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X86: Stop dereferencing end() in X86FrameLowering::emitEpilogue 

On a Windows build of Chromium, r278532 (up to r278539)
X86FrameLowering::emitEpilogue because it wasn't wary enough of the
return of MachineBasicBlock::getFirstTerminator.  Guard all the uses
here.

Note that r278532 *looks* like an NFC commit (just an API change), but
it removes a couple of layers of abstraction and is probably causing
optimization differences in MSVC.

llvm-svn: 278572
This commit is contained in:
Duncan P. N. Exon Smith 2016-08-12 22:43:33 +00:00
parent 6ee00a2602
commit 69b0650548
1 changed files with 7 additions and 5 deletions
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12
llvm/lib/Target/X86/X86FrameLowering.cpp
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@ -1480,7 +1480,9 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
const MachineFrameInfo &MFI = MF.getFrameInfo();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
unsigned RetOpcode = MBBI->getOpcode();
Optional<unsigned> RetOpcode;
if (MBBI != MBB.end())
RetOpcode = MBBI->getOpcode();
DebugLoc DL;
if (MBBI != MBB.end())
DL = MBBI->getDebugLoc();
@ -1493,7 +1495,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
bool IsWin64Prologue = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
bool NeedsWinCFI =
IsWin64Prologue && MF.getFunction()->needsUnwindTableEntry();
bool IsFunclet = isFuncletReturnInstr(*MBBI);
bool IsFunclet = MBBI == MBB.end() ? false : isFuncletReturnInstr(*MBBI);
MachineBasicBlock *TargetMBB = nullptr;
// Get the number of bytes to allocate from the FrameInfo.
@ -1502,7 +1504,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
unsigned CSSize = X86FI->getCalleeSavedFrameSize();
uint64_t NumBytes = 0;
if (MBBI->getOpcode() == X86::CATCHRET) {
if (RetOpcode && *RetOpcode == X86::CATCHRET) {
// SEH shouldn't use catchret.
assert(!isAsynchronousEHPersonality(
classifyEHPersonality(MF.getFunction()->getPersonalityFn())) &&
@ -1516,7 +1518,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::POP64r : X86::POP32r),
MachineFramePtr)
.setMIFlag(MachineInstr::FrameDestroy);
} else if (MBBI->getOpcode() == X86::CLEANUPRET) {
} else if (RetOpcode && *RetOpcode == X86::CLEANUPRET) {
NumBytes = getWinEHFuncletFrameSize(MF);
assert(hasFP(MF) && "EH funclets without FP not yet implemented");
BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::POP64r : X86::POP32r),
@ -1629,7 +1631,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
if (NeedsWinCFI)
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_Epilogue));
if (!isTailCallOpcode(RetOpcode)) {
if (!RetOpcode || !isTailCallOpcode(*RetOpcode)) {
// Add the return addr area delta back since we are not tail calling.
int Offset = -1 * X86FI->getTCReturnAddrDelta();
assert(Offset >= 0 && "TCDelta should never be positive");