[PATCH] D42898: Do not spill CSR to stack on entry to noreturn functions

[pmb via Phabricator via llvm-commits]

myeisha created this revision.
Herald added subscribers: llvm-commits, kbarton, javed.absar, nemanjai.

A noreturn function can be expected to never return, and by never returning it will also never have to restore any callee-saved registers for its caller. This makes it possible to skip spills of those registers during function entry, saving some stack space and time in the process. This is rather useful for embedded targets with limited stack space.

Initially reported as PR#9970.


Repository:
  rL LLVM

https://reviews.llvm.org/D42898

Files:
  lib/CodeGen/TargetFrameLoweringImpl.cpp
  test/CodeGen/AArch64/arm64-shrink-wrapping.ll
  test/CodeGen/ARM/arm-shrink-wrapping.ll
  test/CodeGen/ARM/noreturn-csr-skip.ll
  test/CodeGen/PowerPC/ppc-shrink-wrapping.ll
  test/CodeGen/Thumb/thumb-shrink-wrapping.ll
  test/CodeGen/X86/2010-02-19-TailCallRetAddrBug.ll
  test/CodeGen/X86/x86-shrink-wrapping.ll

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