[all-commits] [llvm/llvm-project] e80da0: [RISCV] Disable combineBinOpToReduce if the reduct...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e80da0f8409aaf70d18b12c5d5d884f2c9cbddcc
      https://github.com/llvm/llvm-project/commit/e80da0f8409aaf70d18b12c5d5d884f2c9cbddcc
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2023-04-25 (Tue, 25 Apr 2023)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp

  Log Message:
  -----------
  [RISCV] Disable combineBinOpToReduce if the reduction AVL might be 0.

If the reduction AVL is 0, operand 0 of the reduction will be
returned rather than the scalar input.

To make the fold legal, we would need to fold the new scalar value
with whatever operand 0 is which may require a new scalar operation
before the reduction.

Block the combine if we can't prove AVL is non-zero.

Reviewed By: fakepaper56

Differential Revision: https://reviews.llvm.org/D149174