[PATCH] D124530: [X86] Fix gather/scatter with large scales (PR55021)

[Nikita Popov via Phabricator via llvm-commits]

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The AVX512 gather/scatter instructions only support scales up to 8. If the scale is larger, perform an explicit shift operation instead.

I'm not familiar with the requirements for the instruction -- is a scale that does not match the scatter element width actually supported? The instruction looks sensible, but I don't know if this is actually legal. If not, the check could be change to compare with the element width.

Fixes https://github.com/llvm/llvm-project/issues/55021.


https://reviews.llvm.org/D124530

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/gather-scatter-opaque-ptr.ll

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