[PATCH] D74453: [LegalizeTypes][RISCV] Correctly sign-extend comparison for ATOMIC_CMP_XCHG

[James Clarke via Phabricator via llvm-commits]

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Currently, the comparison argument used for ATOMIC_CMP_XCHG is legalised
with GetPromotedInteger, which leaves the upper bits of the value
undefind. Since this is used for comparing in an LR/SC loop with a
full-width comparison, we must sign extend it. We introduce a new
getExtendForAtomicCmpSwapArg to complement getExtendForAtomicOps, since
many targets have compare-and-swap instructions (or pseudos) that
correctly handle an any-extend input, and the existing function
determines the extension of the result, whereas we are concerned with
the input.

This is related to https://reviews.llvm.org/D58829, which solved the
issue for ATOMIC_CMP_SWAP_WITH_SUCCESS, but not the simpler
ATOMIC_CMP_SWAP.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74453

Files:
  llvm/include/llvm/CodeGen/TargetLowering.h
  llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
  llvm/lib/Target/RISCV/RISCVISelLowering.h
  llvm/test/CodeGen/RISCV/atomic-cmpxchg.ll
  llvm/test/CodeGen/RISCV/atomic-rmw.ll

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