[all-commits] [llvm/llvm-project] e43143: InstCombine: Fold bitcast of vector with constant ...

[Matt Arsenault via All-commits]

  Branch: refs/heads/users/arsenm/instcombine/fold-bitcast-through-select-const-vector
  Home:   https://github.com/llvm/llvm-project
  Commit: e43143c86823916df7788db16553a195a11bce42
      https://github.com/llvm/llvm-project/commit/e43143c86823916df7788db16553a195a11bce42
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2026-02-19 (Thu, 19 Feb 2026)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
    A llvm/test/Transforms/InstCombine/bitcast-select-const-vector.ll
    M llvm/test/Transforms/InstCombine/copysign.ll
    M llvm/test/Transforms/InstCombine/fold-bin-operand.ll

  Log Message:
  -----------
  InstCombine: Fold bitcast of vector with constant to scalar

Fold bitcast (select cond, val, const) ->
  select cond, (bitcast val), (bitcast const)

Rocm device libs has an unfortunate amount of code that does bithacking
on the sign bit of double values by casting to <2 x i32> and operation
on the high element. This breaks value tracking optimizations on the
fp value.

The existing transform would only do this if the input to the select was
also a bitcast with a single use, and if it didn't convert between vector
and scalar.


  Commit: c6126562081c155b9f0ac4e5935c2442023a95f3
      https://github.com/llvm/llvm-project/commit/c6126562081c155b9f0ac4e5935c2442023a95f3
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2026-02-19 (Thu, 19 Feb 2026)

  Changed paths:
    M llvm/test/Transforms/InstCombine/bitcast-select-const-vector.ll

  Log Message:
  -----------
  Add negative vselect test


  Commit: ae7d28c7106b2c93d98be2479baf0440380c9aa8
      https://github.com/llvm/llvm-project/commit/ae7d28c7106b2c93d98be2479baf0440380c9aa8
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2026-02-19 (Thu, 19 Feb 2026)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
    M llvm/test/Transforms/InstCombine/bitcast-select-const-vector.ll

  Log Message:
  -----------
  Restrict to not introduce select of vector

Allow reducing the number of vector elements, but
not increase.


Compare: https://github.com/llvm/llvm-project/compare/fd146bef1b1a...ae7d28c7106b

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