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[X86] Refactor stack adjustments into X86FrameLowering::BuildStackAdjustment 

Deduplicates some code and lets us use LEA on atom when adjusting the
stack around callee-cleanup calls. This is the only intended
functionality change.

llvm-svn: 240044
This commit is contained in:
Reid Kleckner 2015-06-18 20:22:12 +00:00
parent 7bd29f2613
commit 98d7803291
3 changed files with 93 additions and 107 deletions
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9
llvm/lib/Target/X86/X86ExpandPseudo.cpp
View File

@ -84,14 +84,9 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
int StackAdj = StackAdjust.getImm();
if (StackAdj) {
// standard x86_64 and NaCl use 64-bit frame/stack pointers, x32 - 32-bit.
// Check if we should use LEA for SP.
const X86FrameLowering *TFI = STI->getFrameLowering();
bool UseLEAForSP = STI->useLeaForSP() &&
X86FL->canUseLEAForSPInEpilogue(*MBB.getParent());
// Check for possible merge with preceding ADD instruction.
StackAdj += TFI->mergeSPUpdates(MBB, MBBI, true);
TFI->emitSPUpdate(MBB, MBBI, StackAdj, UseLEAForSP);
StackAdj += X86FL->mergeSPUpdates(MBB, MBBI, true);
X86FL->emitSPUpdate(MBB, MBBI, StackAdj, /*InEpilogue=*/true);
}
// Jump to label or value in register.

182
llvm/lib/Target/X86/X86FrameLowering.cpp
View File

@ -214,20 +214,36 @@ static bool isEAXLiveIn(MachineFunction &MF) {
return false;
}
/// Check whether or not the terminators of \p MBB needs to read EFLAGS.
static bool terminatorsNeedFlagsAsInput(const MachineBasicBlock &MBB) {
for (const MachineInstr &MI : MBB.terminators()) {
bool BreakNext = false;
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (Reg != X86::EFLAGS)
continue;
// This terminator needs an eflag that is not defined
// by a previous terminator.
if (!MO.isDef())
return true;
BreakNext = true;
}
if (BreakNext)
break;
}
return false;
}
/// emitSPUpdate - Emit a series of instructions to increment / decrement the
/// stack pointer by a constant value.
void X86FrameLowering::emitSPUpdate(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
int64_t NumBytes, bool UseLEA) const {
int64_t NumBytes, bool InEpilogue) const {
bool isSub = NumBytes < 0;
uint64_t Offset = isSub ? -NumBytes : NumBytes;
unsigned Opc;
if (UseLEA)
Opc = getLEArOpcode(Uses64BitFramePtr);
else
Opc = isSub
? getSUBriOpcode(Uses64BitFramePtr, Offset)
: getADDriOpcode(Uses64BitFramePtr, Offset);
uint64_t Chunk = (1LL << 31) - 1;
DebugLoc DL = MBB.findDebugLoc(MBBI);
@ -244,7 +260,7 @@ void X86FrameLowering::emitSPUpdate(MachineBasicBlock &MBB,
Reg = findDeadCallerSavedReg(MBB, MBBI, RegInfo, Is64Bit);
if (Reg) {
Opc = Is64Bit ? X86::MOV64ri : X86::MOV32ri;
unsigned Opc = Is64Bit ? X86::MOV64ri : X86::MOV32ri;
BuildMI(MBB, MBBI, DL, TII.get(Opc), Reg)
.addImm(Offset);
Opc = isSub
@ -266,7 +282,7 @@ void X86FrameLowering::emitSPUpdate(MachineBasicBlock &MBB,
? (unsigned)(Is64Bit ? X86::RAX : X86::EAX)
: findDeadCallerSavedReg(MBB, MBBI, RegInfo, Is64Bit);
if (Reg) {
Opc = isSub
unsigned Opc = isSub
? (Is64Bit ? X86::PUSH64r : X86::PUSH32r)
: (Is64Bit ? X86::POP64r : X86::POP32r);
MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(Opc))
@ -278,25 +294,59 @@ void X86FrameLowering::emitSPUpdate(MachineBasicBlock &MBB,
}
}
MachineInstr *MI = nullptr;
if (UseLEA) {
MI = addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr),
StackPtr, false, isSub ? -ThisVal : ThisVal);
} else {
MI = BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr)
.addImm(ThisVal);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
}
MachineInstrBuilder MI = BuildStackAdjustment(
MBB, MBBI, DL, isSub ? -ThisVal : ThisVal, InEpilogue);
if (isSub)
MI->setFlag(MachineInstr::FrameSetup);
MI.setMIFlag(MachineInstr::FrameSetup);
Offset -= ThisVal;
}
}
MachineInstrBuilder X86FrameLowering::BuildStackAdjustment(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI, DebugLoc DL,
int64_t Offset, bool InEpilogue) const {
assert(Offset != 0 && "zero offset stack adjustment requested");
// On Atom, using LEA to adjust SP is preferred, but using it in the epilogue
// is tricky.
bool UseLEA;
if (!InEpilogue) {
UseLEA = STI.useLeaForSP();
} else {
// If we can use LEA for SP but we shouldn't, check that none
// of the terminators uses the eflags. Otherwise we will insert
// a ADD that will redefine the eflags and break the condition.
// Alternatively, we could move the ADD, but this may not be possible
// and is an optimization anyway.
UseLEA = canUseLEAForSPInEpilogue(*MBB.getParent());
if (UseLEA && !STI.useLeaForSP())
UseLEA = terminatorsNeedFlagsAsInput(MBB);
// If that assert breaks, that means we do not do the right thing
// in canUseAsEpilogue.
assert((UseLEA || !terminatorsNeedFlagsAsInput(MBB)) &&
"We shouldn't have allowed this insertion point");
}
MachineInstrBuilder MI;
if (UseLEA) {
MI = addRegOffset(BuildMI(MBB, MBBI, DL,
TII.get(getLEArOpcode(Uses64BitFramePtr)),
StackPtr),
StackPtr, false, Offset);
} else {
bool IsSub = Offset < 0;
uint64_t AbsOffset = IsSub ? -Offset : Offset;
unsigned Opc = IsSub ? getSUBriOpcode(Uses64BitFramePtr, AbsOffset)
: getADDriOpcode(Uses64BitFramePtr, AbsOffset);
MI = BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr)
.addImm(AbsOffset);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
}
return MI;
}
/// mergeSPUpdatesUp - Merge two stack-manipulating instructions upper iterator.
static
void mergeSPUpdatesUp(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
@ -602,7 +652,6 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
bool NeedsWinCFI = IsWin64Prologue && Fn->needsUnwindTableEntry();
bool NeedsDwarfCFI =
!IsWin64Prologue && (MMI.hasDebugInfo() || Fn->needsUnwindTableEntry());
bool UseLEA = STI.useLeaForSP();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
const unsigned MachineFramePtr =
STI.isTarget64BitILP32()
@ -652,14 +701,9 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
// applies to tail call optimized functions where the callee argument stack
// size is bigger than the callers.
if (TailCallReturnAddrDelta < 0) {
MachineInstr *MI =
BuildMI(MBB, MBBI, DL,
TII.get(getSUBriOpcode(Uses64BitFramePtr, -TailCallReturnAddrDelta)),
StackPtr)
.addReg(StackPtr)
.addImm(-TailCallReturnAddrDelta)
BuildStackAdjustment(MBB, MBBI, DL, TailCallReturnAddrDelta,
/*InEpilogue=*/false)
.setMIFlag(MachineInstr::FrameSetup);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
}
// Mapping for machine moves:
@ -856,7 +900,7 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
MBB.insert(MBBI, MI);
}
} else if (NumBytes) {
emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, UseLEA);
emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, /*InEpilogue=*/false);
}
if (NeedsWinCFI && NumBytes)
@ -958,29 +1002,6 @@ bool X86FrameLowering::canUseLEAForSPInEpilogue(
return !MF.getTarget().getMCAsmInfo()->usesWindowsCFI() || hasFP(MF);
}
/// Check whether or not the terminators of \p MBB needs to read EFLAGS.
static bool terminatorsNeedFlagsAsInput(const MachineBasicBlock &MBB) {
for (const MachineInstr &MI : MBB.terminators()) {
bool BreakNext = false;
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (Reg != X86::EFLAGS)
continue;
// This terminator needs an eflag that is not defined
// by a previous terminator.
if (!MO.isDef())
return true;
BreakNext = true;
}
if (BreakNext)
break;
}
return false;
}
void X86FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
@ -999,18 +1020,6 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
bool IsWin64Prologue = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
bool NeedsWinCFI =
IsWin64Prologue && MF.getFunction()->needsUnwindTableEntry();
bool UseLEAForSP = canUseLEAForSPInEpilogue(MF);
// If we can use LEA for SP but we shouldn't, check that none
// of the terminators uses the eflags. Otherwise we will insert
// a ADD that will redefine the eflags and break the condition.
// Alternatively, we could move the ADD, but this may not be possible
// and is an optimization anyway.
if (UseLEAForSP && !STI.useLeaForSP())
UseLEAForSP = terminatorsNeedFlagsAsInput(MBB);
// If that assert breaks, that means we do not do the right thing
// in canUseAsEpilogue.
assert((UseLEAForSP || !terminatorsNeedFlagsAsInput(MBB)) &&
"We shouldn't have allowed this insertion point");
// Get the number of bytes to allocate from the FrameInfo.
uint64_t StackSize = MFI->getStackSize();
@ -1087,7 +1096,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
}
} else if (NumBytes) {
// Adjust stack pointer back: ESP += numbytes.
emitSPUpdate(MBB, MBBI, NumBytes, UseLEAForSP);
emitSPUpdate(MBB, MBBI, NumBytes, /*InEpilogue=*/true);
--MBBI;
}
@ -1108,7 +1117,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
// Check for possible merge with preceding ADD instruction.
Offset += mergeSPUpdates(MBB, MBBI, true);
emitSPUpdate(MBB, MBBI, Offset, UseLEAForSP);
emitSPUpdate(MBB, MBBI, Offset, /*InEpilogue=*/true);
}
}
@ -1880,54 +1889,29 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
unsigned StackAlign = getStackAlignment();
Amount = RoundUpToAlignment(Amount, StackAlign);
MachineInstr *New = nullptr;
// Factor out the amount that gets handled inside the sequence
// (Pushes of argument for frame setup, callee pops for frame destroy)
Amount -= InternalAmt;
if (Amount) {
if (Opcode == TII.getCallFrameSetupOpcode()) {
New = BuildMI(MF, DL, TII.get(getSUBriOpcode(IsLP64, Amount)), StackPtr)
.addReg(StackPtr).addImm(Amount);
} else {
assert(Opcode == TII.getCallFrameDestroyOpcode());
unsigned Opc = getADDriOpcode(IsLP64, Amount);
New = BuildMI(MF, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr).addImm(Amount);
}
// Add Amount to SP to destroy a frame, and subtract to setup.
int Offset = isDestroy ? Amount : -Amount;
BuildStackAdjustment(MBB, I, DL, Offset, /*InEpilogue=*/false);
}
if (New) {
// The EFLAGS implicit def is dead.
New->getOperand(3).setIsDead();
// Replace the pseudo instruction with a new instruction.
MBB.insert(I, New);
}
return;
}
if (Opcode == TII.getCallFrameDestroyOpcode() && InternalAmt) {
if (isDestroy && InternalAmt) {
// If we are performing frame pointer elimination and if the callee pops
// something off the stack pointer, add it back. We do this until we have
// more advanced stack pointer tracking ability.
unsigned Opc = getSUBriOpcode(IsLP64, InternalAmt);
MachineInstr *New = BuildMI(MF, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr).addImm(InternalAmt);
// The EFLAGS implicit def is dead.
New->getOperand(3).setIsDead();
// We are not tracking the stack pointer adjustment by the callee, so make
// sure we restore the stack pointer immediately after the call, there may
// be spill code inserted between the CALL and ADJCALLSTACKUP instructions.
MachineBasicBlock::iterator B = MBB.begin();
while (I != B && !std::prev(I)->isCall())
--I;
MBB.insert(I, New);
BuildStackAdjustment(MBB, I, DL, -InternalAmt, /*InEpilogue=*/false);
}
}

9
llvm/lib/Target/X86/X86FrameLowering.h
View File

@ -18,6 +18,7 @@
namespace llvm {
class MachineInstrBuilder;
class MCCFIInstruction;
class X86Subtarget;
class X86RegisterInfo;
@ -112,7 +113,7 @@ public:
/// Emit a series of instructions to increment / decrement the stack
/// pointer by a constant value.
void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
int64_t NumBytes, bool UseLEA) const;
int64_t NumBytes, bool InEpilogue) const;
/// Check that LEA can be used on SP in an epilogue sequence for \p MF.
bool canUseLEAForSPInEpilogue(const MachineFunction &MF) const;
@ -144,6 +145,12 @@ private:
void BuildStackAlignAND(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI, DebugLoc DL,
uint64_t MaxAlign) const;
/// Adjusts the stack pointer using LEA, SUB, or ADD.
MachineInstrBuilder BuildStackAdjustment(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
DebugLoc DL, int64_t Offset,
bool InEpilogue) const;
};
} // End llvm namespace