[PATCH] D78717: [SystemZ] Implement -fstack-clash-protection

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa updated this revision to Diff 263129.
jonpa added a comment.

> As to the stack probe size, I think must indeed ensure that this size is also a multiple of 8 bytes (the stack alignment requirement) and is nonzero. If the given value doesn't fulfil those requirements, I guess we should round it down to the stack alignment requirement, and if the result is zero, use the stack alginment requirement instead.

I implemented this in getStackProbeSize() with a few new tests.

> I think just having a plain loop is OK for now. For any future optimizations, we'd have to do performance evaluation first.

I built and ran SPEC'17 once and it looked like there were no sign of regressions, at most a single percent...

> It seems this was added in preparation for exploiting "natural probes" -- if the code can be proven to already touch all (or at least some) stack pages at least once (in this test case via the stores), then we might optimize out some of the extra probes. But apparently this wasn't implemented in the X86 back-end in the end, and neither is it in your patch, so it doesn't make sense to have a test for it.

Ah, now I get it. Removed those tests.

> I believe this is also related to natural probes: on *Intel*, every call instruction would be a natural probe as it pushes the return address to the stack. But on Z, the call instruction doesn't touch the stack (the called function might, but it also might not, so we cannot really rely on it).

removed

Merged remaining X86 "small/medium/large" into stack-clash-protection.ll.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D78717/new/

https://reviews.llvm.org/D78717

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/Basic/Targets/SystemZ.h
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/test/CodeGen/stack-clash-protection.c
  clang/test/Driver/stack-clash-protection-02.c
  llvm/include/llvm/ADT/Triple.h
  llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
  llvm/lib/Target/SystemZ/SystemZFrameLowering.h
  llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
  llvm/lib/Target/SystemZ/SystemZISelLowering.h
  llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
  llvm/lib/Target/SystemZ/SystemZInstrInfo.h
  llvm/lib/Target/SystemZ/SystemZInstrInfo.td
  llvm/lib/Target/SystemZ/SystemZOperators.td
  llvm/test/CodeGen/SystemZ/stack-clash-dynamic-alloca.ll
  llvm/test/CodeGen/SystemZ/stack-clash-protection.ll

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