bool X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF,
const CallContext &Context) {
// Ok, we can in fact do the transformation for this call.
// Do not remove the FrameSetup instruction, but adjust the parameters.
// PEI will end up finalizing the handling of this.
MachineBasicBlock::iterator FrameSetup = Context.FrameSetup;
MachineBasicBlock &MBB = *(FrameSetup->getParent());
FrameSetup->getOperand(1).setImm(Context.ExpectedDist);
DebugLoc DL = FrameSetup->getDebugLoc();
// Now, iterate through the vector in reverse order, and replace the movs
// with pushes. MOVmi/MOVmr doesn't have any defs, so no need to
// replace uses.
for (int Idx = (Context.ExpectedDist / 4) - 1; Idx >= 0; --Idx) {
MachineBasicBlock::iterator MOV = *Context.MovVector[Idx];
MachineOperand PushOp = MOV->getOperand(X86::AddrNumOperands);
MachineBasicBlock::iterator Push = nullptr;
if (MOV->getOpcode() == X86::MOV32mi) {
unsigned PushOpcode = X86::PUSHi32;
// If the operand is a small (8-bit) immediate, we can use a
// PUSH instruction with a shorter encoding.
// Note that isImm() may fail even though this is a MOVmi, because
// the operand can also be a symbol.
if (PushOp.isImm()) {
int64_t Val = PushOp.getImm();
if (isInt<8>(Val))
PushOpcode = X86::PUSH32i8;
}
Push = BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode))
.addOperand(PushOp);
} else {
unsigned int Reg = PushOp.getReg();
// If PUSHrmm is not slow on this target, try to fold the source of the
// push into the instruction.
bool SlowPUSHrmm = STI->isAtom() || STI->isSLM();
// Check that this is legal to fold. Right now, we're extremely
// conservative about that.
MachineInstr *DefMov = nullptr;
if (!SlowPUSHrmm && (DefMov = canFoldIntoRegPush(FrameSetup, Reg))) {
Push = BuildMI(MBB, Context.Call, DL, TII->get(X86::PUSH32rmm));
unsigned NumOps = DefMov->getDesc().getNumOperands();
for (unsigned i = NumOps - X86::AddrNumOperands; i != NumOps; ++i)
Push->addOperand(DefMov->getOperand(i));
DefMov->eraseFromParent();
} else {
Push = BuildMI(MBB, Context.Call, DL, TII->get(X86::PUSH32r))
.addReg(Reg)
.getInstr();
}
}
// For debugging, when using SP-based CFA, we need to adjust the CFA
// offset after each push.
// TODO: This is needed only if we require precise CFA.
if (!TFL->hasFP(MF))
TFL->BuildCFI(MBB, std::next(Push), DL,
MCCFIInstruction::createAdjustCfaOffset(nullptr, 4));
MBB.erase(MOV);
}
// The stack-pointer copy is no longer used in the call sequences.
// There should not be any other users, but we can't commit to that, so:
if (MRI->use_empty(Context.SPCopy->getOperand(0).getReg()))
Context.SPCopy->eraseFromParent();
// Once we've done this, we need to make sure PEI doesn't assume a reserved
// frame.
X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
FuncInfo->setHasPushSequences(true);
return true;
}
void X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF,
const CallContext &Context) {
// Ok, we can in fact do the transformation for this call.
// Do not remove the FrameSetup instruction, but adjust the parameters.
// PEI will end up finalizing the handling of this.
MachineBasicBlock::iterator FrameSetup = Context.FrameSetup;
MachineBasicBlock &MBB = *(FrameSetup->getParent());
TII->setFrameAdjustment(*FrameSetup, Context.ExpectedDist);
DebugLoc DL = FrameSetup->getDebugLoc();
bool Is64Bit = STI->is64Bit();
// Now, iterate through the vector in reverse order, and replace the store to
// stack with pushes. MOVmi/MOVmr doesn't have any defs, so no need to
// replace uses.
for (int Idx = (Context.ExpectedDist >> Log2SlotSize) - 1; Idx >= 0; --Idx) {
MachineBasicBlock::iterator Store = *Context.ArgStoreVector[Idx];
MachineOperand PushOp = Store->getOperand(X86::AddrNumOperands);
MachineBasicBlock::iterator Push = nullptr;
unsigned PushOpcode;
switch (Store->getOpcode()) {
default:
llvm_unreachable("Unexpected Opcode!");
case X86::AND16mi8:
case X86::AND32mi8:
case X86::AND64mi8:
case X86::OR16mi8:
case X86::OR32mi8:
case X86::OR64mi8:
case X86::MOV32mi:
case X86::MOV64mi32:
PushOpcode = Is64Bit ? X86::PUSH64i32 : X86::PUSHi32;
// If the operand is a small (8-bit) immediate, we can use a
// PUSH instruction with a shorter encoding.
// Note that isImm() may fail even though this is a MOVmi, because
// the operand can also be a symbol.
if (PushOp.isImm()) {
int64_t Val = PushOp.getImm();
if (isInt<8>(Val))
PushOpcode = Is64Bit ? X86::PUSH64i8 : X86::PUSH32i8;
}
Push = BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode)).add(PushOp);
break;
case X86::MOV32mr:
case X86::MOV64mr: {
unsigned int Reg = PushOp.getReg();
// If storing a 32-bit vreg on 64-bit targets, extend to a 64-bit vreg
// in preparation for the PUSH64. The upper 32 bits can be undef.
if (Is64Bit && Store->getOpcode() == X86::MOV32mr) {
unsigned UndefReg = MRI->createVirtualRegister(&X86::GR64RegClass);
Reg = MRI->createVirtualRegister(&X86::GR64RegClass);
BuildMI(MBB, Context.Call, DL, TII->get(X86::IMPLICIT_DEF), UndefReg);
BuildMI(MBB, Context.Call, DL, TII->get(X86::INSERT_SUBREG), Reg)
.addReg(UndefReg)
.add(PushOp)
.addImm(X86::sub_32bit);
}
// If PUSHrmm is not slow on this target, try to fold the source of the
// push into the instruction.
bool SlowPUSHrmm = STI->isAtom() || STI->isSLM();
// Check that this is legal to fold. Right now, we're extremely
// conservative about that.
MachineInstr *DefMov = nullptr;
if (!SlowPUSHrmm && (DefMov = canFoldIntoRegPush(FrameSetup, Reg))) {
PushOpcode = Is64Bit ? X86::PUSH64rmm : X86::PUSH32rmm;
Push = BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode));
unsigned NumOps = DefMov->getDesc().getNumOperands();
for (unsigned i = NumOps - X86::AddrNumOperands; i != NumOps; ++i)
Push->addOperand(DefMov->getOperand(i));
DefMov->eraseFromParent();
} else {
PushOpcode = Is64Bit ? X86::PUSH64r : X86::PUSH32r;
Push = BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode))
.addReg(Reg)
.getInstr();
}
break;
}
}
// For debugging, when using SP-based CFA, we need to adjust the CFA
// offset after each push.
// TODO: This is needed only if we require precise CFA.
if (!TFL->hasFP(MF))
TFL->BuildCFI(
MBB, std::next(Push), DL,
MCCFIInstruction::createAdjustCfaOffset(nullptr, SlotSize));
MBB.erase(Store);
}
// The stack-pointer copy is no longer used in the call sequences.
// There should not be any other users, but we can't commit to that, so:
if (Context.SPCopy && MRI->use_empty(Context.SPCopy->getOperand(0).getReg()))
Context.SPCopy->eraseFromParent();
// Once we've done this, we need to make sure PEI doesn't assume a reserved
// frame.
X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
FuncInfo->setHasPushSequences(true);
}
bool X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
// Check that this particular call sequence is amenable to the
// transformation.
const X86RegisterInfo &RegInfo = *static_cast<const X86RegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
unsigned StackPtr = RegInfo.getStackRegister();
int FrameDestroyOpcode = TII->getCallFrameDestroyOpcode();
// We expect to enter this at the beginning of a call sequence
assert(I->getOpcode() == TII->getCallFrameSetupOpcode());
MachineBasicBlock::iterator FrameSetup = I++;
// For globals in PIC mode, we can have some LEAs here.
// Ignore them, they don't bother us.
// TODO: Extend this to something that covers more cases.
while (I->getOpcode() == X86::LEA32r)
++I;
// We expect a copy instruction here.
// TODO: The copy instruction is a lowering artifact.
// We should also support a copy-less version, where the stack
// pointer is used directly.
if (!I->isCopy() || !I->getOperand(0).isReg())
return false;
MachineBasicBlock::iterator SPCopy = I++;
StackPtr = SPCopy->getOperand(0).getReg();
// Scan the call setup sequence for the pattern we're looking for.
// We only handle a simple case - a sequence of MOV32mi or MOV32mr
// instructions, that push a sequence of 32-bit values onto the stack, with
// no gaps between them.
SmallVector<MachineInstr*, 4> MovVector(4, nullptr);
unsigned int MaxAdjust = FrameSetup->getOperand(0).getImm() / 4;
if (MaxAdjust > 4)
MovVector.resize(MaxAdjust, nullptr);
do {
int Opcode = I->getOpcode();
if (Opcode != X86::MOV32mi && Opcode != X86::MOV32mr)
break;
// We only want movs of the form:
// movl imm/r32, k(%esp)
// If we run into something else, bail.
// Note that AddrBaseReg may, counter to its name, not be a register,
// but rather a frame index.
// TODO: Support the fi case. This should probably work now that we
// have the infrastructure to track the stack pointer within a call
// sequence.
if (!I->getOperand(X86::AddrBaseReg).isReg() ||
(I->getOperand(X86::AddrBaseReg).getReg() != StackPtr) ||
!I->getOperand(X86::AddrScaleAmt).isImm() ||
(I->getOperand(X86::AddrScaleAmt).getImm() != 1) ||
(I->getOperand(X86::AddrIndexReg).getReg() != X86::NoRegister) ||
(I->getOperand(X86::AddrSegmentReg).getReg() != X86::NoRegister) ||
!I->getOperand(X86::AddrDisp).isImm())
return false;
int64_t StackDisp = I->getOperand(X86::AddrDisp).getImm();
assert(StackDisp >= 0 && "Negative stack displacement when passing parameters");
// We really don't want to consider the unaligned case.
if (StackDisp % 4)
return false;
StackDisp /= 4;
assert((size_t)StackDisp < MovVector.size() &&
"Function call has more parameters than the stack is adjusted for.");
// If the same stack slot is being filled twice, something's fishy.
if (MovVector[StackDisp] != nullptr)
return false;
MovVector[StackDisp] = I;
++I;
} while (I != MBB.end());
// We now expect the end of the sequence - a call and a stack adjust.
if (I == MBB.end())
return false;
// For PCrel calls, we expect an additional COPY of the basereg.
// If we find one, skip it.
if (I->isCopy()) {
if (I->getOperand(1).getReg() ==
MF.getInfo<X86MachineFunctionInfo>()->getGlobalBaseReg())
++I;
else
return false;
}
if (!I->isCall())
return false;
MachineBasicBlock::iterator Call = I;
if ((++I)->getOpcode() != FrameDestroyOpcode)
return false;
// Now, go through the vector, and see that we don't have any gaps,
// but only a series of 32-bit MOVs.
int64_t ExpectedDist = 0;
auto MMI = MovVector.begin(), MME = MovVector.end();
for (; MMI != MME; ++MMI, ExpectedDist += 4)
if (*MMI == nullptr)
break;
// If the call had no parameters, do nothing
if (!ExpectedDist)
return false;
// We are either at the last parameter, or a gap.
// Make sure it's not a gap
for (; MMI != MME; ++MMI)
if (*MMI != nullptr)
return false;
// Ok, we can in fact do the transformation for this call.
// Do not remove the FrameSetup instruction, but adjust the parameters.
// PEI will end up finalizing the handling of this.
FrameSetup->getOperand(1).setImm(ExpectedDist);
DebugLoc DL = I->getDebugLoc();
// Now, iterate through the vector in reverse order, and replace the movs
// with pushes. MOVmi/MOVmr doesn't have any defs, so no need to
// replace uses.
for (int Idx = (ExpectedDist / 4) - 1; Idx >= 0; --Idx) {
MachineBasicBlock::iterator MOV = *MovVector[Idx];
MachineOperand PushOp = MOV->getOperand(X86::AddrNumOperands);
if (MOV->getOpcode() == X86::MOV32mi) {
unsigned PushOpcode = X86::PUSHi32;
// If the operand is a small (8-bit) immediate, we can use a
// PUSH instruction with a shorter encoding.
// Note that isImm() may fail even though this is a MOVmi, because
// the operand can also be a symbol.
if (PushOp.isImm()) {
int64_t Val = PushOp.getImm();
if (isInt<8>(Val))
PushOpcode = X86::PUSH32i8;
}
BuildMI(MBB, Call, DL, TII->get(PushOpcode)).addOperand(PushOp);
} else {
unsigned int Reg = PushOp.getReg();
// If PUSHrmm is not slow on this target, try to fold the source of the
// push into the instruction.
const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
bool SlowPUSHrmm = ST.isAtom() || ST.isSLM();
// Check that this is legal to fold. Right now, we're extremely
// conservative about that.
MachineInstr *DefMov = nullptr;
if (!SlowPUSHrmm && (DefMov = canFoldIntoRegPush(FrameSetup, Reg))) {
MachineInstr *Push = BuildMI(MBB, Call, DL, TII->get(X86::PUSH32rmm));
unsigned NumOps = DefMov->getDesc().getNumOperands();
for (unsigned i = NumOps - X86::AddrNumOperands; i != NumOps; ++i)
Push->addOperand(DefMov->getOperand(i));
DefMov->eraseFromParent();
} else {
BuildMI(MBB, Call, DL, TII->get(X86::PUSH32r)).addReg(Reg).getInstr();
}
}
MBB.erase(MOV);
}
// The stack-pointer copy is no longer used in the call sequences.
// There should not be any other users, but we can't commit to that, so:
if (MRI->use_empty(SPCopy->getOperand(0).getReg()))
SPCopy->eraseFromParent();
// Once we've done this, we need to make sure PEI doesn't assume a reserved
// frame.
X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
FuncInfo->setHasPushSequences(true);
return true;
}