diff options
| -rw-r--r-- | lib/Target/X86/X86FrameLowering.cpp | 13 | ||||
| -rw-r--r-- | lib/Target/X86/X86ISelLowering.cpp | 3 | ||||
| -rw-r--r-- | test/CodeGen/X86/win64_alloca_dynalloca.ll | 2 |
3 files changed, 10 insertions, 8 deletions
diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp index 9d66bfd..5db431b 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 diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp index a6e894b..aaeaa5d 100644 --- a/lib/Target/X86/X86ISelLowering.cpp +++ b/lib/Target/X86/X86ISelLowering.cpp @@ -14434,12 +14434,11 @@ X86TargetLowering::EmitLoweredWinAlloca(MachineInstr *MI, } else { // __chkstk(MSVCRT): does not update stack pointer. // Clobbers R10, R11 and EFLAGS. - // FIXME: RAX(allocated size) might be reused and not killed. BuildMI(*BB, MI, DL, TII->get(X86::W64ALLOCA)) .addExternalSymbol("__chkstk") .addReg(X86::RAX, RegState::Implicit) .addReg(X86::EFLAGS, RegState::Define | RegState::Implicit); - // RAX has the offset to subtracted from RSP. + // RAX has the offset to be subtracted from RSP. BuildMI(*BB, MI, DL, TII->get(X86::SUB64rr), X86::RSP) .addReg(X86::RSP) .addReg(X86::RAX); diff --git a/test/CodeGen/X86/win64_alloca_dynalloca.ll b/test/CodeGen/X86/win64_alloca_dynalloca.ll index cc11e4c..275ebf9 100644 --- a/test/CodeGen/X86/win64_alloca_dynalloca.ll +++ b/test/CodeGen/X86/win64_alloca_dynalloca.ll @@ -19,7 +19,7 @@ entry: ; W64: movq %rsp, %rbp ; W64: $4096, %rax ; W64: callq __chkstk -; W64: subq $4096, %rsp +; W64: subq %rax, %rsp ; Freestanding ; EFI: movq %rsp, %rbp |