[PATCH] D58632: [X86] Improve lowering of idemptotent RMW operations

[JF Bastien via Phabricator via llvm-commits]

jfb added inline comments.


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Comment at: lib/Target/X86/X86ISelLowering.cpp:26255
+
+  bool HasRedZone = Subtarget.isTargetLinux() && Subtarget.isTarget64BitLP64(); 
+  int SPOffset = HasRedZone ? -8 : 0;
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I'd rather see something more precise here.

We have a `noredzone` function attribute which should be honored:
https://releases.llvm.org/3.7.0/docs/LangRef.html#id630

aarch64 has some handling for redzone too:
https://llvm.org/doxygen/AArch64FrameLowering_8cpp_source.html#l00186

So does X86FrameLowering.cpp, X86InstrInfo.cpp, and X86MachineFunctionInfo.h.

Some other architectures to this too. I think you should do the same: if the attribute isn't present, redzone away. If some targets don't have a redzone yet don't set the attribute, they've already opened themselves to pain. Maybe we need a PSA on the mailing list to make sure these targets set `noredzone` on all their functions.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D58632/new/

https://reviews.llvm.org/D58632