[all-commits] [llvm/llvm-project] a498e6: [LV] Cost EVL width-adjusting zext/trunc as free (...

[Pengcheng Wang via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a498e642af4aded70fd48bda68b0692a58425e86
      https://github.com/llvm/llvm-project/commit/a498e642af4aded70fd48bda68b0692a58425e86
  Author: Pengcheng Wang <wangpengcheng.pp at bytedance.com>
  Date:   2026-09-24 (Thu, 24 Sep 2026)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h
    M llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
    M llvm/test/Transforms/LoopVectorize/RISCV/force-vect-msg.ll
    M llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-cost.ll

  Log Message:
  -----------
  [LV] Cost EVL width-adjusting zext/trunc as free (#225016)

With EVL tail folding, the scalar zext/trunc that adjusts the i32
ExplicitVectorLength to the canonical IV type was priced as a regular
cast (cost 1). It never lowers to an instruction, only feeding the
(free) IV increment and AVL decrement, so the phantom cost dropped
borderline loops such as TSVC s351 on RV64 to VF 1.

Here we return 0 for such casts so that we don't over-estimate the
cost.

Fixes #224987

Assisted-by: TRAE CLI (Opus 4.8)



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