[PATCH] D135687: [AArch64] Fix aligning the stack after calling __chkstk

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo updated this revision to Diff 467717.
mstorsjo added a comment.

Added a testcase for one case where things broke in practice with the previous form.

Since the previous version, I moved the setting of `NeedsRealignment` further down in the function. Previously I initialized this variable early in the function, before the first call to `windowsRequiresStackProbe`. However, `NumBytes` may be nonzero at this point (making `NeedsRealignment` true), even if `NumBytes` would be zero at the point when realignment is done later in the function, prior to the patch.

We don't need to include `RealignmentPadding` in the first initial check with `windowsRequiresStackProbe`, since if we're actually going to realign the stack, we do have a stack frame anyway.

Additionally, don't set `RealignmentPadding` to a nonzero value, if the requested alignment is less than 16. In the added testcase, `MFI.getMaxAlign()` is 8. (Curiously, for non-Windows OSes, this input actually does result in generating code for ANDing the stack pointer to align it to 8 bytes though.)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D135687/new/

https://reviews.llvm.org/D135687

Files:
  llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
  llvm/test/CodeGen/AArch64/win-align-chkstk.ll
  llvm/test/CodeGen/AArch64/win-realign.ll

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