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llvm-mirror/lib/CodeGen/TargetInstrInfo.cpp
Richard Trieu 7948d10d88 Fix unused variable warning in non-debug builds. 
llvm-svn: 248754
2015-09-28 22:54:43 +00:00

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//===-- TargetInstrInfo.cpp - Target Instruction Information --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/CodeGen/ScoreboardHazardRecognizer.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/CodeGen/TargetSchedule.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include <cctype>
using namespace llvm;
static cl::opt<bool> DisableHazardRecognizer(
"disable-sched-hazard", cl::Hidden, cl::init(false),
cl::desc("Disable hazard detection during preRA scheduling"));
TargetInstrInfo::~TargetInstrInfo() {
}
const TargetRegisterClass*
TargetInstrInfo::getRegClass(const MCInstrDesc &MCID, unsigned OpNum,
const TargetRegisterInfo *TRI,
const MachineFunction &MF) const {
if (OpNum >= MCID.getNumOperands())
return nullptr;
short RegClass = MCID.OpInfo[OpNum].RegClass;
if (MCID.OpInfo[OpNum].isLookupPtrRegClass())
return TRI->getPointerRegClass(MF, RegClass);
// Instructions like INSERT_SUBREG do not have fixed register classes.
if (RegClass < 0)
return nullptr;
// Otherwise just look it up normally.
return TRI->getRegClass(RegClass);
}
/// insertNoop - Insert a noop into the instruction stream at the specified
/// point.
void TargetInstrInfo::insertNoop(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI) const {
llvm_unreachable("Target didn't implement insertNoop!");
}
/// Measure the specified inline asm to determine an approximation of its
/// length.
/// Comments (which run till the next SeparatorString or newline) do not
/// count as an instruction.
/// Any other non-whitespace text is considered an instruction, with
/// multiple instructions separated by SeparatorString or newlines.
/// Variable-length instructions are not handled here; this function
/// may be overloaded in the target code to do that.
unsigned TargetInstrInfo::getInlineAsmLength(const char *Str,
const MCAsmInfo &MAI) const {
// Count the number of instructions in the asm.
bool atInsnStart = true;
unsigned Length = 0;
for (; *Str; ++Str) {
if (*Str == '\n' || strncmp(Str, MAI.getSeparatorString(),
strlen(MAI.getSeparatorString())) == 0)
atInsnStart = true;
if (atInsnStart && !std::isspace(static_cast<unsigned char>(*Str))) {
Length += MAI.getMaxInstLength();
atInsnStart = false;
}
if (atInsnStart && strncmp(Str, MAI.getCommentString(),
strlen(MAI.getCommentString())) == 0)
atInsnStart = false;
}
return Length;
}
/// ReplaceTailWithBranchTo - Delete the instruction OldInst and everything
/// after it, replacing it with an unconditional branch to NewDest.
void
TargetInstrInfo::ReplaceTailWithBranchTo(MachineBasicBlock::iterator Tail,
MachineBasicBlock *NewDest) const {
MachineBasicBlock *MBB = Tail->getParent();
// Remove all the old successors of MBB from the CFG.
while (!MBB->succ_empty())
MBB->removeSuccessor(MBB->succ_begin());
// Remove all the dead instructions from the end of MBB.
MBB->erase(Tail, MBB->end());
// If MBB isn't immediately before MBB, insert a branch to it.
if (++MachineFunction::iterator(MBB) != MachineFunction::iterator(NewDest))
InsertBranch(*MBB, NewDest, nullptr, SmallVector<MachineOperand, 0>(),
Tail->getDebugLoc());
MBB->addSuccessor(NewDest);
}
MachineInstr *TargetInstrInfo::commuteInstructionImpl(MachineInstr *MI,
bool NewMI,
unsigned Idx1,
unsigned Idx2) const {
const MCInstrDesc &MCID = MI->getDesc();
bool HasDef = MCID.getNumDefs();
if (HasDef && !MI->getOperand(0).isReg())
// No idea how to commute this instruction. Target should implement its own.
return nullptr;
unsigned CommutableOpIdx1 = Idx1; (void)CommutableOpIdx1;
unsigned CommutableOpIdx2 = Idx2; (void)CommutableOpIdx2;
assert(findCommutedOpIndices(MI, CommutableOpIdx1, CommutableOpIdx2) &&
CommutableOpIdx1 == Idx1 && CommutableOpIdx2 == Idx2 &&
"TargetInstrInfo::CommuteInstructionImpl(): not commutable operands.");
assert(MI->getOperand(Idx1).isReg() && MI->getOperand(Idx2).isReg() &&
"This only knows how to commute register operands so far");
unsigned Reg0 = HasDef ? MI->getOperand(0).getReg() : 0;
unsigned Reg1 = MI->getOperand(Idx1).getReg();
unsigned Reg2 = MI->getOperand(Idx2).getReg();
unsigned SubReg0 = HasDef ? MI->getOperand(0).getSubReg() : 0;
unsigned SubReg1 = MI->getOperand(Idx1).getSubReg();
unsigned SubReg2 = MI->getOperand(Idx2).getSubReg();
bool Reg1IsKill = MI->getOperand(Idx1).isKill();
bool Reg2IsKill = MI->getOperand(Idx2).isKill();
bool Reg1IsUndef = MI->getOperand(Idx1).isUndef();
bool Reg2IsUndef = MI->getOperand(Idx2).isUndef();
bool Reg1IsInternal = MI->getOperand(Idx1).isInternalRead();
bool Reg2IsInternal = MI->getOperand(Idx2).isInternalRead();
// If destination is tied to either of the commuted source register, then
// it must be updated.
if (HasDef && Reg0 == Reg1 &&
MI->getDesc().getOperandConstraint(Idx1, MCOI::TIED_TO) == 0) {
Reg2IsKill = false;
Reg0 = Reg2;
SubReg0 = SubReg2;
} else if (HasDef && Reg0 == Reg2 &&
MI->getDesc().getOperandConstraint(Idx2, MCOI::TIED_TO) == 0) {
Reg1IsKill = false;
Reg0 = Reg1;
SubReg0 = SubReg1;
}
if (NewMI) {
// Create a new instruction.
MachineFunction &MF = *MI->getParent()->getParent();
MI = MF.CloneMachineInstr(MI);
}
if (HasDef) {
MI->getOperand(0).setReg(Reg0);
MI->getOperand(0).setSubReg(SubReg0);
}
MI->getOperand(Idx2).setReg(Reg1);
MI->getOperand(Idx1).setReg(Reg2);
MI->getOperand(Idx2).setSubReg(SubReg1);
MI->getOperand(Idx1).setSubReg(SubReg2);
MI->getOperand(Idx2).setIsKill(Reg1IsKill);
MI->getOperand(Idx1).setIsKill(Reg2IsKill);
MI->getOperand(Idx2).setIsUndef(Reg1IsUndef);
MI->getOperand(Idx1).setIsUndef(Reg2IsUndef);
MI->getOperand(Idx2).setIsInternalRead(Reg1IsInternal);
MI->getOperand(Idx1).setIsInternalRead(Reg2IsInternal);
return MI;
}
MachineInstr *TargetInstrInfo::commuteInstruction(MachineInstr *MI,
bool NewMI,
unsigned OpIdx1,
unsigned OpIdx2) const {
// If OpIdx1 or OpIdx2 is not specified, then this method is free to choose
// any commutable operand, which is done in findCommutedOpIndices() method
// called below.
if ((OpIdx1 == CommuteAnyOperandIndex || OpIdx2 == CommuteAnyOperandIndex) &&
!findCommutedOpIndices(MI, OpIdx1, OpIdx2)) {
assert(MI->isCommutable() &&
"Precondition violation: MI must be commutable.");
return nullptr;
}
return commuteInstructionImpl(MI, NewMI, OpIdx1, OpIdx2);
}
bool TargetInstrInfo::fixCommutedOpIndices(unsigned &ResultIdx1,
unsigned &ResultIdx2,
unsigned CommutableOpIdx1,
unsigned CommutableOpIdx2) {
if (ResultIdx1 == CommuteAnyOperandIndex &&
ResultIdx2 == CommuteAnyOperandIndex) {
ResultIdx1 = CommutableOpIdx1;
ResultIdx2 = CommutableOpIdx2;
} else if (ResultIdx1 == CommuteAnyOperandIndex) {
if (ResultIdx2 == CommutableOpIdx1)
ResultIdx1 = CommutableOpIdx2;
else if (ResultIdx2 == CommutableOpIdx2)
ResultIdx1 = CommutableOpIdx1;
else
return false;
} else if (ResultIdx2 == CommuteAnyOperandIndex) {
if (ResultIdx1 == CommutableOpIdx1)
ResultIdx2 = CommutableOpIdx2;
else if (ResultIdx1 == CommutableOpIdx2)
ResultIdx2 = CommutableOpIdx1;
else
return false;
} else
// Check that the result operand indices match the given commutable
// operand indices.
return (ResultIdx1 == CommutableOpIdx1 && ResultIdx2 == CommutableOpIdx2) ||
(ResultIdx1 == CommutableOpIdx2 && ResultIdx2 == CommutableOpIdx1);
return true;
}
bool TargetInstrInfo::findCommutedOpIndices(MachineInstr *MI,
unsigned &SrcOpIdx1,
unsigned &SrcOpIdx2) const {
assert(!MI->isBundle() &&
"TargetInstrInfo::findCommutedOpIndices() can't handle bundles");
const MCInstrDesc &MCID = MI->getDesc();
if (!MCID.isCommutable())
return false;
// This assumes v0 = op v1, v2 and commuting would swap v1 and v2. If this
// is not true, then the target must implement this.
unsigned CommutableOpIdx1 = MCID.getNumDefs();
unsigned CommutableOpIdx2 = CommutableOpIdx1 + 1;
if (!fixCommutedOpIndices(SrcOpIdx1, SrcOpIdx2,
CommutableOpIdx1, CommutableOpIdx2))
return false;
if (!MI->getOperand(SrcOpIdx1).isReg() ||
!MI->getOperand(SrcOpIdx2).isReg())
// No idea.
return false;
return true;
}
bool
TargetInstrInfo::isUnpredicatedTerminator(const MachineInstr *MI) const {
if (!MI->isTerminator()) return false;
// Conditional branch is a special case.
if (MI->isBranch() && !MI->isBarrier())
return true;
if (!MI->isPredicable())
return true;
return !isPredicated(MI);
}
bool TargetInstrInfo::PredicateInstruction(
MachineInstr *MI, ArrayRef<MachineOperand> Pred) const {
bool MadeChange = false;
assert(!MI->isBundle() &&
"TargetInstrInfo::PredicateInstruction() can't handle bundles");
const MCInstrDesc &MCID = MI->getDesc();
if (!MI->isPredicable())
return false;
for (unsigned j = 0, i = 0, e = MI->getNumOperands(); i != e; ++i) {
if (MCID.OpInfo[i].isPredicate()) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isReg()) {
MO.setReg(Pred[j].getReg());
MadeChange = true;
} else if (MO.isImm()) {
MO.setImm(Pred[j].getImm());
MadeChange = true;
} else if (MO.isMBB()) {
MO.setMBB(Pred[j].getMBB());
MadeChange = true;
}
++j;
}
}
return MadeChange;
}
bool TargetInstrInfo::hasLoadFromStackSlot(const MachineInstr *MI,
const MachineMemOperand *&MMO,
int &FrameIndex) const {
for (MachineInstr::mmo_iterator o = MI->memoperands_begin(),
oe = MI->memoperands_end();
o != oe;
++o) {
if ((*o)->isLoad()) {
if (const FixedStackPseudoSourceValue *Value =
dyn_cast_or_null<FixedStackPseudoSourceValue>(
(*o)->getPseudoValue())) {
FrameIndex = Value->getFrameIndex();
MMO = *o;
return true;
}
}
}
return false;
}
bool TargetInstrInfo::hasStoreToStackSlot(const MachineInstr *MI,
const MachineMemOperand *&MMO,
int &FrameIndex) const {
for (MachineInstr::mmo_iterator o = MI->memoperands_begin(),
oe = MI->memoperands_end();
o != oe;
++o) {
if ((*o)->isStore()) {
if (const FixedStackPseudoSourceValue *Value =
dyn_cast_or_null<FixedStackPseudoSourceValue>(
(*o)->getPseudoValue())) {
FrameIndex = Value->getFrameIndex();
MMO = *o;
return true;
}
}
}
return false;
}
bool TargetInstrInfo::getStackSlotRange(const TargetRegisterClass *RC,
unsigned SubIdx, unsigned &Size,
unsigned &Offset,
const MachineFunction &MF) const {
if (!SubIdx) {
Size = RC->getSize();
Offset = 0;
return true;
}
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
unsigned BitSize = TRI->getSubRegIdxSize(SubIdx);
// Convert bit size to byte size to be consistent with
// MCRegisterClass::getSize().
if (BitSize % 8)
return false;
int BitOffset = TRI->getSubRegIdxOffset(SubIdx);
if (BitOffset < 0 || BitOffset % 8)
return false;
Size = BitSize /= 8;
Offset = (unsigned)BitOffset / 8;
assert(RC->getSize() >= (Offset + Size) && "bad subregister range");
if (!MF.getDataLayout().isLittleEndian()) {
Offset = RC->getSize() - (Offset + Size);
}
return true;
}
void TargetInstrInfo::reMaterialize(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
unsigned DestReg,
unsigned SubIdx,
const MachineInstr *Orig,
const TargetRegisterInfo &TRI) const {
MachineInstr *MI = MBB.getParent()->CloneMachineInstr(Orig);
MI->substituteRegister(MI->getOperand(0).getReg(), DestReg, SubIdx, TRI);
MBB.insert(I, MI);
}
bool
TargetInstrInfo::produceSameValue(const MachineInstr *MI0,
const MachineInstr *MI1,
const MachineRegisterInfo *MRI) const {
return MI0->isIdenticalTo(MI1, MachineInstr::IgnoreVRegDefs);
}
MachineInstr *TargetInstrInfo::duplicate(MachineInstr *Orig,
MachineFunction &MF) const {
assert(!Orig->isNotDuplicable() &&
"Instruction cannot be duplicated");
return MF.CloneMachineInstr(Orig);
}
// If the COPY instruction in MI can be folded to a stack operation, return
// the register class to use.
static const TargetRegisterClass *canFoldCopy(const MachineInstr *MI,
unsigned FoldIdx) {
assert(MI->isCopy() && "MI must be a COPY instruction");
if (MI->getNumOperands() != 2)
return nullptr;
assert(FoldIdx<2 && "FoldIdx refers no nonexistent operand");
const MachineOperand &FoldOp = MI->getOperand(FoldIdx);
const MachineOperand &LiveOp = MI->getOperand(1-FoldIdx);
if (FoldOp.getSubReg() || LiveOp.getSubReg())
return nullptr;
unsigned FoldReg = FoldOp.getReg();
unsigned LiveReg = LiveOp.getReg();
assert(TargetRegisterInfo::isVirtualRegister(FoldReg) &&
"Cannot fold physregs");
const MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo();
const TargetRegisterClass *RC = MRI.getRegClass(FoldReg);
if (TargetRegisterInfo::isPhysicalRegister(LiveOp.getReg()))
return RC->contains(LiveOp.getReg()) ? RC : nullptr;
if (RC->hasSubClassEq(MRI.getRegClass(LiveReg)))
return RC;
// FIXME: Allow folding when register classes are memory compatible.
return nullptr;
}
void TargetInstrInfo::getNoopForMachoTarget(MCInst &NopInst) const {
llvm_unreachable("Not a MachO target");
}
static MachineInstr *foldPatchpoint(MachineFunction &MF, MachineInstr *MI,
ArrayRef<unsigned> Ops, int FrameIndex,
const TargetInstrInfo &TII) {
unsigned StartIdx = 0;
switch (MI->getOpcode()) {
case TargetOpcode::STACKMAP:
StartIdx = 2; // Skip ID, nShadowBytes.
break;
case TargetOpcode::PATCHPOINT: {
// For PatchPoint, the call args are not foldable.
PatchPointOpers opers(MI);
StartIdx = opers.getVarIdx();
break;
}
default:
llvm_unreachable("unexpected stackmap opcode");
}
// Return false if any operands requested for folding are not foldable (not
// part of the stackmap's live values).
for (unsigned Op : Ops) {
if (Op < StartIdx)
return nullptr;
}
MachineInstr *NewMI =
MF.CreateMachineInstr(TII.get(MI->getOpcode()), MI->getDebugLoc(), true);
MachineInstrBuilder MIB(MF, NewMI);
// No need to fold return, the meta data, and function arguments
for (unsigned i = 0; i < StartIdx; ++i)
MIB.addOperand(MI->getOperand(i));
for (unsigned i = StartIdx; i < MI->getNumOperands(); ++i) {
MachineOperand &MO = MI->getOperand(i);
if (std::find(Ops.begin(), Ops.end(), i) != Ops.end()) {
unsigned SpillSize;
unsigned SpillOffset;
// Compute the spill slot size and offset.
const TargetRegisterClass *RC =
MF.getRegInfo().getRegClass(MO.getReg());
bool Valid =
TII.getStackSlotRange(RC, MO.getSubReg(), SpillSize, SpillOffset, MF);
if (!Valid)
report_fatal_error("cannot spill patchpoint subregister operand");
MIB.addImm(StackMaps::IndirectMemRefOp);
MIB.addImm(SpillSize);
MIB.addFrameIndex(FrameIndex);
MIB.addImm(SpillOffset);
}
else
MIB.addOperand(MO);
}
return NewMI;
}
/// foldMemoryOperand - Attempt to fold a load or store of the specified stack
/// slot into the specified machine instruction for the specified operand(s).
/// If this is possible, a new instruction is returned with the specified
/// operand folded, otherwise NULL is returned. The client is responsible for
/// removing the old instruction and adding the new one in the instruction
/// stream.
MachineInstr *TargetInstrInfo::foldMemoryOperand(MachineBasicBlock::iterator MI,
ArrayRef<unsigned> Ops,
int FI) const {
unsigned Flags = 0;
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
if (MI->getOperand(Ops[i]).isDef())
Flags |= MachineMemOperand::MOStore;
else
Flags |= MachineMemOperand::MOLoad;
MachineBasicBlock *MBB = MI->getParent();
assert(MBB && "foldMemoryOperand needs an inserted instruction");
MachineFunction &MF = *MBB->getParent();
MachineInstr *NewMI = nullptr;
if (MI->getOpcode() == TargetOpcode::STACKMAP ||
MI->getOpcode() == TargetOpcode::PATCHPOINT) {
// Fold stackmap/patchpoint.
NewMI = foldPatchpoint(MF, MI, Ops, FI, *this);
if (NewMI)
MBB->insert(MI, NewMI);
} else {
// Ask the target to do the actual folding.
NewMI = foldMemoryOperandImpl(MF, MI, Ops, MI, FI);
}
if (NewMI) {
NewMI->setMemRefs(MI->memoperands_begin(), MI->memoperands_end());
// Add a memory operand, foldMemoryOperandImpl doesn't do that.
assert((!(Flags & MachineMemOperand::MOStore) ||
NewMI->mayStore()) &&
"Folded a def to a non-store!");
assert((!(Flags & MachineMemOperand::MOLoad) ||
NewMI->mayLoad()) &&
"Folded a use to a non-load!");
const MachineFrameInfo &MFI = *MF.getFrameInfo();
assert(MFI.getObjectOffset(FI) != -1);
MachineMemOperand *MMO = MF.getMachineMemOperand(
MachinePointerInfo::getFixedStack(MF, FI), Flags, MFI.getObjectSize(FI),
MFI.getObjectAlignment(FI));
NewMI->addMemOperand(MF, MMO);
return NewMI;
}
// Straight COPY may fold as load/store.
if (!MI->isCopy() || Ops.size() != 1)
return nullptr;
const TargetRegisterClass *RC = canFoldCopy(MI, Ops[0]);
if (!RC)
return nullptr;
const MachineOperand &MO = MI->getOperand(1-Ops[0]);
MachineBasicBlock::iterator Pos = MI;
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
if (Flags == MachineMemOperand::MOStore)
storeRegToStackSlot(*MBB, Pos, MO.getReg(), MO.isKill(), FI, RC, TRI);
else
loadRegFromStackSlot(*MBB, Pos, MO.getReg(), FI, RC, TRI);
return --Pos;
}
bool TargetInstrInfo::hasReassociableOperands(
const MachineInstr &Inst, const MachineBasicBlock *MBB) const {
const MachineOperand &Op1 = Inst.getOperand(1);
const MachineOperand &Op2 = Inst.getOperand(2);
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
// We need virtual register definitions for the operands that we will
// reassociate.
MachineInstr *MI1 = nullptr;
MachineInstr *MI2 = nullptr;
if (Op1.isReg() && TargetRegisterInfo::isVirtualRegister(Op1.getReg()))
MI1 = MRI.getUniqueVRegDef(Op1.getReg());
if (Op2.isReg() && TargetRegisterInfo::isVirtualRegister(Op2.getReg()))
MI2 = MRI.getUniqueVRegDef(Op2.getReg());
// And they need to be in the trace (otherwise, they won't have a depth).
if (MI1 && MI2 && MI1->getParent() == MBB && MI2->getParent() == MBB)
return true;
return false;
}
bool TargetInstrInfo::hasReassociableSibling(const MachineInstr &Inst,
bool &Commuted) const {
const MachineBasicBlock *MBB = Inst.getParent();
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
MachineInstr *MI1 = MRI.getUniqueVRegDef(Inst.getOperand(1).getReg());
MachineInstr *MI2 = MRI.getUniqueVRegDef(Inst.getOperand(2).getReg());
unsigned AssocOpcode = Inst.getOpcode();
// If only one operand has the same opcode and it's the second source operand,
// the operands must be commuted.
Commuted = MI1->getOpcode() != AssocOpcode && MI2->getOpcode() == AssocOpcode;
if (Commuted)
std::swap(MI1, MI2);
// 1. The previous instruction must be the same type as Inst.
// 2. The previous instruction must have virtual register definitions for its
// operands in the same basic block as Inst.
// 3. The previous instruction's result must only be used by Inst.
if (MI1->getOpcode() == AssocOpcode && hasReassociableOperands(*MI1, MBB) &&
MRI.hasOneNonDBGUse(MI1->getOperand(0).getReg()))
return true;
return false;
}
// 1. The operation must be associative and commutative.
// 2. The instruction must have virtual register definitions for its
// operands in the same basic block.
// 3. The instruction must have a reassociable sibling.
bool TargetInstrInfo::isReassociationCandidate(const MachineInstr &Inst,
bool &Commuted) const {
if (isAssociativeAndCommutative(Inst) &&
hasReassociableOperands(Inst, Inst.getParent()) &&
hasReassociableSibling(Inst, Commuted))
return true;
return false;
}
// The concept of the reassociation pass is that these operations can benefit
// from this kind of transformation:
//
// A = ? op ?
// B = A op X (Prev)
// C = B op Y (Root)
// -->
// A = ? op ?
// B = X op Y
// C = A op B
//
// breaking the dependency between A and B, allowing them to be executed in
// parallel (or back-to-back in a pipeline) instead of depending on each other.
// FIXME: This has the potential to be expensive (compile time) while not
// improving the code at all. Some ways to limit the overhead:
// 1. Track successful transforms; bail out if hit rate gets too low.
// 2. Only enable at -O3 or some other non-default optimization level.
// 3. Pre-screen pattern candidates here: if an operand of the previous
// instruction is known to not increase the critical path, then don't match
// that pattern.
bool TargetInstrInfo::getMachineCombinerPatterns(
MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Patterns) const {
bool Commute;
if (isReassociationCandidate(Root, Commute)) {
// We found a sequence of instructions that may be suitable for a
// reassociation of operands to increase ILP. Specify each commutation
// possibility for the Prev instruction in the sequence and let the
// machine combiner decide if changing the operands is worthwhile.
if (Commute) {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_YB);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_YB);
} else {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_BY);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_BY);
}
return true;
}
return false;
}
/// Attempt the reassociation transformation to reduce critical path length.
/// See the above comments before getMachineCombinerPatterns().
void TargetInstrInfo::reassociateOps(
MachineInstr &Root, MachineInstr &Prev,
MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const {
MachineFunction *MF = Root.getParent()->getParent();
MachineRegisterInfo &MRI = MF->getRegInfo();
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
const TargetRegisterClass *RC = Root.getRegClassConstraint(0, TII, TRI);
// This array encodes the operand index for each parameter because the
// operands may be commuted. Each row corresponds to a pattern value,
// and each column specifies the index of A, B, X, Y.
unsigned OpIdx[4][4] = {
{ 1, 1, 2, 2 },
{ 1, 2, 2, 1 },
{ 2, 1, 1, 2 },
{ 2, 2, 1, 1 }
};
MachineOperand &OpA = Prev.getOperand(OpIdx[Pattern][0]);
MachineOperand &OpB = Root.getOperand(OpIdx[Pattern][1]);
MachineOperand &OpX = Prev.getOperand(OpIdx[Pattern][2]);
MachineOperand &OpY = Root.getOperand(OpIdx[Pattern][3]);
MachineOperand &OpC = Root.getOperand(0);
unsigned RegA = OpA.getReg();
unsigned RegB = OpB.getReg();
unsigned RegX = OpX.getReg();
unsigned RegY = OpY.getReg();
unsigned RegC = OpC.getReg();
if (TargetRegisterInfo::isVirtualRegister(RegA))
MRI.constrainRegClass(RegA, RC);
if (TargetRegisterInfo::isVirtualRegister(RegB))
MRI.constrainRegClass(RegB, RC);
if (TargetRegisterInfo::isVirtualRegister(RegX))
MRI.constrainRegClass(RegX, RC);
if (TargetRegisterInfo::isVirtualRegister(RegY))
MRI.constrainRegClass(RegY, RC);
if (TargetRegisterInfo::isVirtualRegister(RegC))
MRI.constrainRegClass(RegC, RC);
// Create a new virtual register for the result of (X op Y) instead of
// recycling RegB because the MachineCombiner's computation of the critical
// path requires a new register definition rather than an existing one.
unsigned NewVR = MRI.createVirtualRegister(RC);
InstrIdxForVirtReg.insert(std::make_pair(NewVR, 0));
unsigned Opcode = Root.getOpcode();
bool KillA = OpA.isKill();
bool KillX = OpX.isKill();
bool KillY = OpY.isKill();
// Create new instructions for insertion.
MachineInstrBuilder MIB1 =
BuildMI(*MF, Prev.getDebugLoc(), TII->get(Opcode), NewVR)
.addReg(RegX, getKillRegState(KillX))
.addReg(RegY, getKillRegState(KillY));
MachineInstrBuilder MIB2 =
BuildMI(*MF, Root.getDebugLoc(), TII->get(Opcode), RegC)
.addReg(RegA, getKillRegState(KillA))
.addReg(NewVR, getKillRegState(true));
setSpecialOperandAttr(Root, Prev, *MIB1, *MIB2);
// Record new instructions for insertion and old instructions for deletion.
InsInstrs.push_back(MIB1);
InsInstrs.push_back(MIB2);
DelInstrs.push_back(&Prev);
DelInstrs.push_back(&Root);
}
void TargetInstrInfo::genAlternativeCodeSequence(
MachineInstr &Root, MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstIdxForVirtReg) const {
MachineRegisterInfo &MRI = Root.getParent()->getParent()->getRegInfo();
// Select the previous instruction in the sequence based on the input pattern.
MachineInstr *Prev = nullptr;
switch (Pattern) {
case MachineCombinerPattern::MC_REASSOC_AX_BY:
case MachineCombinerPattern::MC_REASSOC_XA_BY:
Prev = MRI.getUniqueVRegDef(Root.getOperand(1).getReg());
break;
case MachineCombinerPattern::MC_REASSOC_AX_YB:
case MachineCombinerPattern::MC_REASSOC_XA_YB:
Prev = MRI.getUniqueVRegDef(Root.getOperand(2).getReg());
break;
default:
break;
}
assert(Prev && "Unknown pattern for machine combiner");
reassociateOps(Root, *Prev, Pattern, InsInstrs, DelInstrs, InstIdxForVirtReg);
return;
}
/// foldMemoryOperand - Same as the previous version except it allows folding
/// of any load and store from / to any address, not just from a specific
/// stack slot.
MachineInstr *TargetInstrInfo::foldMemoryOperand(MachineBasicBlock::iterator MI,
ArrayRef<unsigned> Ops,
MachineInstr *LoadMI) const {
assert(LoadMI->canFoldAsLoad() && "LoadMI isn't foldable!");
#ifndef NDEBUG
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
assert(MI->getOperand(Ops[i]).isUse() && "Folding load into def!");
#endif
MachineBasicBlock &MBB = *MI->getParent();
MachineFunction &MF = *MBB.getParent();
// Ask the target to do the actual folding.
MachineInstr *NewMI = nullptr;
int FrameIndex = 0;
if ((MI->getOpcode() == TargetOpcode::STACKMAP ||
MI->getOpcode() == TargetOpcode::PATCHPOINT) &&
isLoadFromStackSlot(LoadMI, FrameIndex)) {
// Fold stackmap/patchpoint.
NewMI = foldPatchpoint(MF, MI, Ops, FrameIndex, *this);
if (NewMI)
NewMI = MBB.insert(MI, NewMI);
} else {
// Ask the target to do the actual folding.
NewMI = foldMemoryOperandImpl(MF, MI, Ops, MI, LoadMI);
}
if (!NewMI) return nullptr;
// Copy the memoperands from the load to the folded instruction.
if (MI->memoperands_empty()) {
NewMI->setMemRefs(LoadMI->memoperands_begin(),
LoadMI->memoperands_end());
}
else {
// Handle the rare case of folding multiple loads.
NewMI->setMemRefs(MI->memoperands_begin(),
MI->memoperands_end());
for (MachineInstr::mmo_iterator I = LoadMI->memoperands_begin(),
E = LoadMI->memoperands_end(); I != E; ++I) {
NewMI->addMemOperand(MF, *I);
}
}
return NewMI;
}
bool TargetInstrInfo::
isReallyTriviallyReMaterializableGeneric(const MachineInstr *MI,
AliasAnalysis *AA) const {
const MachineFunction &MF = *MI->getParent()->getParent();
const MachineRegisterInfo &MRI = MF.getRegInfo();
// Remat clients assume operand 0 is the defined register.
if (!MI->getNumOperands() || !MI->getOperand(0).isReg())
return false;
unsigned DefReg = MI->getOperand(0).getReg();
// A sub-register definition can only be rematerialized if the instruction
// doesn't read the other parts of the register. Otherwise it is really a
// read-modify-write operation on the full virtual register which cannot be
// moved safely.
if (TargetRegisterInfo::isVirtualRegister(DefReg) &&
MI->getOperand(0).getSubReg() && MI->readsVirtualRegister(DefReg))
return false;
// A load from a fixed stack slot can be rematerialized. This may be
// redundant with subsequent checks, but it's target-independent,
// simple, and a common case.
int FrameIdx = 0;
if (isLoadFromStackSlot(MI, FrameIdx) &&
MF.getFrameInfo()->isImmutableObjectIndex(FrameIdx))
return true;
// Avoid instructions obviously unsafe for remat.
if (MI->isNotDuplicable() || MI->mayStore() ||
MI->hasUnmodeledSideEffects())
return false;
// Don't remat inline asm. We have no idea how expensive it is
// even if it's side effect free.
if (MI->isInlineAsm())
return false;
// Avoid instructions which load from potentially varying memory.
if (MI->mayLoad() && !MI->isInvariantLoad(AA))
return false;
// If any of the registers accessed are non-constant, conservatively assume
// the instruction is not rematerializable.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
// Check for a well-behaved physical register.
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
if (MO.isUse()) {
// If the physreg has no defs anywhere, it's just an ambient register
// and we can freely move its uses. Alternatively, if it's allocatable,
// it could get allocated to something with a def during allocation.
if (!MRI.isConstantPhysReg(Reg, MF))
return false;
} else {
// A physreg def. We can't remat it.
return false;
}
continue;
}
// Only allow one virtual-register def. There may be multiple defs of the
// same virtual register, though.
if (MO.isDef() && Reg != DefReg)
return false;
// Don't allow any virtual-register uses. Rematting an instruction with
// virtual register uses would length the live ranges of the uses, which
// is not necessarily a good idea, certainly not "trivial".
if (MO.isUse())
return false;
}
// Everything checked out.
return true;
}
int TargetInstrInfo::getSPAdjust(const MachineInstr *MI) const {
const MachineFunction *MF = MI->getParent()->getParent();
const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
bool StackGrowsDown =
TFI->getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
unsigned FrameSetupOpcode = getCallFrameSetupOpcode();
unsigned FrameDestroyOpcode = getCallFrameDestroyOpcode();
if (MI->getOpcode() != FrameSetupOpcode &&
MI->getOpcode() != FrameDestroyOpcode)
return 0;
int SPAdj = MI->getOperand(0).getImm();
SPAdj = TFI->alignSPAdjust(SPAdj);
if ((!StackGrowsDown && MI->getOpcode() == FrameSetupOpcode) ||
(StackGrowsDown && MI->getOpcode() == FrameDestroyOpcode))
SPAdj = -SPAdj;
return SPAdj;
}
/// isSchedulingBoundary - Test if the given instruction should be
/// considered a scheduling boundary. This primarily includes labels
/// and terminators.
bool TargetInstrInfo::isSchedulingBoundary(const MachineInstr *MI,
const MachineBasicBlock *MBB,
const MachineFunction &MF) const {
// Terminators and labels can't be scheduled around.
if (MI->isTerminator() || MI->isPosition())
return true;
// Don't attempt to schedule around any instruction that defines
// a stack-oriented pointer, as it's unlikely to be profitable. This
// saves compile time, because it doesn't require every single
// stack slot reference to depend on the instruction that does the
// modification.
const TargetLowering &TLI = *MF.getSubtarget().getTargetLowering();
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
if (MI->modifiesRegister(TLI.getStackPointerRegisterToSaveRestore(), TRI))
return true;
return false;
}
// Provide a global flag for disabling the PreRA hazard recognizer that targets
// may choose to honor.
bool TargetInstrInfo::usePreRAHazardRecognizer() const {
return !DisableHazardRecognizer;
}
// Default implementation of CreateTargetRAHazardRecognizer.
ScheduleHazardRecognizer *TargetInstrInfo::
CreateTargetHazardRecognizer(const TargetSubtargetInfo *STI,
const ScheduleDAG *DAG) const {
// Dummy hazard recognizer allows all instructions to issue.
return new ScheduleHazardRecognizer();
}
// Default implementation of CreateTargetMIHazardRecognizer.
ScheduleHazardRecognizer *TargetInstrInfo::
CreateTargetMIHazardRecognizer(const InstrItineraryData *II,
const ScheduleDAG *DAG) const {
return (ScheduleHazardRecognizer *)
new ScoreboardHazardRecognizer(II, DAG, "misched");
}
// Default implementation of CreateTargetPostRAHazardRecognizer.
ScheduleHazardRecognizer *TargetInstrInfo::
CreateTargetPostRAHazardRecognizer(const InstrItineraryData *II,
const ScheduleDAG *DAG) const {
return (ScheduleHazardRecognizer *)
new ScoreboardHazardRecognizer(II, DAG, "post-RA-sched");
}
//===----------------------------------------------------------------------===//
// SelectionDAG latency interface.
//===----------------------------------------------------------------------===//
int
TargetInstrInfo::getOperandLatency(const InstrItineraryData *ItinData,
SDNode *DefNode, unsigned DefIdx,
SDNode *UseNode, unsigned UseIdx) const {
if (!ItinData || ItinData->isEmpty())
return -1;
if (!DefNode->isMachineOpcode())
return -1;
unsigned DefClass = get(DefNode->getMachineOpcode()).getSchedClass();
if (!UseNode->isMachineOpcode())
return ItinData->getOperandCycle(DefClass, DefIdx);
unsigned UseClass = get(UseNode->getMachineOpcode()).getSchedClass();
return ItinData->getOperandLatency(DefClass, DefIdx, UseClass, UseIdx);
}
int TargetInstrInfo::getInstrLatency(const InstrItineraryData *ItinData,
SDNode *N) const {
if (!ItinData || ItinData->isEmpty())
return 1;
if (!N->isMachineOpcode())
return 1;
return ItinData->getStageLatency(get(N->getMachineOpcode()).getSchedClass());
}
//===----------------------------------------------------------------------===//
// MachineInstr latency interface.
//===----------------------------------------------------------------------===//
unsigned
TargetInstrInfo::getNumMicroOps(const InstrItineraryData *ItinData,
const MachineInstr *MI) const {
if (!ItinData || ItinData->isEmpty())
return 1;
unsigned Class = MI->getDesc().getSchedClass();
int UOps = ItinData->Itineraries[Class].NumMicroOps;
if (UOps >= 0)
return UOps;
// The # of u-ops is dynamically determined. The specific target should
// override this function to return the right number.
return 1;
}
/// Return the default expected latency for a def based on it's opcode.
unsigned TargetInstrInfo::defaultDefLatency(const MCSchedModel &SchedModel,
const MachineInstr *DefMI) const {
if (DefMI->isTransient())
return 0;
if (DefMI->mayLoad())
return SchedModel.LoadLatency;
if (isHighLatencyDef(DefMI->getOpcode()))
return SchedModel.HighLatency;
return 1;
}
unsigned TargetInstrInfo::getPredicationCost(const MachineInstr *) const {
return 0;
}
unsigned TargetInstrInfo::
getInstrLatency(const InstrItineraryData *ItinData,
const MachineInstr *MI,
unsigned *PredCost) const {
// Default to one cycle for no itinerary. However, an "empty" itinerary may
// still have a MinLatency property, which getStageLatency checks.
if (!ItinData)
return MI->mayLoad() ? 2 : 1;
return ItinData->getStageLatency(MI->getDesc().getSchedClass());
}
bool TargetInstrInfo::hasLowDefLatency(const TargetSchedModel &SchedModel,
const MachineInstr *DefMI,
unsigned DefIdx) const {
const InstrItineraryData *ItinData = SchedModel.getInstrItineraries();
if (!ItinData || ItinData->isEmpty())
return false;
unsigned DefClass = DefMI->getDesc().getSchedClass();
int DefCycle = ItinData->getOperandCycle(DefClass, DefIdx);
return (DefCycle != -1 && DefCycle <= 1);
}
/// Both DefMI and UseMI must be valid. By default, call directly to the
/// itinerary. This may be overriden by the target.
int TargetInstrInfo::
getOperandLatency(const InstrItineraryData *ItinData,
const MachineInstr *DefMI, unsigned DefIdx,
const MachineInstr *UseMI, unsigned UseIdx) const {
unsigned DefClass = DefMI->getDesc().getSchedClass();
unsigned UseClass = UseMI->getDesc().getSchedClass();
return ItinData->getOperandLatency(DefClass, DefIdx, UseClass, UseIdx);
}
/// If we can determine the operand latency from the def only, without itinerary
/// lookup, do so. Otherwise return -1.
int TargetInstrInfo::computeDefOperandLatency(
const InstrItineraryData *ItinData,
const MachineInstr *DefMI) const {
// Let the target hook getInstrLatency handle missing itineraries.
if (!ItinData)
return getInstrLatency(ItinData, DefMI);
if(ItinData->isEmpty())
return defaultDefLatency(ItinData->SchedModel, DefMI);
// ...operand lookup required
return -1;
}
/// computeOperandLatency - Compute and return the latency of the given data
/// dependent def and use when the operand indices are already known. UseMI may
/// be NULL for an unknown use.
///
/// FindMin may be set to get the minimum vs. expected latency. Minimum
/// latency is used for scheduling groups, while expected latency is for
/// instruction cost and critical path.
///
/// Depending on the subtarget's itinerary properties, this may or may not need
/// to call getOperandLatency(). For most subtargets, we don't need DefIdx or
/// UseIdx to compute min latency.
unsigned TargetInstrInfo::
computeOperandLatency(const InstrItineraryData *ItinData,
const MachineInstr *DefMI, unsigned DefIdx,
const MachineInstr *UseMI, unsigned UseIdx) const {
int DefLatency = computeDefOperandLatency(ItinData, DefMI);
if (DefLatency >= 0)
return DefLatency;
assert(ItinData && !ItinData->isEmpty() && "computeDefOperandLatency fail");
int OperLatency = 0;
if (UseMI)
OperLatency = getOperandLatency(ItinData, DefMI, DefIdx, UseMI, UseIdx);
else {
unsigned DefClass = DefMI->getDesc().getSchedClass();
OperLatency = ItinData->getOperandCycle(DefClass, DefIdx);
}
if (OperLatency >= 0)
return OperLatency;
// No operand latency was found.
unsigned InstrLatency = getInstrLatency(ItinData, DefMI);
// Expected latency is the max of the stage latency and itinerary props.
InstrLatency = std::max(InstrLatency,
defaultDefLatency(ItinData->SchedModel, DefMI));
return InstrLatency;
}
bool TargetInstrInfo::getRegSequenceInputs(
const MachineInstr &MI, unsigned DefIdx,
SmallVectorImpl<RegSubRegPairAndIdx> &InputRegs) const {
assert((MI.isRegSequence() ||
MI.isRegSequenceLike()) && "Instruction do not have the proper type");
if (!MI.isRegSequence())
return getRegSequenceLikeInputs(MI, DefIdx, InputRegs);
// We are looking at:
// Def = REG_SEQUENCE v0, sub0, v1, sub1, ...
assert(DefIdx == 0 && "REG_SEQUENCE only has one def");
for (unsigned OpIdx = 1, EndOpIdx = MI.getNumOperands(); OpIdx != EndOpIdx;
OpIdx += 2) {
const MachineOperand &MOReg = MI.getOperand(OpIdx);
const MachineOperand &MOSubIdx = MI.getOperand(OpIdx + 1);
assert(MOSubIdx.isImm() &&
"One of the subindex of the reg_sequence is not an immediate");
// Record Reg:SubReg, SubIdx.
InputRegs.push_back(RegSubRegPairAndIdx(MOReg.getReg(), MOReg.getSubReg(),
(unsigned)MOSubIdx.getImm()));
}
return true;
}
bool TargetInstrInfo::getExtractSubregInputs(
const MachineInstr &MI, unsigned DefIdx,
RegSubRegPairAndIdx &InputReg) const {
assert((MI.isExtractSubreg() ||
MI.isExtractSubregLike()) && "Instruction do not have the proper type");
if (!MI.isExtractSubreg())
return getExtractSubregLikeInputs(MI, DefIdx, InputReg);
// We are looking at:
// Def = EXTRACT_SUBREG v0.sub1, sub0.
assert(DefIdx == 0 && "EXTRACT_SUBREG only has one def");
const MachineOperand &MOReg = MI.getOperand(1);
const MachineOperand &MOSubIdx = MI.getOperand(2);
assert(MOSubIdx.isImm() &&
"The subindex of the extract_subreg is not an immediate");
InputReg.Reg = MOReg.getReg();
InputReg.SubReg = MOReg.getSubReg();
InputReg.SubIdx = (unsigned)MOSubIdx.getImm();
return true;
}
bool TargetInstrInfo::getInsertSubregInputs(
const MachineInstr &MI, unsigned DefIdx,
RegSubRegPair &BaseReg, RegSubRegPairAndIdx &InsertedReg) const {
assert((MI.isInsertSubreg() ||
MI.isInsertSubregLike()) && "Instruction do not have the proper type");
if (!MI.isInsertSubreg())
return getInsertSubregLikeInputs(MI, DefIdx, BaseReg, InsertedReg);
// We are looking at:
// Def = INSERT_SEQUENCE v0, v1, sub0.
assert(DefIdx == 0 && "INSERT_SUBREG only has one def");
const MachineOperand &MOBaseReg = MI.getOperand(1);
const MachineOperand &MOInsertedReg = MI.getOperand(2);
const MachineOperand &MOSubIdx = MI.getOperand(3);
assert(MOSubIdx.isImm() &&
"One of the subindex of the reg_sequence is not an immediate");
BaseReg.Reg = MOBaseReg.getReg();
BaseReg.SubReg = MOBaseReg.getSubReg();
InsertedReg.Reg = MOInsertedReg.getReg();
InsertedReg.SubReg = MOInsertedReg.getSubReg();
InsertedReg.SubIdx = (unsigned)MOSubIdx.getImm();
return true;
}
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