[PATCH] D153846: [SelectionDAG] do not fold (sext i32 undef to i64) to 0

[Mohammed Nurul Hoque via Phabricator via llvm-commits]

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When sign-extending i32 undef to i64, previously it was folded to 0. Replace with i64 undef. This eliminates instructions that set undefined ABI registers to 0


https://reviews.llvm.org/D153846

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/test/CodeGen/AArch64/abd-combine.ll
  llvm/test/CodeGen/AArch64/hadd-combine.ll
  llvm/test/CodeGen/AArch64/neon-dotreduce.ll
  llvm/test/CodeGen/PowerPC/p10-spill-crun.ll
  llvm/test/CodeGen/RISCV/miss-sp-restore-eh.ll
  llvm/test/CodeGen/RISCV/pr51206.ll
  llvm/test/CodeGen/RISCV/sext-zext-trunc.ll
  llvm/test/CodeGen/X86/vector-shuffle-v1.ll

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