[all-commits] [llvm/llvm-project] da65d6: [KnownFPClass] Fix canonicalize incorrectly droppi...

[lijinpei-amd via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: da65d6afe74463745dae9af0ce47f31e4186778e
      https://github.com/llvm/llvm-project/commit/da65d6afe74463745dae9af0ce47f31e4186778e
  Author: lijinpei-amd <jinpli at amd.com>
  Date:   2026-06-12 (Fri, 12 Jun 2026)

  Changed paths:
    M llvm/lib/Support/KnownFPClass.cpp
    M llvm/test/Transforms/Attributor/nofpclass-canonicalize.ll
    M llvm/test/Transforms/InstCombine/simplify-demanded-fpclass-canonicalize.ll

  Log Message:
  -----------
  [KnownFPClass] Fix canonicalize incorrectly dropping fcNegZero under positive-zero denormal mode (#202268)

The denormal mode only flushes *denormal* (subnormal) values; -0.0 is
not a denormal, and per LangRef canonicalize must conserve the sign of
zero (canonicalize(-0.0) == -0.0).

Alive2 (InstCombine fold of canonicalize on a {+/-0, nan} value):
  before (miscompiles -0.0 -> +0.0): https://alive2.llvm.org/ce/z/ZRK-sr
  after  (verifies):                 https://alive2.llvm.org/ce/z/L3tPu3



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