[all-commits] [llvm/llvm-project] 1bd0b8: [SimplifyCFG] `FoldBranchToCommonDest()`: deal wit...

[Roman Lebedev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1bd0b82e508d049efdb07f4f8a342f35818df341
      https://github.com/llvm/llvm-project/commit/1bd0b82e508d049efdb07f4f8a342f35818df341
  Author: Roman Lebedev <lebedev.ri at gmail.com>
  Date:   2022-12-12 (Mon, 12 Dec 2022)

  Changed paths:
    M llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    M llvm/test/CodeGen/AArch64/rm_redundant_cmp.ll
    M llvm/test/CodeGen/AArch64/tailmerging_in_mbp.ll
    M llvm/test/CodeGen/AArch64/typepromotion-cost.ll
    M llvm/test/CodeGen/PowerPC/ppc-ctr-dead-code.ll
    M llvm/test/CodeGen/PowerPC/pr48527.ll
    M llvm/test/CodeGen/X86/loop-search.ll
    M llvm/test/Transforms/InstCombine/unused-nonnull.ll
    M llvm/test/Transforms/LICM/hoist-phi.ll
    M llvm/test/Transforms/LICM/sinking.ll
    M llvm/test/Transforms/LoopStrengthReduce/AArch64/small-constant.ll
    M llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
    M llvm/test/Transforms/LoopUnroll/scevunroll.ll
    M llvm/test/Transforms/LoopUnroll/unroll-after-peel.ll
    M llvm/test/Transforms/LoopUnroll/unroll-header-exiting-with-phis-multiple-exiting-blocks.ll
    M llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
    M llvm/test/Transforms/SimplifyCFG/X86/SpeculativeExec.ll
    M llvm/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
    M llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest-phis.ll
    M llvm/test/Transforms/SimplifyCFG/fold-branch-to-common-dest.ll
    M llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue.ll
    M llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll

  Log Message:
  -----------
  [SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block

This tries to approach the problem noted by @arsenm:
terrible codegen for `__builtin_fpclassify()`:
https://godbolt.org/z/388zqdE37

Just because the PHI in the common successor happens to have different
incoming values for these two blocks, doesn't mean we have to give up.
It's quite easy to deal with this, we just need to produce a select:
https://alive2.llvm.org/ce/z/000srb

Now, the cost model for this transform is rather overly strict,
so this will basically never fire. We tally all (over all preds)
the selects needed to the NumBonusInsts

Differential Revision: https://reviews.llvm.org/D139275


  Commit: 73472b6ee76aba9d487eddc5d51a71de3d7cddb8
      https://github.com/llvm/llvm-project/commit/73472b6ee76aba9d487eddc5d51a71de3d7cddb8
  Author: Roman Lebedev <lebedev.ri at gmail.com>
  Date:   2022-12-12 (Mon, 12 Dec 2022)

  Changed paths:
    M llvm/test/Other/opt-legacy-syntax-deprecation.ll
    R llvm/test/Other/opt-old-new-pm-passes.ll
    M llvm/tools/opt/opt.cpp

  Log Message:
  -----------
  [opt] NewPM: `opt -passname` syntax is dead, long live `opt -passes=<pipeline>`!

I've done final pass, and there are no more tests to update.
All other tests (=codegen tests) are using old pass manager.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D139677


Compare: https://github.com/llvm/llvm-project/compare/647d314eb059...73472b6ee76a