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llvm-project/llvm/lib/Target/X86/X86ExpandPseudo.cpp

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//===------- X86ExpandPseudo.cpp - Expand pseudo instructions -------------===//
//
// 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 a pass that expands pseudo instructions into target
// instructions to allow proper scheduling, if-conversion, other late
// optimizations, or simply the encoding of the instructions.
//
//===----------------------------------------------------------------------===//
#include "X86.h"
#include "X86FrameLowering.h"
#include "X86InstrBuilder.h"
#include "X86InstrInfo.h"
#include "X86MachineFunctionInfo.h"
#include "X86Subtarget.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/Passes.h" // For IDs of passes that are preserved.
#include "llvm/IR/GlobalValue.h"
using namespace llvm;
#define DEBUG_TYPE "x86-pseudo"
#define X86_EXPAND_PSEUDO_NAME "X86 pseudo instruction expansion pass"
namespace {
class X86ExpandPseudo : public MachineFunctionPass {
public:
static char ID;
X86ExpandPseudo() : MachineFunctionPass(ID) {}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
}
const X86Subtarget *STI = nullptr;
const X86InstrInfo *TII = nullptr;
const X86RegisterInfo *TRI = nullptr;
const X86MachineFunctionInfo *X86FI = nullptr;
const X86FrameLowering *X86FL = nullptr;
bool runOnMachineFunction(MachineFunction &Fn) override;
MachineFunctionProperties getRequiredProperties() const override {
return MachineFunctionProperties().set(
MachineFunctionProperties::Property::NoVRegs);
}
StringRef getPassName() const override {
return "X86 pseudo instruction expansion pass";
}
private:
void ExpandICallBranchFunnel(MachineBasicBlock *MBB,
MachineBasicBlock::iterator MBBI);
bool ExpandMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI);
bool ExpandMBB(MachineBasicBlock &MBB);
};
char X86ExpandPseudo::ID = 0;
} // End anonymous namespace.
INITIALIZE_PASS(X86ExpandPseudo, DEBUG_TYPE, X86_EXPAND_PSEUDO_NAME, false,
false)
void X86ExpandPseudo::ExpandICallBranchFunnel(
MachineBasicBlock *MBB, MachineBasicBlock::iterator MBBI) {
MachineBasicBlock *JTMBB = MBB;
MachineInstr *JTInst = &*MBBI;
MachineFunction *MF = MBB->getParent();
const BasicBlock *BB = MBB->getBasicBlock();
auto InsPt = MachineFunction::iterator(MBB);
++InsPt;
std::vector<std::pair<MachineBasicBlock *, unsigned>> TargetMBBs;
DebugLoc DL = JTInst->getDebugLoc();
MachineOperand Selector = JTInst->getOperand(0);
const GlobalValue *CombinedGlobal = JTInst->getOperand(1).getGlobal();
auto CmpTarget = [&](unsigned Target) {
if (Selector.isReg())
MBB->addLiveIn(Selector.getReg());
BuildMI(*MBB, MBBI, DL, TII->get(X86::LEA64r), X86::R11)
.addReg(X86::RIP)
.addImm(1)
.addReg(0)
.addGlobalAddress(CombinedGlobal,
JTInst->getOperand(2 + 2 * Target).getImm())
.addReg(0);
BuildMI(*MBB, MBBI, DL, TII->get(X86::CMP64rr))
.add(Selector)
.addReg(X86::R11);
};
auto CreateMBB = [&]() {
auto *NewMBB = MF->CreateMachineBasicBlock(BB);
MBB->addSuccessor(NewMBB);
if (!MBB->isLiveIn(X86::EFLAGS))
MBB->addLiveIn(X86::EFLAGS);
return NewMBB;
};
auto EmitCondJump = [&](unsigned CC, MachineBasicBlock *ThenMBB) {
BuildMI(*MBB, MBBI, DL, TII->get(X86::JCC_1)).addMBB(ThenMBB).addImm(CC);
auto *ElseMBB = CreateMBB();
MF->insert(InsPt, ElseMBB);
MBB = ElseMBB;
MBBI = MBB->end();
};
auto EmitCondJumpTarget = [&](unsigned CC, unsigned Target) {
auto *ThenMBB = CreateMBB();
TargetMBBs.push_back({ThenMBB, Target});
EmitCondJump(CC, ThenMBB);
};
auto EmitTailCall = [&](unsigned Target) {
BuildMI(*MBB, MBBI, DL, TII->get(X86::TAILJMPd64))
.add(JTInst->getOperand(3 + 2 * Target));
};
std::function<void(unsigned, unsigned)> EmitBranchFunnel =
[&](unsigned FirstTarget, unsigned NumTargets) {
if (NumTargets == 1) {
EmitTailCall(FirstTarget);
return;
}
if (NumTargets == 2) {
CmpTarget(FirstTarget + 1);
EmitCondJumpTarget(X86::COND_B, FirstTarget);
EmitTailCall(FirstTarget + 1);
return;
}
if (NumTargets < 6) {
CmpTarget(FirstTarget + 1);
EmitCondJumpTarget(X86::COND_B, FirstTarget);
EmitCondJumpTarget(X86::COND_E, FirstTarget + 1);
EmitBranchFunnel(FirstTarget + 2, NumTargets - 2);
return;
}
auto *ThenMBB = CreateMBB();
CmpTarget(FirstTarget + (NumTargets / 2));
EmitCondJump(X86::COND_B, ThenMBB);
EmitCondJumpTarget(X86::COND_E, FirstTarget + (NumTargets / 2));
EmitBranchFunnel(FirstTarget + (NumTargets / 2) + 1,
NumTargets - (NumTargets / 2) - 1);
MF->insert(InsPt, ThenMBB);
MBB = ThenMBB;
MBBI = MBB->end();
EmitBranchFunnel(FirstTarget, NumTargets / 2);
};
EmitBranchFunnel(0, (JTInst->getNumOperands() - 2) / 2);
for (auto P : TargetMBBs) {
MF->insert(InsPt, P.first);
BuildMI(P.first, DL, TII->get(X86::TAILJMPd64))
.add(JTInst->getOperand(3 + 2 * P.second));
}
JTMBB->erase(JTInst);
}
/// If \p MBBI is a pseudo instruction, this method expands
/// it to the corresponding (sequence of) actual instruction(s).
/// \returns true if \p MBBI has been expanded.
bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI) {
MachineInstr &MI = *MBBI;
unsigned Opcode = MI.getOpcode();
DebugLoc DL = MBBI->getDebugLoc();
switch (Opcode) {
default:
return false;
case X86::TCRETURNdi:
case X86::TCRETURNdicc:
case X86::TCRETURNri:
case X86::TCRETURNmi:
case X86::TCRETURNdi64:
case X86::TCRETURNdi64cc:
case X86::TCRETURNri64:
case X86::TCRETURNmi64: {
bool isMem = Opcode == X86::TCRETURNmi || Opcode == X86::TCRETURNmi64;
MachineOperand &JumpTarget = MBBI->getOperand(0);
MachineOperand &StackAdjust = MBBI->getOperand(isMem ? X86::AddrNumOperands
: 1);
assert(StackAdjust.isImm() && "Expecting immediate value.");
// Adjust stack pointer.
int StackAdj = StackAdjust.getImm();
int MaxTCDelta = X86FI->getTCReturnAddrDelta();
int Offset = 0;
assert(MaxTCDelta <= 0 && "MaxTCDelta should never be positive");
// Incoporate the retaddr area.
Offset = StackAdj - MaxTCDelta;
assert(Offset >= 0 && "Offset should never be negative");
if (Opcode == X86::TCRETURNdicc || Opcode == X86::TCRETURNdi64cc) {
assert(Offset == 0 && "Conditional tail call cannot adjust the stack.");
}
if (Offset) {
// Check for possible merge with preceding ADD instruction.
Offset += X86FL->mergeSPUpdates(MBB, MBBI, true);
X86FL->emitSPUpdate(MBB, MBBI, DL, Offset, /*InEpilogue=*/true);
}
// Jump to label or value in register.
bool IsWin64 = STI->isTargetWin64();
if (Opcode == X86::TCRETURNdi || Opcode == X86::TCRETURNdicc ||
Opcode == X86::TCRETURNdi64 || Opcode == X86::TCRETURNdi64cc) {
unsigned Op;
switch (Opcode) {
case X86::TCRETURNdi:
Op = X86::TAILJMPd;
break;
case X86::TCRETURNdicc:
Op = X86::TAILJMPd_CC;
break;
case X86::TCRETURNdi64cc:
assert(!MBB.getParent()->hasWinCFI() &&
"Conditional tail calls confuse "
"the Win64 unwinder.");
Op = X86::TAILJMPd64_CC;
break;
default:
// Note: Win64 uses REX prefixes indirect jumps out of functions, but
// not direct ones.
Op = X86::TAILJMPd64;
break;
}
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII->get(Op));
if (JumpTarget.isGlobal()) {
MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
JumpTarget.getTargetFlags());
} else {
assert(JumpTarget.isSymbol());
MIB.addExternalSymbol(JumpTarget.getSymbolName(),
JumpTarget.getTargetFlags());
}
if (Op == X86::TAILJMPd_CC || Op == X86::TAILJMPd64_CC) {
MIB.addImm(MBBI->getOperand(2).getImm());
}
} else if (Opcode == X86::TCRETURNmi || Opcode == X86::TCRETURNmi64) {
unsigned Op = (Opcode == X86::TCRETURNmi)
? X86::TAILJMPm
: (IsWin64 ? X86::TAILJMPm64_REX : X86::TAILJMPm64);
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII->get(Op));
for (unsigned i = 0; i != X86::AddrNumOperands; ++i)
MIB.add(MBBI->getOperand(i));
} else if (Opcode == X86::TCRETURNri64) {
JumpTarget.setIsKill();
BuildMI(MBB, MBBI, DL,
TII->get(IsWin64 ? X86::TAILJMPr64_REX : X86::TAILJMPr64))
.add(JumpTarget);
} else {
JumpTarget.setIsKill();
BuildMI(MBB, MBBI, DL, TII->get(X86::TAILJMPr))
.add(JumpTarget);
}
MachineInstr &NewMI = *std::prev(MBBI);
NewMI.copyImplicitOps(*MBBI->getParent()->getParent(), *MBBI);
MBB.getParent()->moveCallSiteInfo(&*MBBI, &NewMI);
// Delete the pseudo instruction TCRETURN.
MBB.erase(MBBI);
return true;
}
case X86::EH_RETURN:
case X86::EH_RETURN64: {
MachineOperand &DestAddr = MBBI->getOperand(0);
assert(DestAddr.isReg() && "Offset should be in register!");
const bool Uses64BitFramePtr =
STI->isTarget64BitLP64() || STI->isTargetNaCl64();
Register StackPtr = TRI->getStackRegister();
BuildMI(MBB, MBBI, DL,
TII->get(Uses64BitFramePtr ? X86::MOV64rr : X86::MOV32rr), StackPtr)
.addReg(DestAddr.getReg());
// The EH_RETURN pseudo is really removed during the MC Lowering.
return true;
}
case X86::IRET: {
// Adjust stack to erase error code
int64_t StackAdj = MBBI->getOperand(0).getImm();
X86FL->emitSPUpdate(MBB, MBBI, DL, StackAdj, true);
// Replace pseudo with machine iret
BuildMI(MBB, MBBI, DL,
TII->get(STI->is64Bit() ? X86::IRET64 : X86::IRET32));
MBB.erase(MBBI);
return true;
}
case X86::RET: {
// Adjust stack to erase error code
int64_t StackAdj = MBBI->getOperand(0).getImm();
MachineInstrBuilder MIB;
if (StackAdj == 0) {
MIB = BuildMI(MBB, MBBI, DL,
TII->get(STI->is64Bit() ? X86::RETQ : X86::RETL));
} else if (isUInt<16>(StackAdj)) {
MIB = BuildMI(MBB, MBBI, DL,
TII->get(STI->is64Bit() ? X86::RETIQ : X86::RETIL))
.addImm(StackAdj);
} else {
assert(!STI->is64Bit() &&
"shouldn't need to do this for x86_64 targets!");
// A ret can only handle immediates as big as 2**16-1. If we need to pop
// off bytes before the return address, we must do it manually.
BuildMI(MBB, MBBI, DL, TII->get(X86::POP32r)).addReg(X86::ECX, RegState::Define);
X86FL->emitSPUpdate(MBB, MBBI, DL, StackAdj, /*InEpilogue=*/true);
BuildMI(MBB, MBBI, DL, TII->get(X86::PUSH32r)).addReg(X86::ECX);
MIB = BuildMI(MBB, MBBI, DL, TII->get(X86::RETL));
}
for (unsigned I = 1, E = MBBI->getNumOperands(); I != E; ++I)
MIB.add(MBBI->getOperand(I));
MBB.erase(MBBI);
return true;
}
case X86::EH_RESTORE: {
// Restore ESP and EBP, and optionally ESI if required.
bool IsSEH = isAsynchronousEHPersonality(classifyEHPersonality(
MBB.getParent()->getFunction().getPersonalityFn()));
X86FL->restoreWin32EHStackPointers(MBB, MBBI, DL, /*RestoreSP=*/IsSEH);
MBBI->eraseFromParent();
return true;
}
case X86::LCMPXCHG8B_SAVE_EBX:
case X86::LCMPXCHG16B_SAVE_RBX: {
// Perform the following transformation.
// SaveRbx = pseudocmpxchg Addr, <4 opds for the address>, InArg, SaveRbx
// =>
// [E|R]BX = InArg
// actualcmpxchg Addr
// [E|R]BX = SaveRbx
const MachineOperand &InArg = MBBI->getOperand(6);
Register SaveRbx = MBBI->getOperand(7).getReg();
unsigned ActualInArg =
Opcode == X86::LCMPXCHG8B_SAVE_EBX ? X86::EBX : X86::RBX;
// Copy the input argument of the pseudo into the argument of the
// actual instruction.
TII->copyPhysReg(MBB, MBBI, DL, ActualInArg, InArg.getReg(),
InArg.isKill());
// Create the actual instruction.
unsigned ActualOpc =
Opcode == X86::LCMPXCHG8B_SAVE_EBX ? X86::LCMPXCHG8B : X86::LCMPXCHG16B;
MachineInstr *NewInstr = BuildMI(MBB, MBBI, DL, TII->get(ActualOpc));
// Copy the operands related to the address.
for (unsigned Idx = 1; Idx < 6; ++Idx)
NewInstr->addOperand(MBBI->getOperand(Idx));
// Finally, restore the value of RBX.
TII->copyPhysReg(MBB, MBBI, DL, ActualInArg, SaveRbx,
/*SrcIsKill*/ true);
// Delete the pseudo.
MBBI->eraseFromParent();
return true;
}
case TargetOpcode::ICALL_BRANCH_FUNNEL:
ExpandICallBranchFunnel(&MBB, MBBI);
return true;
}
llvm_unreachable("Previous switch has a fallthrough?");
}
/// Expand all pseudo instructions contained in \p MBB.
/// \returns true if any expansion occurred for \p MBB.
bool X86ExpandPseudo::ExpandMBB(MachineBasicBlock &MBB) {
bool Modified = false;
// MBBI may be invalidated by the expansion.
MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
while (MBBI != E) {
MachineBasicBlock::iterator NMBBI = std::next(MBBI);
Modified |= ExpandMI(MBB, MBBI);
MBBI = NMBBI;
}
return Modified;
}
bool X86ExpandPseudo::runOnMachineFunction(MachineFunction &MF) {
STI = &static_cast<const X86Subtarget &>(MF.getSubtarget());
TII = STI->getInstrInfo();
TRI = STI->getRegisterInfo();
X86FI = MF.getInfo<X86MachineFunctionInfo>();
X86FL = STI->getFrameLowering();
bool Modified = false;
for (MachineBasicBlock &MBB : MF)
Modified |= ExpandMBB(MBB);
return Modified;
}
/// Returns an instance of the pseudo instruction expansion pass.
FunctionPass *llvm::createX86ExpandPseudoPass() {
return new X86ExpandPseudo();
}
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