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Reuse %rax after calling __chkstk on win64

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Reapply this as I reverted the wrong commit.

llvm-svn: 185807
This commit is contained in:
Nico Rieck 2013-07-08 11:20:11 +00:00
parent 90555b76a0
commit 7230f0d23f
3 changed files with 10 additions and 8 deletions
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13
lib/Target/X86/X86FrameLowering.cpp
View File

@ -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

3
lib/Target/X86/X86ISelLowering.cpp
View File

@ -14432,12 +14432,11 @@ 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);

2
test/CodeGen/X86/win64_alloca_dynalloca.ll
View File

@ -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