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[PPC][AIX] Save/restore r31 when using base pointer #100182

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Aug 7, 2024
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[PPC][AIX] Save/restore r31 when using base pointer #100182

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e5fd2aa
[PPC][AIX] Set needsFP to true when base pointer is used in prologue/…
Jul 23, 2024
069da92
Address review comments
Jul 29, 2024
f379cf4
Address review comments, fix formatting
Jul 29, 2024
d0a2452
Address review comments
Aug 1, 2024
4545ed6
Fix testcase comment
Aug 1, 2024
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14 changes: 12 additions & 2 deletions llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1007,7 +1007,7 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF,
// R0 cannot be used as a base register, but it can be used as an
// index in a store-indexed.
int LastOffset = 0;
if (HasFP) {
if (HasFP) {
// R0 += (FPOffset-LastOffset).
// Need addic, since addi treats R0 as 0.
BuildMI(MBB, MBBI, dl, TII.get(PPC::ADDIC), ScratchReg)
Expand Down Expand Up @@ -2025,8 +2025,18 @@ void PPCFrameLowering::determineCalleeSaves(MachineFunction &MF,
// 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))
if (RegInfo->hasBasePointer(MF)) {
SavedRegs.reset(RegInfo->getBaseRegister(MF));
// On AIX, when BaseRegister(R30) is used, need to spill r31 too to match
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nit: maybe it's good to make R30 and r31 be consistent, my bad : )

// AIX trackback table requirement.
if (!needsFP(MF) && !SavedRegs.test(isPPC64 ? PPC::X31 : PPC::R31) &&
Subtarget.isAIXABI()) {
assert(
(RegInfo->getBaseRegister(MF) == (isPPC64 ? PPC::X30 : PPC::R30)) &&
"Invalid base register on AIX!");
SavedRegs.set(isPPC64 ? PPC::X31 : PPC::R31);
}
}
if (FI->usesPICBase())
SavedRegs.reset(PPC::R30);

Expand Down
5 changes: 5 additions & 0 deletions llvm/test/CodeGen/PowerPC/aix-base-pointer.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@

; Use an overaligned buffer to force base-pointer usage. Test verifies:
; - base pointer register (r30) is saved/defined/restored.
; - frame pointer register (r31) is saved/defined/restored.
; - stack frame is allocated with correct alignment.
; - Address of %AlignedBuffer is calculated based off offset from the stack
; pointer.
Expand All @@ -25,7 +26,9 @@ declare void @callee(ptr)
; 32BIT: subfic 0, 0, -224
; 32BIT: stwux 1, 1, 0
; 32BIT: addi 3, 1, 64
; 32BIT: stw 31, -12(30)
; 32BIT: bl .callee
; 32BIT: lwz 31, -12(30)
; 32BIT: mr 1, 30
; 32BIT: lwz 30, -16(1)

Expand All @@ -36,6 +39,8 @@ declare void @callee(ptr)
; 64BIT: subfic 0, 0, -288
; 64BIT: stdux 1, 1, 0
; 64BIT: addi 3, 1, 128
; 64BIT: std 31, -16(30)
; 64BIT: bl .callee
; 64BIT: ld 31, -16(30)
; 64BIT: mr 1, 30
; 64BIT: ld 30, -24(1)
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