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Pull in r282174 from upstream llvm trunk (by Krzysztof Parzyszek):

Browse Source 
[PPC] Set SP after loading data from stack frame, if no red zone is
  present

  Follow-up to r280705: Make sure that the SP is only restored after
  all data is loaded from the stack frame, if there is no red zone.

  This completes the fix for
  https://llvm.org/bugs/show_bug.cgi?id=26519.

  Differential Revision: https://reviews.llvm.org/D24466

Reported by:    Mark Millard
PR:             214433
This commit is contained in:
Dimitry Andric 2016-11-25 18:01:32 +00:00
parent cdaf963483
commit 26aa2dc584
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=309147
1 changed files with 198 additions and 53 deletions
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251
contrib/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
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@ -927,7 +927,7 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF,
}
// Have we generated a STUX instruction to claim stack frame? If so,
// the frame size will be placed in ScratchReg.
// the negated frame size will be placed in ScratchReg.
bool HasSTUX = false;
// This condition must be kept in sync with canUseAsPrologue.
@ -987,33 +987,88 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF,
if (!HasRedZone) {
assert(!isPPC64 && "A red zone is always available on PPC64");
if (HasSTUX) {
// The frame size is in ScratchReg, and the SPReg has been advanced
// (downwards) by the frame size: SPReg = old SPReg + ScratchReg.
// Set ScratchReg to the original SPReg: ScratchReg = SPReg - ScratchReg.
// The negated frame size is in ScratchReg, and the SPReg has been
// decremented by the frame size: SPReg = old SPReg + ScratchReg.
// Since FPOffset, PBPOffset, etc. are relative to the beginning of
// the stack frame (i.e. the old SP), ideally, we would put the old
// SP into a register and use it as the base for the stores. The
// problem is that the only available register may be ScratchReg,
// which could be R0, and R0 cannot be used as a base address.
// First, set ScratchReg to the old SP. This may need to be modified
// later.
BuildMI(MBB, MBBI, dl, TII.get(PPC::SUBF), ScratchReg)
.addReg(ScratchReg, RegState::Kill)
.addReg(SPReg);
// Now that the stack frame has been allocated, save all the necessary
// registers using ScratchReg as the base address.
if (HasFP)
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(FPReg)
.addImm(FPOffset)
.addReg(ScratchReg);
if (FI->usesPICBase())
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(PPC::R30)
.addImm(PBPOffset)
.addReg(ScratchReg);
if (HasBP) {
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(BPReg)
.addImm(BPOffset)
.addReg(ScratchReg);
BuildMI(MBB, MBBI, dl, OrInst, BPReg)
.addReg(ScratchReg, RegState::Kill)
.addReg(ScratchReg);
if (ScratchReg == PPC::R0) {
// R0 cannot be used as a base register, but it can be used as an
// index in a store-indexed.
int LastOffset = 0;
if (HasFP) {
// R0 += (FPOffset-LastOffset).
// Need addic, since addi treats R0 as 0.
BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDIC), ScratchReg)
.addReg(ScratchReg)
.addImm(FPOffset-LastOffset);
LastOffset = FPOffset;
// Store FP into *R0.
BuildMI(MBB, MBBI, dl, TII.get(PPC::STWX))
.addReg(FPReg, RegState::Kill) // Save FP.
.addReg(PPC::ZERO)
.addReg(ScratchReg); // This will be the index (R0 is ok here).
}
if (FI->usesPICBase()) {
// R0 += (PBPOffset-LastOffset).
BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDIC), ScratchReg)
.addReg(ScratchReg)
.addImm(PBPOffset-LastOffset);
LastOffset = PBPOffset;
BuildMI(MBB, MBBI, dl, TII.get(PPC::STWX))
.addReg(PPC::R30, RegState::Kill) // Save PIC base pointer.
.addReg(PPC::ZERO)
.addReg(ScratchReg); // This will be the index (R0 is ok here).
}
if (HasBP) {
// R0 += (BPOffset-LastOffset).
BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDIC), ScratchReg)
.addReg(ScratchReg)
.addImm(BPOffset-LastOffset);
LastOffset = BPOffset;
BuildMI(MBB, MBBI, dl, TII.get(PPC::STWX))
.addReg(BPReg, RegState::Kill) // Save BP.
.addReg(PPC::ZERO)
.addReg(ScratchReg); // This will be the index (R0 is ok here).
// BP = R0-LastOffset
BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDIC), BPReg)
.addReg(ScratchReg, RegState::Kill)
.addImm(-LastOffset);
}
} else {
// ScratchReg is not R0, so use it as the base register. It is
// already set to the old SP, so we can use the offsets directly.
// Now that the stack frame has been allocated, save all the necessary
// registers using ScratchReg as the base address.
if (HasFP)
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(FPReg)
.addImm(FPOffset)
.addReg(ScratchReg);
if (FI->usesPICBase())
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(PPC::R30)
.addImm(PBPOffset)
.addReg(ScratchReg);
if (HasBP) {
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(BPReg)
.addImm(BPOffset)
.addReg(ScratchReg);
BuildMI(MBB, MBBI, dl, OrInst, BPReg)
.addReg(ScratchReg, RegState::Kill)
.addReg(ScratchReg);
}
}
} else {
// The frame size is a known 16-bit constant (fitting in the immediate
@ -1191,6 +1246,7 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
// Do we have a frame pointer and/or base pointer for this function?
bool HasFP = hasFP(MF);
bool HasBP = RegInfo->hasBasePointer(MF);
bool HasRedZone = Subtarget.isPPC64() || !Subtarget.isSVR4ABI();
unsigned SPReg = isPPC64 ? PPC::X1 : PPC::R1;
unsigned BPReg = RegInfo->getBaseRegister(MF);
@ -1203,6 +1259,8 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
: PPC::LWZ );
const MCInstrDesc& LoadImmShiftedInst = TII.get( isPPC64 ? PPC::LIS8
: PPC::LIS );
const MCInstrDesc& OrInst = TII.get(isPPC64 ? PPC::OR8
: PPC::OR );
const MCInstrDesc& OrImmInst = TII.get( isPPC64 ? PPC::ORI8
: PPC::ORI );
const MCInstrDesc& AddImmInst = TII.get( isPPC64 ? PPC::ADDI8
@ -1224,10 +1282,9 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
if (HasFP) {
if (isSVR4ABI) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int FPIndex = FI->getFramePointerSaveIndex();
assert(FPIndex && "No Frame Pointer Save Slot!");
FPOffset = FFI->getObjectOffset(FPIndex);
FPOffset = MFI->getObjectOffset(FPIndex);
} else {
FPOffset = getFramePointerSaveOffset();
}
@ -1236,10 +1293,9 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
int BPOffset = 0;
if (HasBP) {
if (isSVR4ABI) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int BPIndex = FI->getBasePointerSaveIndex();
assert(BPIndex && "No Base Pointer Save Slot!");
BPOffset = FFI->getObjectOffset(BPIndex);
BPOffset = MFI->getObjectOffset(BPIndex);
} else {
BPOffset = getBasePointerSaveOffset();
}
@ -1247,10 +1303,9 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
int PBPOffset = 0;
if (FI->usesPICBase()) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int PBPIndex = FI->getPICBasePointerSaveIndex();
assert(PBPIndex && "No PIC Base Pointer Save Slot!");
PBPOffset = FFI->getObjectOffset(PBPIndex);
PBPOffset = MFI->getObjectOffset(PBPIndex);
}
bool IsReturnBlock = (MBBI != MBB.end() && MBBI->isReturn());
@ -1283,9 +1338,25 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
// indexed into with a simple LD/LWZ immediate offset operand.
bool isLargeFrame = !isInt<16>(FrameSize);
// On targets without red zone, the SP needs to be restored last, so that
// all live contents of the stack frame are upwards of the SP. This means
// that we cannot restore SP just now, since there may be more registers
// to restore from the stack frame (e.g. R31). If the frame size is not
// a simple immediate value, we will need a spare register to hold the
// restored SP. If the frame size is known and small, we can simply adjust
// the offsets of the registers to be restored, and still use SP to restore
// them. In such case, the final update of SP will be to add the frame
// size to it.
// To simplify the code, set RBReg to the base register used to restore
// values from the stack, and set SPAdd to the value that needs to be added
// to the SP at the end. The default values are as if red zone was present.
unsigned RBReg = SPReg;
unsigned SPAdd = 0;
if (FrameSize) {
// In the prologue, the loaded (or persistent) stack pointer value is offset
// by the STDU/STDUX/STWU/STWUX instruction. Add this offset back now.
// In the prologue, the loaded (or persistent) stack pointer value is
// offset by the STDU/STDUX/STWU/STWUX instruction. For targets with red
// zone add this offset back now.
// If this function contained a fastcc call and GuaranteedTailCallOpt is
// enabled (=> hasFastCall()==true) the fastcc call might contain a tail
@ -1293,8 +1364,10 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
// value of R31 in this case.
if (FI->hasFastCall()) {
assert(HasFP && "Expecting a valid frame pointer.");
if (!HasRedZone)
RBReg = FPReg;
if (!isLargeFrame) {
BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
BuildMI(MBB, MBBI, dl, AddImmInst, RBReg)
.addReg(FPReg).addImm(FrameSize);
} else {
BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
@ -1303,27 +1376,55 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
.addReg(ScratchReg, RegState::Kill)
.addImm(FrameSize & 0xFFFF);
BuildMI(MBB, MBBI, dl, AddInst)
.addReg(SPReg)
.addReg(RBReg)
.addReg(FPReg)
.addReg(ScratchReg);
}
} else if (!isLargeFrame && !HasBP && !MFI->hasVarSizedObjects()) {
BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
.addReg(SPReg)
.addImm(FrameSize);
if (HasRedZone) {
BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
.addReg(SPReg)
.addImm(FrameSize);
} else {
// Make sure that adding FrameSize will not overflow the max offset
// size.
assert(FPOffset <= 0 && BPOffset <= 0 && PBPOffset <= 0 &&
"Local offsets should be negative");
SPAdd = FrameSize;
FPOffset += FrameSize;
BPOffset += FrameSize;
PBPOffset += FrameSize;
}
} else {
BuildMI(MBB, MBBI, dl, LoadInst, SPReg)
// We don't want to use ScratchReg as a base register, because it
// could happen to be R0. Use FP instead, but make sure to preserve it.
if (!HasRedZone) {
// If FP is not saved, copy it to ScratchReg.
if (!HasFP)
BuildMI(MBB, MBBI, dl, OrInst, ScratchReg)
.addReg(FPReg)
.addReg(FPReg);
RBReg = FPReg;
}
BuildMI(MBB, MBBI, dl, LoadInst, RBReg)
.addImm(0)
.addReg(SPReg);
}
}
assert(RBReg != ScratchReg && "Should have avoided ScratchReg");
// If there is no red zone, ScratchReg may be needed for holding a useful
// value (although not the base register). Make sure it is not overwritten
// too early.
assert((isPPC64 || !MustSaveCR) &&
"Epilogue CR restoring supported only in 64-bit mode");
// If we need to save both the LR and the CR and we only have one available
// scratch register, we must do them one at a time.
// If we need to restore both the LR and the CR and we only have one
// available scratch register, we must do them one at a time.
if (MustSaveCR && SingleScratchReg && MustSaveLR) {
// Here TempReg == ScratchReg, and in the absence of red zone ScratchReg
// is live here.
assert(HasRedZone && "Expecting red zone");
BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ8), TempReg)
.addImm(8)
.addReg(SPReg);
@ -1332,33 +1433,77 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
.addReg(TempReg, getKillRegState(i == e-1));
}
if (MustSaveLR)
// Delay restoring of the LR if ScratchReg is needed. This is ok, since
// LR is stored in the caller's stack frame. ScratchReg will be needed
// if RBReg is anything other than SP. We shouldn't use ScratchReg as
// a base register anyway, because it may happen to be R0.
bool LoadedLR = false;
if (MustSaveLR && RBReg == SPReg && isInt<16>(LROffset+SPAdd)) {
BuildMI(MBB, MBBI, dl, LoadInst, ScratchReg)
.addImm(LROffset)
.addReg(SPReg);
.addImm(LROffset+SPAdd)
.addReg(RBReg);
LoadedLR = true;
}
if (MustSaveCR &&
!(SingleScratchReg && MustSaveLR)) // will only occur for PPC64
if (MustSaveCR && !(SingleScratchReg && MustSaveLR)) {
// This will only occur for PPC64.
assert(isPPC64 && "Expecting 64-bit mode");
assert(RBReg == SPReg && "Should be using SP as a base register");
BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ8), TempReg)
.addImm(8)
.addReg(SPReg);
.addReg(RBReg);
}
if (HasFP)
BuildMI(MBB, MBBI, dl, LoadInst, FPReg)
.addImm(FPOffset)
.addReg(SPReg);
if (HasFP) {
// If there is red zone, restore FP directly, since SP has already been
// restored. Otherwise, restore the value of FP into ScratchReg.
if (HasRedZone || RBReg == SPReg)
BuildMI(MBB, MBBI, dl, LoadInst, FPReg)
.addImm(FPOffset)
.addReg(SPReg);
else
BuildMI(MBB, MBBI, dl, LoadInst, ScratchReg)
.addImm(FPOffset)
.addReg(RBReg);
}
if (FI->usesPICBase())
// FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
BuildMI(MBB, MBBI, dl, LoadInst)
.addReg(PPC::R30)
.addImm(PBPOffset)
.addReg(SPReg);
.addReg(RBReg);
if (HasBP)
BuildMI(MBB, MBBI, dl, LoadInst, BPReg)
.addImm(BPOffset)
.addReg(SPReg);
.addReg(RBReg);
// There is nothing more to be loaded from the stack, so now we can
// restore SP: SP = RBReg + SPAdd.
if (RBReg != SPReg || SPAdd != 0) {
assert(!HasRedZone && "This should not happen with red zone");
// If SPAdd is 0, generate a copy.
if (SPAdd == 0)
BuildMI(MBB, MBBI, dl, OrInst, SPReg)
.addReg(RBReg)
.addReg(RBReg);
else
BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
.addReg(RBReg)
.addImm(SPAdd);
assert(RBReg != ScratchReg && "Should be using FP or SP as base register");
if (RBReg == FPReg)
BuildMI(MBB, MBBI, dl, OrInst, FPReg)
.addReg(ScratchReg)
.addReg(ScratchReg);
// Now load the LR from the caller's stack frame.
if (MustSaveLR && !LoadedLR)
BuildMI(MBB, MBBI, dl, LoadInst, ScratchReg)
.addImm(LROffset)
.addReg(SPReg);
}
if (MustSaveCR &&
!(SingleScratchReg && MustSaveLR)) // will only occur for PPC64