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[PowerPC] Don't spill the frame pointer twice

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When a function contains something, such as inline asm, which explicitly
clobbers the register used as the frame pointer, don't spill it twice. If we
need a frame pointer, it will be saved/restored in the prologue/epilogue code.
Explicitly spilling it again will reuse the same spill slot used by the
prologue/epilogue code, thus clobbering the saved value. The same applies
to the base-pointer or PIC-base register.

Partially fixes PR26856. Thanks to Ulrich for his analysis and the small
inline-asm reproducer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280188 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2016-08-31 00:52:03 +00:00
parent b6a139826b
commit 982b9c9736
2 changed files with 37 additions and 0 deletions
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11
lib/Target/PowerPC/PPCFrameLowering.cpp
View File

@ -1419,6 +1419,17 @@ void PPCFrameLowering::determineCalleeSaves(MachineFunction &MF,
FI->setPICBasePointerSaveIndex(PBPSI);
}
// Make sure we don't explicitly spill r31, because, for example, we have
// some inline asm which explicity clobbers it, when we otherwise have a
// frame pointer and are using r31's spill slot for the prologue/epilogue
// code. Same goes for the base pointer and the PIC base register.
if (needsFP(MF))
SavedRegs.reset(isPPC64 ? PPC::X31 : PPC::R31);
if (RegInfo->hasBasePointer(MF))
SavedRegs.reset(RegInfo->getBaseRegister(MF));
if (FI->usesPICBase())
SavedRegs.reset(PPC::R30);
// Reserve stack space to move the linkage area to in case of a tail call.
int TCSPDelta = 0;
if (MF.getTarget().Options.GuaranteedTailCallOpt &&

26
test/CodeGen/PowerPC/no-dup-spill-fp.ll Normal file
View File

@ -0,0 +1,26 @@
; RUN: llc < %s | FileCheck %s
target datalayout = "E-m:e-i64:64-n32:64"
target triple = "powerpc64"
; Function Attrs: nounwind
define void @test() #0 {
entry:
call void @func()
call void asm sideeffect "nop", "~{r31}"() #1, !srcloc !0
ret void
; CHECK-LABEL: @test
; CHECK: std 31, -8(1)
; CHECK: stdu 1, -{{[0-9]+}}(1)
; CHECK-NOT: std 31,
; CHECK: bl func
; CHECK: ld 31, -8(1)
; CHECK: blr
}
declare void @func()
attributes #0 = { nounwind "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "target-cpu"="ppc64" }
attributes #1 = { nounwind }
!0 = !{i32 57}