diff options
Diffstat (limited to 'lib/Target/X86/X86FrameLowering.cpp')
| -rw-r--r-- | lib/Target/X86/X86FrameLowering.cpp | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp index 9d66bfd88a..5db431b60a 100644 --- a/lib/Target/X86/X86FrameLowering.cpp +++ b/lib/Target/X86/X86FrameLowering.cpp @@ -914,11 +914,14 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const { .addReg(X86::EFLAGS, RegState::Define | RegState::Implicit) .setMIFlag(MachineInstr::FrameSetup); - // MSVC x64's __chkstk needs to adjust %rsp. - // FIXME: %rax preserves the offset and should be available. - if (isSPUpdateNeeded) - emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, IsLP64, - UseLEA, TII, *RegInfo); + // MSVC x64's __chkstk does not adjust %rsp itself. + // It also does not clobber %rax so we can reuse it when adjusting %rsp. + if (isSPUpdateNeeded) { + BuildMI(MBB, MBBI, DL, TII.get(X86::SUB64rr), StackPtr) + .addReg(StackPtr) + .addReg(X86::RAX) + .setMIFlag(MachineInstr::FrameSetup); + } if (isEAXAlive) { // Restore EAX |