[all-commits] [llvm/llvm-project] 230c8c: [Reassociate] Cleanup minor missed optimizations

[wjristow via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 230c8c56f21cfe4e23a24793f3137add1af1d1f0
      https://github.com/llvm/llvm-project/commit/230c8c56f21cfe4e23a24793f3137add1af1d1f0
  Author: Warren Ristow <warren.ristow at sony.com>
  Date:   2022-07-14 (Thu, 14 Jul 2022)

  Changed paths:
    M llvm/lib/Transforms/Scalar/Reassociate.cpp
    M llvm/test/Transforms/Reassociate/fast-ReassociateVector.ll
    M llvm/test/Transforms/Reassociate/fast-basictest.ll
    M llvm/test/Transforms/Reassociate/pr42349.ll

  Log Message:
  -----------
  [Reassociate] Cleanup minor missed optimizations

In analyzing issue #56483, it was noticed that running `opt` with
`-reassociate` was missing some minor optimizations. For example,
there were cases where the running `opt` on IR with floating-point
instructions that have the `fast` flags applied, sometimes resulted in
less efficient code than the input IR (things like dead instructions
left behind, and missed reassociations). These were sometimes noted
in the test-files with TODOs, to investigate further. This commit
fixes some of these problems, removing some TODOs in the process.

FTR, I refer to these as "minor" missed optimizations, because when
running a full clang/llvm compilation, these inefficiencies are not
happening, as other passes clean that residue up. Regardless, having
cleaner IR produced by `opt`, makes assessing the quality of fixes done
in `opt` easier.