[PATCH] D84152: [PowerPC] Fix wrong codegen when stack pointer has to realign

[Kai Luo via Phabricator via llvm-commits]

lkail created this revision.
lkail added reviewers: PowerPC, jsji, steven.zhang.
Herald added subscribers: llvm-commits, shchenz, kbarton, hiraditya, nemanjai.
Herald added a project: LLVM.

Current powerpc backend generates wrong code sequence if stack pointer has to realign if `-fstack-clash-protection` enabled. There are two situations

1. Current `PREPARE_PROBED_ALLOCA` takes `NegSizeReg` as input and returns

`FinalStackPtr`. `FinalStackPtr=StackPtr+ActualNegSize` is calculated correctly, however code following `PREPARE_PROBED_ALLOCA` still uses value of `NegSizeReg`, which does not contain `ActualNegSize` if `MaxAlign > TargetAlign`, to calculate loop trip count and residual number of bytes.

2. When `HasBP && MaxAlign > 1`, the backend should generate a subtraction instruction rather than a `stux` instruction.

This patch fixes https://bugs.llvm.org/show_bug.cgi?id=46759


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84152

Files:
  llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.cpp
  llvm/lib/Target/PowerPC/PPCInstr64Bit.td
  llvm/lib/Target/PowerPC/PPCInstrInfo.td
  llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
  llvm/test/CodeGen/PowerPC/pr46759.ll
  llvm/test/CodeGen/PowerPC/stack-clash-dynamic-alloca.ll

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