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

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

After staring at my code sequence a bit more, it simplifies to:

  mov x15, #(NumBytes/16)
  mov x9, sp
  ubfx x9, x9, #4, #AlignBits
  add x15, x15, x9
  bl __chkstk
  sub sp, sp, x15, lsl #4

Your suggested sequence also works, I guess, but it feels a little weird to overallocate, then deallocate the extra memory.

MSVC doesn't actually realign the stack in the sense LLVM does; it just overallocates stack memory, then uses masking to align the addresses of variables.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D135687/new/

https://reviews.llvm.org/D135687