[all-commits] [llvm/llvm-project] 0a913b: [X86] Fold some (truncate (srl (add X, C1), C2)) p...

[João Gouveia via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0a913b5e3a234d3261ccca54f9458715c00fae3b
      https://github.com/llvm/llvm-project/commit/0a913b5e3a234d3261ccca54f9458715c00fae3b
  Author: João Gouveia <jtalonegouveia at gmail.com>
  Date:   2025-02-21 (Fri, 21 Feb 2025)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    A llvm/test/CodeGen/X86/combine-i64-trunc-srl-add.ll

  Log Message:
  -----------
  [X86] Fold some (truncate (srl (add X, C1), C2)) patterns to (add (truncate (srl X, C2)), C1') (#126448)

Addresses the poor codegen identified in #123239 and a few extra cases.
This transformation is correct for `eq`
(https://alive2.llvm.org/ce/z/qZhwtT), `ne`
(https://alive2.llvm.org/ce/z/6gsmNz), `ult`
(https://alive2.llvm.org/ce/z/xip_td) and `ugt`
(https://alive2.llvm.org/ce/z/39XQkX).

Fixes #123239



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