[all-commits] [llvm/llvm-project] 488875: [X86] Fix crash on BT bit index narrower than log2...

[Paweł Bylica via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 488875cedfbea669afa93298a0a98594c1a9cb92
      https://github.com/llvm/llvm-project/commit/488875cedfbea669afa93298a0a98594c1a9cb92
  Author: Paweł Bylica <pawel at hepcolgum.band>
  Date:   2026-06-06 (Sat, 06 Jun 2026)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/bt-merge-fuse.ll

  Log Message:
  -----------
  [X86] Fix crash on BT bit index narrower than log2(BW) (#201793)

peekThroughBitPosExtTrunc asserted that peeling
TRUNCATE/ZERO_EXTEND/ANY_EXTEND never drops below log2(BW) bits, but a
BT bit index can be e.g. a zext of i1. Stop peeking there instead: below
log2(BW) bits a peeled value no longer determines the bit index on its
own, so comparing peeled values would also be unsound.

Fixes #201444.



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