[all-commits] [llvm/llvm-project] a849f5: [InstCombine] Fix assertion failure in `foldVariab...

[rdevshp via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a849f52b7930ead34ce6337763cff9977f5f61aa
      https://github.com/llvm/llvm-project/commit/a849f52b7930ead34ce6337763cff9977f5f61aa
  Author: rdevshp <rdevshp at gmail.com>
  Date:   2026-07-07 (Tue, 07 Jul 2026)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
    M llvm/test/Transforms/InstCombine/conditional-variable-length-signext-after-high-bit-extract.ll

  Log Message:
  -----------
  [InstCombine] Fix assertion failure in `foldVariableSignZeroExtensionOfVariableHighBitExtract` (#205148)

This PR fixes crash for the following program:
```
define i16 @d(i16 %x, i4 %n) {
entry:
  %highbits = lshr i16 %x, 1
  %sub1 = sub i4 0, %n
  %z1 = zext i4 %sub1 to i16
  %shl = shl i16 %highbits, %z1
  %sub2 = sub i4 0, %n
  %z2 = zext i4 %sub2 to i16
  %ashr = ashr i16 %shl, %z2
  ret i16 %ashr
}
```
when running `opt -passes=instcombine prog.ll -S`.

Assisted-by: Codex



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