[all-commits] [llvm/llvm-project] bc2004: [RISCV] Handle LHS == 0 in isVLKnownLE (#148860)

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bc2004c2e42f633ee4099ea5652df41dba29c79c
      https://github.com/llvm/llvm-project/commit/bc2004c2e42f633ee4099ea5652df41dba29c79c
  Author: Luke Lau <luke at igalia.com>
  Date:   2025-07-16 (Wed, 16 Jul 2025)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vsadd-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vsaddu-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vssub-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vssubu-vp.ll

  Log Message:
  -----------
  [RISCV] Handle LHS == 0 in isVLKnownLE (#148860)

If a VL is zero then it's known to be less than or equal to every other
VL.

This looks weird on its own since a VL of zero isn't that common. The
test diffs come from a type being split resulting in a VP intrinsic's
EVL being zero.

The motivation for this is to split off part of an upcoming patch I plan
on submitting for RISCVVLOptimizer, which generalizes it to handle
recurrences, and needs to reason about an initial state of demanded VLs
set to zero.



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