[all-commits] [llvm/llvm-project] 10da98: [LSR] Drop LSR solution if it is less profitable t...

[Yueh-Ting (eop) Chen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 10da9844d072df41d3eeeb6f104e2160fc7a2193
      https://github.com/llvm/llvm-project/commit/10da9844d072df41d3eeeb6f104e2160fc7a2193
  Author: eopXD <yueh.ting.chen at gmail.com>
  Date:   2022-10-27 (Thu, 27 Oct 2022)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
    A llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution-dbg-msg.ll
    M llvm/test/Transforms/LoopStrengthReduce/RISCV/lsr-drop-solution.ll

  Log Message:
  -----------
  [LSR] Drop LSR solution if it is less profitable than baseline

The LSR may suggest less profitable transformation to the loop. This
patch adds check to prevent LSR from generating worse code than what
we already have.

Since LSR affects nearly all targets, the patch is guarded by the
option 'lsr-drop-solution' and default as disable for now.

The next step should be extending an TTI interface to allow target(s)
to enable this enhancememnt.

Debug log is added to remind user of such choice to skip the LSR
solution.

Reviewed By: Meinersbur, #loopoptwg

Differential Revision: https://reviews.llvm.org/D126043