[PATCH] D131158: [SystemZ] Improve handling of vector alignments

[Jonas Paulsson via Phabricator via llvm-commits]

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With these first experiments, I see:

- Clang seems to now emit a padding in the case of no-vx, like

  %struct.S = type { i32, [12 x i8], <4 x i32> }

instead of

  %struct.S = type { i32, <4 x i32> }

This should be equivalent, in the final output, I would hope, although I have not looked into that handling in detail.

- As seen in function-attributes-01.ll, if the IR has no alignment specified, it is 8-byte aligned now even with -vector.

- vec-abi-align.ll needed updating to include the padding in the struct - as now expected from clang - to work...

It seems that SPEC builds identically both for z15 and zEC12, which is promising. I however don't quite know if this is actually correct or not: what if some optimizer want to build a vector and adds the wrong alignment in the no-vx case? Is the alignment as specified by the front end and found in the I/R enough to make this work in all cases? I am a little worried that some optimizer might look up that alignment value in DataLayout and use that instead...


https://reviews.llvm.org/D131158

Files:
  clang/lib/Basic/Targets/SystemZ.h
  clang/test/CodeGen/SystemZ/align-systemz-02.c
  clang/test/CodeGen/target-data.c
  llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
  llvm/test/CodeGen/SystemZ/function-attributes-01.ll
  llvm/test/CodeGen/SystemZ/vec-abi-align.ll

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