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llvm-mirror/lib/Target/ARM/ARMFrameLowering.cpp
Guillaume Chatelet 177d202096 [Alignment][NFC] Migrate AArch64, ARM, Hexagon, MSP and NVPTX backends to Align 
This patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

Differential Revision: https://reviews.llvm.org/D82749
2020-06-30 07:56:17 +00:00

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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.
//
//===----------------------------------------------------------------------===//
#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->needsStackRealignment(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();
}
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->needsStackRealignment(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();
unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize();
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 - ArgRegsSaveSize != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes - ArgRegsSaveSize,
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 -= (ArgRegsSaveSize +
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 (ArgRegsSaveSize)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, ArgRegsSaveSize,
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.
int ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
Register &FrameReg) const {
return 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->needsStackRealignment(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 && STI.hasV5TOps()) {
if (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);
} else
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
}
// 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->needsStackRealignment(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->needsStackRealignment(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.back();
UnspilledCS1GPRs.pop_back();
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.back();
UnspilledCS2GPRs.pop_back();
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());
if (!hasReservedCallFrame(MF)) {
// If we have alloca, convert as follows:
// ADJCALLSTACKDOWN -> sub, sp, sp, amount
// ADJCALLSTACKUP -> add, sp, sp, amount
MachineInstr &Old = *I;
DebugLoc dl = Old.getDebugLoc();
unsigned Amount = TII.getFrameSize(Old);
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);
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
assert(!AFI->isThumb1OnlyFunction() &&
"This eliminateCallFramePseudoInstr does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
// Replace the pseudo instruction with a new instruction...
unsigned Opc = Old.getOpcode();
int PIdx = Old.findFirstPredOperandIdx();
ARMCC::CondCodes Pred =
(PIdx == -1) ? ARMCC::AL
: (ARMCC::CondCodes)Old.getOperand(PIdx).getImm();
unsigned PredReg = TII.getFramePred(Old);
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);
}
}
}
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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