrayRef<CalleeSavedInfo> CSI,
unsigned LdmOpc, unsigned LdrOpc,
bool isVarArg, bool NoGap,
bool (*Func)(unsigned, bool),
unsigned NumAlignedDPRCS2Regs) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL;
bool isTailCall = false;
bool isInterrupt = false;
bool isTrap = false;
bool isCmseEntry = false;
if (MBB.end() != MI) {
DL = MI->getDebugLoc();
unsigned RetOpcode = MI->getOpcode();
isTailCall = (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNri);
isInterrupt =
RetOpcode == ARM::SUBS_PC_LR || RetOpcode == ARM::t2SUBS_PC_LR;
isTrap =
RetOpcode == ARM::TRAP || RetOpcode == ARM::TRAPNaCl ||
RetOpcode == ARM::tTRAP;
isCmseEntry = (RetOpcode == ARM::tBXNS || RetOpcode == ARM::tBXNS_RET);
}
SmallVector<unsigned, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
bool DeleteRet = false;
for (; i != 0; --i) {
CalleeSavedInfo &Info = CSI[i-1];
unsigned Reg = Info.getReg();
if (!(Func)(Reg, STI.splitFramePushPop(MF))) continue;
// The aligned reloads from area DPRCS2 are not inserted here.
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
continue;
if (Reg == ARM::LR && !isTailCall && !isVarArg && !isInterrupt &&
!isCmseEntry && !isTrap && AFI->getArgumentStackToRestore() == 0 &&
STI.hasV5TOps() && MBB.succ_empty()) {
Reg = ARM::PC;
// Fold the return instruction into the LDM.
DeleteRet = true;
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
// We 'restore' LR into PC so it is not live out of the return block:
// Clear Restored bit.
Info.setRestored(false);
}
// If NoGap is true, pop consecutive registers and then leave the rest
// for other instructions. e.g.
// vpop {d8, d10, d11} -> vpop {d8}, vpop {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
Regs.push_back(Reg);
}
if (Regs.empty())
continue;
llvm::sort(Regs, [&](unsigned LHS, unsigned RHS) {
return TRI.getEncodingValue(LHS) < TRI.getEncodingValue(RHS);
});
if (Regs.size() > 1 || LdrOpc == 0) {
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(LdmOpc), ARM::SP)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameDestroy);
for (unsigned i = 0, e = Regs.size(); i < e; ++i)
MIB.addReg(Regs[i], getDefRegState(true));
if (DeleteRet) {
if (MI != MBB.end()) {
MIB.copyImplicitOps(*MI);
MI->eraseFromParent();
}
}
MI = MIB;
} else if (Regs.size() == 1) {
// If we adjusted the reg to PC from LR above, switch it back here. We
// only do that for LDM.
if (Regs[0] == ARM::PC)
Regs[0] = ARM::LR;
MachineInstrBuilder MIB =
BuildMI(MBB, MI, DL, TII.get(LdrOpc), Regs[0])
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.setMIFlags(MachineInstr::FrameDestroy);
// ARM mode needs an extra reg0 here due to addrmode2. Will go away once
// that refactoring is complete (eventually).
if (LdrOpc == ARM::LDR_POST_REG || LdrOpc == ARM::LDR_POST_IMM) {
MIB.addReg(0);
MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::add, 4, ARM_AM::no_shift));
} else
MIB.addImm(4);
MIB.add(predOps(ARMCC::AL));
}
Regs.clear();
// Put any subsequent vpop instructions after this one: they will refer to
// higher register numbers so need to be popped afterwards.
if (MI != MBB.end())
++MI;
}
}
/// Emit aligned spill instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. Also insert stack realignment code and leave the stack
/// pointer pointing to the d8 spill slot.
static void emitAlignedDPRCS2Spills(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
ArrayRef<CalleeSavedInfo> CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
MachineFrameInfo &MFI = MF.getFrameInfo();
// Mark the D-register spill slots as properly aligned. Since MFI computes
// stack slot layout backwards, this can actually mean that the d-reg stack
// slot offsets can be wrong. The offset for d8 will always be correct.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned DNum = CSI[i].getReg() - ARM::D8;
if (DNum > NumAlignedDPRCS2Regs - 1)
continue;
int FI = CSI[i].getFrameIdx();
// The even-numbered registers will be 16-byte aligned, the odd-numbered
// registers will be 8-byte aligned.
MFI.setObjectAlignment(FI, DNum % 2 ? Align(8) : Align(16));
// The stack slot for D8 needs to be maximally aligned because this is
// actually the point where we align the stack pointer. MachineFrameInfo
// computes all offsets relative to the incoming stack pointer which is a
// bit weird when realigning the stack. Any extra padding for this
// over-alignment is not realized because the code inserted below adjusts
// the stack pointer by numregs * 8 before aligning the stack pointer.
if (DNum == 0)
MFI.setObjectAlignment(FI, MFI.getMaxAlign());
}
// Move the stack pointer to the d8 spill slot, and align it at the same
// time. Leave the stack slot address in the scratch register r4.
//
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
//
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
AFI->setShouldRestoreSPFromFP(true);
// sub r4, sp, #numregs * 8
// The immediate is <= 64, so it doesn't need any special encoding.
unsigned Opc = isThumb ? ARM::t2SUBri : ARM::SUBri;
BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addReg(ARM::SP)
.addImm(8 * NumAlignedDPRCS2Regs)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
Align MaxAlign = MF.getFrameInfo().getMaxAlign();
// We must set parameter MustBeSingleInstruction to true, since
// skipAlignedDPRCS2Spills expects exactly 3 instructions to perform
// stack alignment. Luckily, this can always be done since all ARM
// architecture versions that support Neon also support the BFC
// instruction.
emitAligningInstructions(MF, AFI, TII, MBB, MI, DL, ARM::R4, MaxAlign, true);
// mov sp, r4
// The stack pointer must be adjusted before spilling anything, otherwise
// the stack slots could be clobbered by an interrupt handler.
// Leave r4 live, it is used below.
Opc = isThumb ? ARM::tMOVr : ARM::MOVr;
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(Opc), ARM::SP)
.addReg(ARM::R4)
.add(predOps(ARMCC::AL));
if (!isThumb)
MIB.add(condCodeOp());
// Now spill NumAlignedDPRCS2Regs registers starting from d8.
// r4 holds the stack slot address.
unsigned NextReg = ARM::D8;
// 16-byte aligned vst1.64 with 4 d-regs and address writeback.
// The writeback is only needed when emitting two vst1.64 instructions.
if (NumAlignedDPRCS2Regs >= 6) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
MBB.addLiveIn(SupReg);
BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Qwb_fixed), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(16)
.addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vst1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
MBB.addLiveIn(SupReg);
BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Q))
.addReg(ARM::R4)
.addImm(16)
.addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vst1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QPRRegClass);
MBB.addLiveIn(SupReg);
BuildMI(MBB, MI, DL, TII.get(ARM::VST1q64))
.addReg(ARM::R4)
.addImm(16)
.addReg(SupReg)
.add(predOps(ARMCC::AL));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vstr.64 for the odd last register.
if (NumAlignedDPRCS2Regs) {
MBB.addLiveIn(NextReg);
// vstr.64 uses addrmode5 which has an offset scale of 4.
BuildMI(MBB, MI, DL, TII.get(ARM::VSTRD))
.addReg(NextReg)
.addReg(ARM::R4)
.addImm((NextReg - R4BaseReg) * 2)
.add(predOps(ARMCC::AL));
}
// The last spill instruction inserted should kill the scratch register r4.
std::prev(MI)->addRegisterKilled(ARM::R4, TRI);
}
/// Skip past the code inserted by emitAlignedDPRCS2Spills, and return an
/// iterator to the following instruction.
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs) {
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
++MI; ++MI; ++MI;
assert(MI->mayStore() && "Expecting spill instruction");
// These switches all fall through.
switch(NumAlignedDPRCS2Regs) {
case 7:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
LLVM_FALLTHROUGH;
default:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
LLVM_FALLTHROUGH;
case 1:
case 2:
case 4:
assert(MI->killsRegister(ARM::R4) && "Missed kill flag");
++MI;
}
return MI;
}
/// Emit aligned reload instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. These instructions are assumed to execute while the
/// stack is still aligned, unlike the code inserted by emitPopInst.
static void emitAlignedDPRCS2Restores(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
ArrayRef<CalleeSavedInfo> CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
// Find the frame index assigned to d8.
int D8SpillFI = 0;
for (unsigned i = 0, e = CSI.size(); i != e; ++i)
if (CSI[i].getReg() == ARM::D8) {
D8SpillFI = CSI[i].getFrameIdx();
break;
}
// Materialize the address of the d8 spill slot into the scratch register r4.
// This can be fairly complicated if the stack frame is large, so just use
// the normal frame index elimination mechanism to do it. This code runs as
// the initial part of the epilog where the stack and base pointers haven't
// been changed yet.
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
unsigned Opc = isThumb ? ARM::t2ADDri : ARM::ADDri;
BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addFrameIndex(D8SpillFI)
.addImm(0)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
// Now restore NumAlignedDPRCS2Regs registers starting from d8.
unsigned NextReg = ARM::D8;
// 16-byte aligned vld1.64 with 4 d-regs and writeback.
if (NumAlignedDPRCS2Regs >= 6) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Qwb_fixed), NextReg)
.addReg(ARM::R4, RegState::Define)
.addReg(ARM::R4, RegState::Kill)
.addImm(16)
.addReg(SupReg, RegState::ImplicitDefine)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vld1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QQPRRegClass);
BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Q), NextReg)
.addReg(ARM::R4)
.addImm(16)
.addReg(SupReg, RegState::ImplicitDefine)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vld1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
&ARM::QPRRegClass);
BuildMI(MBB, MI, DL, TII.get(ARM::VLD1q64), SupReg)
.addReg(ARM::R4)
.addImm(16)
.add(predOps(ARMCC::AL));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vldr.64 for the remaining odd register.
if (NumAlignedDPRCS2Regs)
BuildMI(MBB, MI, DL, TII.get(ARM::VLDRD), NextReg)
.addReg(ARM::R4)
.addImm(2 * (NextReg - R4BaseReg))
.add(predOps(ARMCC::AL));
// Last store kills r4.
std::prev(MI)->addRegisterKilled(ARM::R4, TRI);
}
bool ARMFrameLowering::spillCalleeSavedRegisters(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
unsigned PushOpc = AFI->isThumbFunction() ? ARM::t2STMDB_UPD : ARM::STMDB_UPD;
unsigned PushOneOpc = AFI->isThumbFunction() ?
ARM::t2STR_PRE : ARM::STR_PRE_IMM;
unsigned FltOpc = ARM::VSTMDDB_UPD;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
// Save the non-secure floating point context.
if (llvm::any_of(CSI, [](const CalleeSavedInfo &C) {
return C.getReg() == ARM::FPCXTNS;
})) {
BuildMI(MBB, MI, DebugLoc(), STI.getInstrInfo()->get(ARM::VSTR_FPCXTNS_pre),
ARM::SP)
.addReg(ARM::SP)
.addImm(-4)
.add(predOps(ARMCC::AL));
}
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea1Register, 0,
MachineInstr::FrameSetup);
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea2Register, 0,
MachineInstr::FrameSetup);
emitPushInst(MBB, MI, CSI, FltOpc, 0, true, &isARMArea3Register,
NumAlignedDPRCS2Regs, MachineInstr::FrameSetup);
// The code above does not insert spill code for the aligned DPRCS2 registers.
// The stack realignment code will be inserted between the push instructions
// and these spills.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Spills(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
return true;
}
bool ARMFrameLowering::restoreCalleeSavedRegisters(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
bool isVarArg = AFI->getArgRegsSaveSize() > 0;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
// The emitPopInst calls below do not insert reloads for the aligned DPRCS2
// registers. Do that here instead.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Restores(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
unsigned PopOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
unsigned LdrOpc = AFI->isThumbFunction() ? ARM::t2LDR_POST :ARM::LDR_POST_IMM;
unsigned FltOpc = ARM::VLDMDIA_UPD;
emitPopInst(MBB, MI, CSI, FltOpc, 0, isVarArg, true, &isARMArea3Register,
NumAlignedDPRCS2Regs);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
&isARMArea2Register, 0);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
&isARMArea1Register, 0);
return true;
}
// FIXME: Make generic?
static unsigned EstimateFunctionSizeInBytes(const MachineFunction &MF,
const ARMBaseInstrInfo &TII) {
unsigned FnSize = 0;
for (auto &MBB : MF) {
for (auto &MI : MBB)
FnSize += TII.getInstSizeInBytes(MI);
}
if (MF.getJumpTableInfo())
for (auto &Table: MF.getJumpTableInfo()->getJumpTables())
FnSize += Table.MBBs.size() * 4;
FnSize += MF.getConstantPool()->getConstants().size() * 4;
return FnSize;
}
/// estimateRSStackSizeLimit - Look at each instruction that references stack
/// frames and return the stack size limit beyond which some of these
/// instructions will require a scratch register during their expansion later.
// FIXME: Move to TII?
static unsigned estimateRSStackSizeLimit(MachineFunction &MF,
const TargetFrameLowering *TFI,
bool &HasNonSPFrameIndex) {
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
unsigned Limit = (1 << 12) - 1;
for (auto &MBB : MF) {
for (auto &MI : MBB) {
if (MI.isDebugInstr())
continue;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
if (!MI.getOperand(i).isFI())
continue;
// When using ADDri to get the address of a stack object, 255 is the
// largest offset guaranteed to fit in the immediate offset.
if (MI.getOpcode() == ARM::ADDri) {
Limit = std::min(Limit, (1U << 8) - 1);
break;
}
// t2ADDri will not require an extra register, it can reuse the
// destination.
if (MI.getOpcode() == ARM::t2ADDri || MI.getOpcode() == ARM::t2ADDri12)
break;
const MCInstrDesc &MCID = MI.getDesc();
const TargetRegisterClass *RegClass = TII.getRegClass(MCID, i, TRI, MF);
if (RegClass && !RegClass->contains(ARM::SP))
HasNonSPFrameIndex = true;
// Otherwise check the addressing mode.
switch (MI.getDesc().TSFlags & ARMII::AddrModeMask) {
case ARMII::AddrMode_i12:
case ARMII::AddrMode2:
// Default 12 bit limit.
break;
case ARMII::AddrMode3:
case ARMII::AddrModeT2_i8:
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode5FP16:
Limit = std::min(Limit, ((1U << 8) - 1) * 2);
break;
case ARMII::AddrMode5:
case ARMII::AddrModeT2_i8s4:
case ARMII::AddrModeT2_ldrex:
Limit = std::min(Limit, ((1U << 8) - 1) * 4);
break;
case ARMII::AddrModeT2_i12:
// i12 supports only positive offset so these will be converted to
// i8 opcodes. See llvm::rewriteT2FrameIndex.
if (TFI->hasFP(MF) && AFI->hasStackFrame())
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode4:
case ARMII::AddrMode6:
// Addressing modes 4 & 6 (load/store) instructions can't encode an
// immediate offset for stack references.
return 0;
case ARMII::AddrModeT2_i7:
Limit = std::min(Limit, ((1U << 7) - 1) * 1);
break;
case ARMII::AddrModeT2_i7s2:
Limit = std::min(Limit, ((1U << 7) - 1) * 2);
break;
case ARMII::AddrModeT2_i7s4:
Limit = std::min(Limit, ((1U << 7) - 1) * 4);
break;
default:
llvm_unreachable("Unhandled addressing mode in stack size limit calculation");
}
break; // At most one FI per instruction
}
}
}
return Limit;
}
// In functions that realign the stack, it can be an advantage to spill the
// callee-saved vector registers after realigning the stack. The vst1 and vld1
// instructions take alignment hints that can improve performance.
static void
checkNumAlignedDPRCS2Regs(MachineFunction &MF, BitVector &SavedRegs) {
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(0);
if (!SpillAlignedNEONRegs)
return;
// Naked functions don't spill callee-saved registers.
if (MF.getFunction().hasFnAttribute(Attribute::Naked))
return;
// We are planning to use NEON instructions vst1 / vld1.
if (!static_cast<const ARMSubtarget &>(MF.getSubtarget()).hasNEON())
return;
// Don't bother if the default stack alignment is sufficiently high.
if (MF.getSubtarget().getFrameLowering()->getStackAlign() >= Align(8))
return;
// Aligned spills require stack realignment.
if (!static_cast<const ARMBaseRegisterInfo *>(
MF.getSubtarget().getRegisterInfo())->canRealignStack(MF))
return;
// We always spill contiguous d-registers starting from d8. Count how many
// needs spilling. The register allocator will almost always use the
// callee-saved registers in order, but it can happen that there are holes in
// the range. Registers above the hole will be spilled to the standard DPRCS
// area.
unsigned NumSpills = 0;
for (; NumSpills < 8; ++NumSpills)
if (!SavedRegs.test(ARM::D8 + NumSpills))
break;
// Don't do this for just one d-register. It's not worth it.
if (NumSpills < 2)
return;
// Spill the first NumSpills D-registers after realigning the stack.
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(NumSpills);
// A scratch register is required for the vst1 / vld1 instructions.
SavedRegs.set(ARM::R4);
}
bool ARMFrameLowering::enableShrinkWrapping(const MachineFunction &MF) const {
// For CMSE entry functions, we want to save the FPCXT_NS immediately
// upon function entry (resp. restore it immmediately before return)
if (STI.hasV8_1MMainlineOps() &&
MF.getInfo<ARMFunctionInfo>()->isCmseNSEntryFunction())
return false;
return true;
}
void ARMFrameLowering::determineCalleeSaves(MachineFunction &MF,
BitVector &SavedRegs,
RegScavenger *RS) const {
TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
// This tells PEI to spill the FP as if it is any other callee-save register
// to take advantage the eliminateFrameIndex machinery. This also ensures it
// is spilled in the order specified by getCalleeSavedRegs() to make it easier
// to combine multiple loads / stores.
bool CanEliminateFrame = true;
bool CS1Spilled = false;
bool LRSpilled = false;
unsigned NumGPRSpills = 0;
unsigned NumFPRSpills = 0;
SmallVector<unsigned, 4> UnspilledCS1GPRs;
SmallVector<unsigned, 4> UnspilledCS2GPRs;
const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
MachineFrameInfo &MFI = MF.getFrameInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
(void)TRI; // Silence unused warning in non-assert builds.
Register FramePtr = RegInfo->getFrameRegister(MF);
// Spill R4 if Thumb2 function requires stack realignment - it will be used as
// scratch register. Also spill R4 if Thumb2 function has varsized objects,
// since it's not always possible to restore sp from fp in a single
// instruction.
// FIXME: It will be better just to find spare register here.
if (AFI->isThumb2Function() &&
(MFI.hasVarSizedObjects() || RegInfo->hasStackRealignment(MF)))
SavedRegs.set(ARM::R4);
// If a stack probe will be emitted, spill R4 and LR, since they are
// clobbered by the stack probe call.
// This estimate should be a safe, conservative estimate. The actual
// stack probe is enabled based on the size of the local objects;
// this estimate also includes the varargs store size.
if (STI.isTargetWindows() &&
WindowsRequiresStackProbe(MF, MFI.estimateStackSize(MF))) {
SavedRegs.set(ARM::R4);
SavedRegs.set(ARM::LR);
}
if (AFI->isThumb1OnlyFunction()) {
// Spill LR if Thumb1 function uses variable length argument lists.
if (AFI->getArgRegsSaveSize() > 0)
SavedRegs.set(ARM::LR);
// Spill R4 if Thumb1 epilogue has to restore SP from FP or the function
// requires stack alignment. We don't know for sure what the stack size
// will be, but for this, an estimate is good enough. If there anything
// changes it, it'll be a spill, which implies we've used all the registers
// and so R4 is already used, so not marking it here will be OK.
// FIXME: It will be better just to find spare register here.
if (MFI.hasVarSizedObjects() || RegInfo->hasStackRealignment(MF) ||
MFI.estimateStackSize(MF) > 508)
SavedRegs.set(ARM::R4);
}
// See if we can spill vector registers to aligned stack.
checkNumAlignedDPRCS2Regs(MF, SavedRegs);
// Spill the BasePtr if it's used.
if (RegInfo->hasBasePointer(MF))
SavedRegs.set(RegInfo->getBaseRegister());
// On v8.1-M.Main CMSE entry functions save/restore FPCXT.
if (STI.hasV8_1MMainlineOps() && AFI->isCmseNSEntryFunction())
CanEliminateFrame = false;
// Don't spill FP if the frame can be eliminated. This is determined
// by scanning the callee-save registers to see if any is modified.
const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF);
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
bool Spilled = false;
if (SavedRegs.test(Reg)) {
Spilled = true;
CanEliminateFrame = false;
}
if (!ARM::GPRRegClass.contains(Reg)) {
if (Spilled) {
if (ARM::SPRRegClass.contains(Reg))
NumFPRSpills++;
else if (ARM::DPRRegClass.contains(Reg))
NumFPRSpills += 2;
else if (ARM::QPRRegClass.contains(Reg))
NumFPRSpills += 4;
}
continue;
}
if (Spilled) {
NumGPRSpills++;
if (!STI.splitFramePushPop(MF)) {
if (Reg == ARM::LR)
LRSpilled = true;
CS1Spilled = true;
continue;
}
// Keep track if LR and any of R4, R5, R6, and R7 is spilled.
switch (Reg) {
case ARM::LR:
LRSpilled = true;
LLVM_FALLTHROUGH;
case ARM::R0: case ARM::R1:
case ARM::R2: case ARM::R3:
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
CS1Spilled = true;
break;
default:
break;
}
} else {
if (!STI.splitFramePushPop(MF)) {
UnspilledCS1GPRs.push_back(Reg);
continue;
}
switch (Reg) {
case ARM::R0: case ARM::R1:
case ARM::R2: case ARM::R3:
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
case ARM::LR:
UnspilledCS1GPRs.push_back(Reg);
break;
default:
UnspilledCS2GPRs.push_back(Reg);
break;
}
}
}
bool ForceLRSpill = false;
if (!LRSpilled && AFI->isThumb1OnlyFunction()) {
unsigned FnSize = EstimateFunctionSizeInBytes(MF, TII);
// Force LR to be spilled if the Thumb function size is > 2048. This enables
// use of BL to implement far jump.
if (FnSize >= (1 << 11)) {
CanEliminateFrame = false;
ForceLRSpill = true;
}
}
// If any of the stack slot references may be out of range of an immediate
// offset, make sure a register (or a spill slot) is available for the
// register scavenger. Note that if we're indexing off the frame pointer, the
// effective stack size is 4 bytes larger since the FP points to the stack
// slot of the previous FP. Also, if we have variable sized objects in the
// function, stack slot references will often be negative, and some of
// our instructions are positive-offset only, so conservatively consider
// that case to want a spill slot (or register) as well. Similarly, if
// the function adjusts the stack pointer during execution and the
// adjustments aren't already part of our stack size estimate, our offset
// calculations may be off, so be conservative.
// FIXME: We could add logic to be more precise about negative offsets
// and which instructions will need a scratch register for them. Is it
// worth the effort and added fragility?
unsigned EstimatedStackSize =
MFI.estimateStackSize(MF) + 4 * (NumGPRSpills + NumFPRSpills);
// Determine biggest (positive) SP offset in MachineFrameInfo.
int MaxFixedOffset = 0;
for (int I = MFI.getObjectIndexBegin(); I < 0; ++I) {
int MaxObjectOffset = MFI.getObjectOffset(I) + MFI.getObjectSize(I);
MaxFixedOffset = std::max(MaxFixedOffset, MaxObjectOffset);
}
bool HasFP = hasFP(MF);
if (HasFP) {
if (AFI->hasStackFrame())
EstimatedStackSize += 4;
} else {
// If FP is not used, SP will be used to access arguments, so count the
// size of arguments into the estimation.
EstimatedStackSize += MaxFixedOffset;
}
EstimatedStackSize += 16; // For possible paddings.
unsigned EstimatedRSStackSizeLimit, EstimatedRSFixedSizeLimit;
bool HasNonSPFrameIndex = false;
if (AFI->isThumb1OnlyFunction()) {
// For Thumb1, don't bother to iterate over the function. The only
// instruction that requires an emergency spill slot is a store to a
// frame index.
//
// tSTRspi, which is used for sp-relative accesses, has an 8-bit unsigned
// immediate. tSTRi, which is used for bp- and fp-relative accesses, has
// a 5-bit unsigned immediate.
//
// We could try to check if the function actually contains a tSTRspi
// that might need the spill slot, but it's not really important.
// Functions with VLAs or extremely large call frames are rare, and
// if a function is allocating more than 1KB of stack, an extra 4-byte
// slot probably isn't relevant.
if (RegInfo->hasBasePointer(MF))
EstimatedRSStackSizeLimit = (1U << 5) * 4;
else
EstimatedRSStackSizeLimit = (1U << 8) * 4;
EstimatedRSFixedSizeLimit = (1U << 5) * 4;
} else {
EstimatedRSStackSizeLimit =
estimateRSStackSizeLimit(MF, this, HasNonSPFrameIndex);
EstimatedRSFixedSizeLimit = EstimatedRSStackSizeLimit;
}
// Final estimate of whether sp or bp-relative accesses might require
// scavenging.
bool HasLargeStack = EstimatedStackSize > EstimatedRSStackSizeLimit;
// If the stack pointer moves and we don't have a base pointer, the
// estimate logic doesn't work. The actual offsets might be larger when
// we're constructing a call frame, or we might need to use negative
// offsets from fp.
bool HasMovingSP = MFI.hasVarSizedObjects() ||
(MFI.adjustsStack() && !canSimplifyCallFramePseudos(MF));
bool HasBPOrFixedSP = RegInfo->hasBasePointer(MF) || !HasMovingSP;
// If we have a frame pointer, we assume arguments will be accessed
// relative to the frame pointer. Check whether fp-relative accesses to
// arguments require scavenging.
//
// We could do slightly better on Thumb1; in some cases, an sp-relative
// offset would be legal even though an fp-relative offset is not.
int MaxFPOffset = getMaxFPOffset(STI, *AFI);
bool HasLargeArgumentList =
HasFP && (MaxFixedOffset - MaxFPOffset) > (int)EstimatedRSFixedSizeLimit;
bool BigFrameOffsets = HasLargeStack || !HasBPOrFixedSP ||
HasLargeArgumentList || HasNonSPFrameIndex;
LLVM_DEBUG(dbgs() << "EstimatedLimit: " << EstimatedRSStackSizeLimit
<< "; EstimatedStack: " << EstimatedStackSize
<< "; EstimatedFPStack: " << MaxFixedOffset - MaxFPOffset
<< "; BigFrameOffsets: " << BigFrameOffsets << "\n");
if (BigFrameOffsets ||
!CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) {
AFI->setHasStackFrame(true);
if (HasFP) {
SavedRegs.set(FramePtr);
// If the frame pointer is required by the ABI, also spill LR so that we
// emit a complete frame record.
if (MF.getTarget().Options.DisableFramePointerElim(MF) && !LRSpilled) {
SavedRegs.set(ARM::LR);
LRSpilled = true;
NumGPRSpills++;
auto LRPos = llvm::find(UnspilledCS1GPRs, ARM::LR);
if (LRPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(LRPos);
}
auto FPPos = llvm::find(UnspilledCS1GPRs, FramePtr);
if (FPPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(FPPos);
NumGPRSpills++;
if (FramePtr == ARM::R7)
CS1Spilled = true;
}
// This is true when we inserted a spill for a callee-save GPR which is
// not otherwise used by the function. This guaranteees it is possible
// to scavenge a register to hold the address of a stack slot. On Thumb1,
// the register must be a valid operand to tSTRi, i.e. r4-r7. For other
// subtargets, this is any GPR, i.e. r4-r11 or lr.
//
// If we don't insert a spill, we instead allocate an emergency spill
// slot, which can be used by scavenging to spill an arbitrary register.
//
// We currently don't try to figure out whether any specific instruction
// requires scavening an additional register.
bool ExtraCSSpill = false;
if (AFI->isThumb1OnlyFunction()) {
// For Thumb1-only targets, we need some low registers when we save and
// restore the high registers (which aren't allocatable, but could be
// used by inline assembly) because the push/pop instructions can not
// access high registers. If necessary, we might need to push more low
// registers to ensure that there is at least one free that can be used
// for the saving & restoring, and preferably we should ensure that as
// many as are needed are available so that fewer push/pop instructions
// are required.
// Low registers which are not currently pushed, but could be (r4-r7).
SmallVector<unsigned, 4> AvailableRegs;
// Unused argument registers (r0-r3) can be clobbered in the prologue for
// free.
int EntryRegDeficit = 0;
for (unsigned Reg : {ARM::R0, ARM::R1, ARM::R2, ARM::R3}) {
if (!MF.getRegInfo().isLiveIn(Reg)) {
--EntryRegDeficit;
LLVM_DEBUG(dbgs()
<< printReg(Reg, TRI)
<< " is unused argument register, EntryRegDeficit = "
<< EntryRegDeficit << "\n");
}
}
// Unused return registers can be clobbered in the epilogue for free.
int ExitRegDeficit = AFI->getReturnRegsCount() - 4;
LLVM_DEBUG(dbgs() << AFI->getReturnRegsCount()
<< " return regs used, ExitRegDeficit = "
<< ExitRegDeficit << "\n");
int RegDeficit = std::max(EntryRegDeficit, ExitRegDeficit);
LLVM_DEBUG(dbgs() << "RegDeficit = " << RegDeficit << "\n");
// r4-r6 can be used in the prologue if they are pushed by the first push
// instruction.
for (unsigned Reg : {ARM::R4, ARM::R5, ARM::R6}) {
if (SavedRegs.test(Reg)) {
--RegDeficit;
LLVM_DEBUG(dbgs() << printReg(Reg, TRI)
<< " is saved low register, RegDeficit = "
<< RegDeficit << "\n");
} else {
AvailableRegs.push_back(Reg);
LLVM_DEBUG(
dbgs()
<< printReg(Reg, TRI)
<< " is non-saved low register, adding to AvailableRegs\n");
}
}
// r7 can be used if it is not being used as the frame pointer.
if (!HasFP) {
if (SavedRegs.test(ARM::R7)) {
--RegDeficit;
LLVM_DEBUG(dbgs() << "%r7 is saved low register, RegDeficit = "
<< RegDeficit << "\n");
} else {
AvailableRegs.push_back(ARM::R7);
LLVM_DEBUG(
dbgs()
<< "%r7 is non-saved low register, adding to AvailableRegs\n");
}
}
// Each of r8-r11 needs to be copied to a low register, then pushed.
for (unsigned Reg : {ARM::R8, ARM::R9, ARM::R10, ARM::R11}) {
if (SavedRegs.test(Reg)) {
++RegDeficit;
LLVM_DEBUG(dbgs() << printReg(Reg, TRI)
<< " is saved high register, RegDeficit = "
<< RegDeficit << "\n");
}
}
// LR can only be used by PUSH, not POP, and can't be used at all if the
// llvm.returnaddress intrinsic is used. This is only worth doing if we
// are more limited at function entry than exit.
if ((EntryRegDeficit > ExitRegDeficit) &&
!(MF.getRegInfo().isLiveIn(ARM::LR) &&
MF.getFrameInfo().isReturnAddressTaken())) {
if (SavedRegs.test(ARM::LR)) {
--RegDeficit;
LLVM_DEBUG(dbgs() << "%lr is saved register, RegDeficit = "
<< RegDeficit << "\n");
} else {
AvailableRegs.push_back(ARM::LR);
LLVM_DEBUG(dbgs() << "%lr is not saved, adding to AvailableRegs\n");
}
}
// If there are more high registers that need pushing than low registers
// available, push some more low registers so that we can use fewer push
// instructions. This might not reduce RegDeficit all the way to zero,
// because we can only guarantee that r4-r6 are available, but r8-r11 may
// need saving.
LLVM_DEBUG(dbgs() << "Final RegDeficit = " << RegDeficit << "\n");
for (; RegDeficit > 0 && !AvailableRegs.empty(); --RegDeficit) {
unsigned Reg = AvailableRegs.pop_back_val();
LLVM_DEBUG(dbgs() << "Spilling " << printReg(Reg, TRI)
<< " to make up reg deficit\n");
SavedRegs.set(Reg);
NumGPRSpills++;
CS1Spilled = true;
assert(!MRI.isReserved(Reg) && "Should not be reserved");
if (Reg != ARM::LR && !MRI.isPhysRegUsed(Reg))
ExtraCSSpill = true;
UnspilledCS1GPRs.erase(llvm::find(UnspilledCS1GPRs, Reg));
if (Reg == ARM::LR)
LRSpilled = true;
}
LLVM_DEBUG(dbgs() << "After adding spills, RegDeficit = " << RegDeficit
<< "\n");
}
// Avoid spilling LR in Thumb1 if there's a tail call: it's expensive to
// restore LR in that case.
bool ExpensiveLRRestore = AFI->isThumb1OnlyFunction() && MFI.hasTailCall();
// If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
// Spill LR as well so we can fold BX_RET to the registers restore (LDM).
if (!LRSpilled && CS1Spilled && !ExpensiveLRRestore) {
SavedRegs.set(ARM::LR);
NumGPRSpills++;
SmallVectorImpl<unsigned>::iterator LRPos;
LRPos = llvm::find(UnspilledCS1GPRs, (unsigned)ARM::LR);
if (LRPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(LRPos);
ForceLRSpill = false;
if (!MRI.isReserved(ARM::LR) && !MRI.isPhysRegUsed(ARM::LR) &&
!AFI->isThumb1OnlyFunction())
ExtraCSSpill = true;
}
// If stack and double are 8-byte aligned and we are spilling an odd number
// of GPRs, spill one extra callee save GPR so we won't have to pad between
// the integer and double callee save areas.
LLVM_DEBUG(dbgs() << "NumGPRSpills = " << NumGPRSpills << "\n");
const Align TargetAlign = getStackAlign();
if (TargetAlign >= Align(8) && (NumGPRSpills & 1)) {
if (CS1Spilled && !UnspilledCS1GPRs.empty()) {
for (unsigned i = 0, e = UnspilledCS1GPRs.size(); i != e; ++i) {
unsigned Reg = UnspilledCS1GPRs[i];
// Don't spill high register if the function is thumb. In the case of
// Windows on ARM, accept R11 (frame pointer)
if (!AFI->isThumbFunction() ||
(STI.isTargetWindows() && Reg == ARM::R11) ||
isARMLowRegister(Reg) ||
(Reg == ARM::LR && !ExpensiveLRRestore)) {
SavedRegs.set(Reg);
LLVM_DEBUG(dbgs() << "Spilling " << printReg(Reg, TRI)
<< " to make up alignment\n");
if (!MRI.isReserved(Reg) && !MRI.isPhysRegUsed(Reg) &&
!(Reg == ARM::LR && AFI->isThumb1OnlyFunction()))
ExtraCSSpill = true;
break;
}
}
} else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) {
unsigned Reg = UnspilledCS2GPRs.front();
SavedRegs.set(Reg);
LLVM_DEBUG(dbgs() << "Spilling " << printReg(Reg, TRI)
<< " to make up alignment\n");
if (!MRI.isReserved(Reg) && !MRI.isPhysRegUsed(Reg))
ExtraCSSpill = true;
}
}
// Estimate if we might need to scavenge a register at some point in order
// to materialize a stack offset. If so, either spill one additional
// callee-saved register or reserve a special spill slot to facilitate
// register scavenging. Thumb1 needs a spill slot for stack pointer
// adjustments also, even when the frame itself is small.
if (BigFrameOffsets && !ExtraCSSpill) {
// If any non-reserved CS register isn't spilled, just spill one or two
// extra. That should take care of it!
unsigned NumExtras = TargetAlign.value() / 4;
SmallVector<unsigned, 2> Extras;
while (NumExtras && !UnspilledCS1GPRs.empty()) {
unsigned Reg = UnspilledCS1GPRs.pop_back_val();
if (!MRI.isReserved(Reg) &&
(!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg))) {
Extras.push_back(Reg);
NumExtras--;
}
}
// For non-Thumb1 functions, also check for hi-reg CS registers
if (!AFI->isThumb1OnlyFunction()) {
while (NumExtras && !UnspilledCS2GPRs.empty()) {
unsigned Reg = UnspilledCS2GPRs.pop_back_val();
if (!MRI.isReserved(Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
}
if (NumExtras == 0) {
for (unsigned Reg : Extras) {
SavedRegs.set(Reg);
if (!MRI.isPhysRegUsed(Reg))
ExtraCSSpill = true;
}
}
if (!ExtraCSSpill && RS) {
// Reserve a slot closest to SP or frame pointer.
LLVM_DEBUG(dbgs() << "Reserving emergency spill slot\n");
const TargetRegisterClass &RC = ARM::GPRRegClass;
unsigned Size = TRI->getSpillSize(RC);
Align Alignment = TRI->getSpillAlign(RC);
RS->addScavengingFrameIndex(
MFI.CreateStackObject(Size, Alignment, false));
}
}
}
if (ForceLRSpill)
SavedRegs.set(ARM::LR);
AFI->setLRIsSpilled(SavedRegs.test(ARM::LR));
}
void ARMFrameLowering::getCalleeSaves(const MachineFunction &MF,
BitVector &SavedRegs) const {
TargetFrameLowering::getCalleeSaves(MF, SavedRegs);
// If we have the "returned" parameter attribute which guarantees that we
// return the value which was passed in r0 unmodified (e.g. C++ 'structors),
// record that fact for IPRA.
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
if (AFI->getPreservesR0())
SavedRegs.set(ARM::R0);
}
bool ARMFrameLowering::assignCalleeSavedSpillSlots(
MachineFunction &MF, const TargetRegisterInfo *TRI,
std::vector<CalleeSavedInfo> &CSI) const {
// For CMSE entry functions, handle floating-point context as if it was a
// callee-saved register.
if (STI.hasV8_1MMainlineOps() &&
MF.getInfo<ARMFunctionInfo>()->isCmseNSEntryFunction()) {
CSI.emplace_back(ARM::FPCXTNS);
CSI.back().setRestored(false);
}
return false;
}
const TargetFrameLowering::SpillSlot *
ARMFrameLowering::getCalleeSavedSpillSlots(unsigned &NumEntries) const {
static const SpillSlot FixedSpillOffsets[] = {{ARM::FPCXTNS, -4}};
NumEntries = array_lengthof(FixedSpillOffsets);
return FixedSpillOffsets;
}
MachineBasicBlock::iterator ARMFrameLowering::eliminateCallFramePseudoInstr(
MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
bool isARM = !AFI->isThumbFunction();
DebugLoc dl = I->getDebugLoc();
unsigned Opc = I->getOpcode();
bool IsDestroy = Opc == TII.getCallFrameDestroyOpcode();
unsigned CalleePopAmount = IsDestroy ? I->getOperand(1).getImm() : 0;
assert(!AFI->isThumb1OnlyFunction() &&
"This eliminateCallFramePseudoInstr does not support Thumb1!");
int PIdx = I->findFirstPredOperandIdx();
ARMCC::CondCodes Pred = (PIdx == -1)
? ARMCC::AL
: (ARMCC::CondCodes)I->getOperand(PIdx).getImm();
unsigned PredReg = TII.getFramePred(*I);
if (!hasReservedCallFrame(MF)) {
// Bail early if the callee is expected to do the adjustment.
if (IsDestroy && CalleePopAmount != -1U)
return MBB.erase(I);
// If we have alloca, convert as follows:
// ADJCALLSTACKDOWN -> sub, sp, sp, amount
// ADJCALLSTACKUP -> add, sp, sp, amount
unsigned Amount = TII.getFrameSize(*I);
if (Amount != 0) {
// We need to keep the stack aligned properly. To do this, we round the
// amount of space needed for the outgoing arguments up to the next
// alignment boundary.
Amount = alignSPAdjust(Amount);
if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) {
emitSPUpdate(isARM, MBB, I, dl, TII, -Amount, MachineInstr::NoFlags,
Pred, PredReg);
} else {
assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP);
emitSPUpdate(isARM, MBB, I, dl, TII, Amount, MachineInstr::NoFlags,
Pred, PredReg);
}
}
} else if (CalleePopAmount != -1U) {
// If the calling convention demands that the callee pops arguments from the
// stack, we want to add it back if we have a reserved call frame.
emitSPUpdate(isARM, MBB, I, dl, TII, -CalleePopAmount,
MachineInstr::NoFlags, Pred, PredReg);
}
return MBB.erase(I);
}
/// Get the minimum constant for ARM that is greater than or equal to the
/// argument. In ARM, constants can have any value that can be produced by
/// rotating an 8-bit value to the right by an even number of bits within a
/// 32-bit word.
static uint32_t alignToARMConstant(uint32_t Value) {
unsigned Shifted = 0;
if (Value == 0)
return 0;
while (!(Value & 0xC0000000)) {
Value = Value << 2;
Shifted += 2;
}
bool Carry = (Value & 0x00FFFFFF);
Value = ((Value & 0xFF000000) >> 24) + Carry;
if (Value & 0x0000100)
Value = Value & 0x000001FC;
if (Shifted > 24)
Value = Value >> (Shifted - 24);
else
Value = Value << (24 - Shifted);
return Value;
}
// The stack limit in the TCB is set to this many bytes above the actual
// stack limit.
static const uint64_t kSplitStackAvailable = 256;
// Adjust the function prologue to enable split stacks. This currently only
// supports android and linux.
//
// The ABI of the segmented stack prologue is a little arbitrarily chosen, but
// must be well defined in order to allow for consistent implementations of the
// __morestack helper function. The ABI is also not a normal ABI in that it
// doesn't follow the normal calling conventions because this allows the
// prologue of each function to be optimized further.
//
// Currently, the ABI looks like (when calling __morestack)
//
// * r4 holds the minimum stack size requested for this function call
// * r5 holds the stack size of the arguments to the function
// * the beginning of the function is 3 instructions after the call to
// __morestack
//
// Implementations of __morestack should use r4 to allocate a new stack, r5 to
// place the arguments on to the new stack, and the 3-instruction knowledge to
// jump directly to the body of the function when working on the new stack.
//
// An old (and possibly no longer compatible) implementation of __morestack for
// ARM can be found at [1].
//
// [1] - https://github.com/mozilla/rust/blob/86efd9/src/rt/arch/arm/morestack.S
void ARMFrameLowering::adjustForSegmentedStacks(
MachineFunction &MF, MachineBasicBlock &PrologueMBB) const {
unsigned Opcode;
unsigned CFIIndex;
const ARMSubtarget *ST = &MF.getSubtarget<ARMSubtarget>();
bool Thumb = ST->isThumb();
// Sadly, this currently doesn't support varargs, platforms other than
// android/linux. Note that thumb1/thumb2 are support for android/linux.
if (MF.getFunction().isVarArg())
report_fatal_error("Segmented stacks do not support vararg functions.");
if (!ST->isTargetAndroid() && !ST->isTargetLinux())
report_fatal_error("Segmented stacks not supported on this platform.");
MachineFrameInfo &MFI = MF.getFrameInfo();
MachineModuleInfo &MMI = MF.getMMI();
MCContext &Context = MMI.getContext();
const MCRegisterInfo *MRI = Context.getRegisterInfo();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
ARMFunctionInfo *ARMFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL;
uint64_t StackSize = MFI.getStackSize();
// Do not generate a prologue for leaf functions with a stack of size zero.
// For non-leaf functions we have to allow for the possibility that the
// callis to a non-split function, as in PR37807. This function could also
// take the address of a non-split function. When the linker tries to adjust
// its non-existent prologue, it would fail with an error. Mark the object
// file so that such failures are not errors. See this Go language bug-report
// https://go-review.googlesource.com/c/go/+/148819/
if (StackSize == 0 && !MFI.hasTailCall()) {
MF.getMMI().setHasNosplitStack(true);
return;
}
// Use R4 and R5 as scratch registers.
// We save R4 and R5 before use and restore them before leaving the function.
unsigned ScratchReg0 = ARM::R4;
unsigned ScratchReg1 = ARM::R5;
uint64_t AlignedStackSize;
MachineBasicBlock *PrevStackMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *PostStackMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *AllocMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *GetMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *McrMBB = MF.CreateMachineBasicBlock();
// Grab everything that reaches PrologueMBB to update there liveness as well.
SmallPtrSet<MachineBasicBlock *, 8> BeforePrologueRegion;
SmallVector<MachineBasicBlock *, 2> WalkList;
WalkList.push_back(&PrologueMBB);
do {
MachineBasicBlock *CurMBB = WalkList.pop_back_val();
for (MachineBasicBlock *PredBB : CurMBB->predecessors()) {
if (BeforePrologueRegion.insert(PredBB).second)
WalkList.push_back(PredBB);
}
} while (!WalkList.empty());
// The order in that list is important.
// The blocks will all be inserted before PrologueMBB using that order.
// Therefore the block that should appear first in the CFG should appear
// first in the list.
MachineBasicBlock *AddedBlocks[] = {PrevStackMBB, McrMBB, GetMBB, AllocMBB,
PostStackMBB};
for (MachineBasicBlock *B : AddedBlocks)
BeforePrologueRegion.insert(B);
for (const auto &LI : PrologueMBB.liveins()) {
for (MachineBasicBlock *PredBB : BeforePrologueRegion)
PredBB->addLiveIn(LI);
}
// Remove the newly added blocks from the list, since we know
// we do not have to do the following updates for them.
for (MachineBasicBlock *B : AddedBlocks) {
BeforePrologueRegion.erase(B);
MF.insert(PrologueMBB.getIterator(), B);
}
for (MachineBasicBlock *MBB : BeforePrologueRegion) {
// Make sure the LiveIns are still sorted and unique.
MBB->sortUniqueLiveIns();
// Replace the edges to PrologueMBB by edges to the sequences
// we are about to add.
MBB->ReplaceUsesOfBlockWith(&PrologueMBB, AddedBlocks[0]);
}
// The required stack size that is aligned to ARM constant criterion.
AlignedStackSize = alignToARMConstant(StackSize);
// When the frame size is less than 256 we just compare the stack
// boundary directly to the value of the stack pointer, per gcc.
bool CompareStackPointer = AlignedStackSize < kSplitStackAvailable;
// We will use two of the callee save registers as scratch registers so we
// need to save those registers onto the stack.
// We will use SR0 to hold stack limit and SR1 to hold the stack size
// requested and arguments for __morestack().
// SR0: Scratch Register #0
// SR1: Scratch Register #1
// push {SR0, SR1}
if (Thumb) {
BuildMI(PrevStackMBB, DL, TII.get(ARM::tPUSH))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
BuildMI(PrevStackMBB, DL, TII.get(ARM::STMDB_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Emit the relevant DWARF information about the change in stack pointer as
// well as where to find both r4 and r5 (the callee-save registers)
CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, 8));
BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(ScratchReg1, true), -4));
BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(ScratchReg0, true), -8));
BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// mov SR1, sp
if (Thumb) {
BuildMI(McrMBB, DL, TII.get(ARM::tMOVr), ScratchReg1)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL));
} else if (CompareStackPointer) {
BuildMI(McrMBB, DL, TII.get(ARM::MOVr), ScratchReg1)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
// sub SR1, sp, #StackSize
if (!CompareStackPointer && Thumb) {
BuildMI(McrMBB, DL, TII.get(ARM::tSUBi8), ScratchReg1)
.add(condCodeOp())
.addReg(ScratchReg1)
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL));
} else if (!CompareStackPointer) {
BuildMI(McrMBB, DL, TII.get(ARM::SUBri), ScratchReg1)
.addReg(ARM::SP)
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
if (Thumb && ST->isThumb1Only()) {
unsigned PCLabelId = ARMFI->createPICLabelUId();
ARMConstantPoolValue *NewCPV = ARMConstantPoolSymbol::Create(
MF.getFunction().getContext(), "__STACK_LIMIT", PCLabelId, 0);
MachineConstantPool *MCP = MF.getConstantPool();
unsigned CPI = MCP->getConstantPoolIndex(NewCPV, Align(4));
// ldr SR0, [pc, offset(STACK_LIMIT)]
BuildMI(GetMBB, DL, TII.get(ARM::tLDRpci), ScratchReg0)
.addConstantPoolIndex(CPI)
.add(predOps(ARMCC::AL));
// ldr SR0, [SR0]
BuildMI(GetMBB, DL, TII.get(ARM::tLDRi), ScratchReg0)
.addReg(ScratchReg0)
.addImm(0)
.add(predOps(ARMCC::AL));
} else {
// Get TLS base address from the coprocessor
// mrc p15, #0, SR0, c13, c0, #3
BuildMI(McrMBB, DL, TII.get(Thumb ? ARM::t2MRC : ARM::MRC),
ScratchReg0)
.addImm(15)
.addImm(0)
.addImm(13)
.addImm(0)
.addImm(3)
.add(predOps(ARMCC::AL));
// Use the last tls slot on android and a private field of the TCP on linux.
assert(ST->isTargetAndroid() || ST->isTargetLinux());
unsigned TlsOffset = ST->isTargetAndroid() ? 63 : 1;
// Get the stack limit from the right offset
// ldr SR0, [sr0, #4 * TlsOffset]
BuildMI(GetMBB, DL, TII.get(Thumb ? ARM::t2LDRi12 : ARM::LDRi12),
ScratchReg0)
.addReg(ScratchReg0)
.addImm(4 * TlsOffset)
.add(predOps(ARMCC::AL));
}
// Compare stack limit with stack size requested.
// cmp SR0, SR1
Opcode = Thumb ? ARM::tCMPr : ARM::CMPrr;
BuildMI(GetMBB, DL, TII.get(Opcode))
.addReg(ScratchReg0)
.addReg(ScratchReg1)
.add(predOps(ARMCC::AL));
// This jump is taken if StackLimit < SP - stack required.
Opcode = Thumb ? ARM::tBcc : ARM::Bcc;
BuildMI(GetMBB, DL, TII.get(Opcode)).addMBB(PostStackMBB)
.addImm(ARMCC::LO)
.addReg(ARM::CPSR);
// Calling __morestack(StackSize, Size of stack arguments).
// __morestack knows that the stack size requested is in SR0(r4)
// and amount size of stack arguments is in SR1(r5).
// Pass first argument for the __morestack by Scratch Register #0.
// The amount size of stack required
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8), ScratchReg0)
.add(condCodeOp())
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL));
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg0)
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
// Pass second argument for the __morestack by Scratch Register #1.
// The amount size of stack consumed to save function arguments.
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8), ScratchReg1)
.add(condCodeOp())
.addImm(alignToARMConstant(ARMFI->getArgumentStackSize()))
.add(predOps(ARMCC::AL));
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg1)
.addImm(alignToARMConstant(ARMFI->getArgumentStackSize()))
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
// push {lr} - Save return address of this function.
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tPUSH))
.add(predOps(ARMCC::AL))
.addReg(ARM::LR);
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::STMDB_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ARM::LR);
}
// Emit the DWARF info about the change in stack as well as where to find the
// previous link register
CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, 12));
BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(ARM::LR, true), -12));
BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// Call __morestack().
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tBL))
.add(predOps(ARMCC::AL))
.addExternalSymbol("__morestack");
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::BL))
.addExternalSymbol("__morestack");
}
// pop {lr} - Restore return address of this original function.
if (Thumb) {
if (ST->isThumb1Only()) {
BuildMI(AllocMBB, DL, TII.get(ARM::tPOP))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0);
BuildMI(AllocMBB, DL, TII.get(ARM::tMOVr), ARM::LR)
.addReg(ScratchReg0)
.add(predOps(ARMCC::AL));
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::t2LDR_POST))
.addReg(ARM::LR, RegState::Define)
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.addImm(4)
.add(predOps(ARMCC::AL));
}
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ARM::LR);
}
// Restore SR0 and SR1 in case of __morestack() was called.
// __morestack() will skip PostStackMBB block so we need to restore
// scratch registers from here.
// pop {SR0, SR1}
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tPOP))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Update the CFA offset now that we've popped
CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, 0));
BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// Return from this function.
BuildMI(AllocMBB, DL, TII.get(ST->getReturnOpcode())).add(predOps(ARMCC::AL));
// Restore SR0 and SR1 in case of __morestack() was not called.
// pop {SR0, SR1}
if (Thumb) {
BuildMI(PostStackMBB, DL, TII.get(ARM::tPOP))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
BuildMI(PostStackMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Update the CFA offset now that we've popped
CFIIndex = MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, 0));
BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// Tell debuggers that r4 and r5 are now the same as they were in the
// previous function, that they're the "Same Value".
CFIIndex = MF.addFrameInst(MCCFIInstruction::createSameValue(
nullptr, MRI->getDwarfRegNum(ScratchReg0, true)));
BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MF.addFrameInst(MCCFIInstruction::createSameValue(
nullptr, MRI->getDwarfRegNum(ScratchReg1, true)));
BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// Organizing MBB lists
PostStackMBB->addSuccessor(&PrologueMBB);
AllocMBB->addSuccessor(PostStackMBB);
GetMBB->addSuccessor(PostStackMBB);
GetMBB->addSuccessor(AllocMBB);
McrMBB->addSuccessor(GetMBB);
PrevStackMBB->addSuccessor(McrMBB);
#ifdef EXPENSIVE_CHECKS
MF.verify();
#endif
}
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