[all-commits] [llvm/llvm-project] 620ad7: [InstCombine] Match swapped form of truncating sat...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 620ad7e90ade5051e34410496ab2a241223d28a6
      https://github.com/llvm/llvm-project/commit/620ad7e90ade5051e34410496ab2a241223d28a6
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2026-09-28 (Mon, 28 Sep 2026)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
    M llvm/test/Transforms/InstCombine/truncating-saturate.ll

  Log Message:
  -----------
  [InstCombine] Match swapped form of truncating saturation clamp (#226614)

Extend the fold added in #189703 to also handle the inverted select:
trunc (select (icmp ugt A, DestTy_umax), sext(icmp sgt A, 0), A) -->
trunc (smin (smax (0, A), DestTy_umax))

InstCombine canonicalizes (A & NegPow2) != 0 into the ult form with
swapped select operands, but if SCCP first rewrites the compare as
icmp uge A, C, InstCombine only turns it into icmp ugt and never swaps
the select, so the original fold is missed.

While here, match the compare constant with m_APInt instead of
m_Constant + getUniqueInteger, and build TruncatedMax directly with
APInt::getLowBitsSet. Comparing the constant against TruncatedMax + 1
or TruncatedMax makes the separate zero check unnecessary.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply at anthropic.com>



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications