[PATCH] D151400: [X86] Align stack to 16-bytes on 32-bit with X86_INTR call convention

[Antonio Abbatangelo via Phabricator via llvm-commits]

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Adds a dynamic stack alignment to functions under the interrupt call
convention on x86-32. This fixes the issue where the stack can be
misaligned on entry, since x86-32 makes no guarantees about the stack
pointer position when the interrupt service routine is called.

The alignment is done by overriding X86RegisterInfo::shouldRealignStack,
and by setting the correct alignment in X86FrameLowering::calculateMaxStackAlign.
This forces the interrupt handler to be dynamically aligned, generating
the appropriate `and` instruction in the prologue and `lea` in the
epilogue. The `no-realign-stack` attribute can be used as an opt-out.

Fixes #26851


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D151400

Files:
  llvm/lib/Target/X86/X86FrameLowering.cpp
  llvm/lib/Target/X86/X86RegisterInfo.cpp
  llvm/lib/Target/X86/X86RegisterInfo.h
  llvm/test/CodeGen/X86/x86-32-intrcc.ll
  llvm/test/CodeGen/X86/x86-interrupt_cc.ll

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