[PATCH] D139275: [SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

  -- 49. InstCombinePass
  
  ----------------------------------------
  define float @_Z1ff(float noundef %0) nofree noundef willreturn memory(none) {
  %1:
    %2 = fcmp ugt float noundef %0, 0.000000
    %3 = fcmp ult float noundef %0, 1.000000
    %or.cond = and i1 %2, %3
    %4 = fcmp uge float noundef %0, 0.200000
    %5 = xor i1 %2, %or.cond
    %.0.sel6 = select i1 %5, float 0.100000, float 0.000000
    %or.cond7 = and i1 %4, %or.cond
    %6 = fadd float noundef %0, -0.100000
    %.0 = select i1 %or.cond7, float %6, float %.0.sel6
    ret float %.0
  }
  =>
  define float @_Z1ff(float noundef %0) nofree noundef willreturn memory(none) {
  %1:
    %2 = fcmp ugt float noundef %0, 0.000000
    %3 = fcmp ult float noundef %0, 1.000000
    %or.cond = and i1 %2, %3
    %4 = fcmp uge float noundef %0, 0.200000
    %5 = fadd float noundef %0, -0.100000
    %.0.sel6 = select i1 %4, float %5, float 0.100000
    %.0 = select i1 %or.cond, float %.0.sel6, float 0.000000
    ret float %.0
  }
  Transformation doesn't verify! (unsound)
  ERROR: Value mismatch
  
  Example:
  float noundef %0 = #x7f800000 (+oo)
  
  Source:
  i1 %2 = #x1 (1)
  i1 %3 = #x0 (0)
  i1 %or.cond = #x0 (0)
  i1 %4 = #x1 (1)
  i1 %5 = #x1 (1)
  float %.0.sel6 = #x3dcccccd (0.100000001490?)
  i1 %or.cond7 = #x0 (0)
  float %6 = #x7f800000 (+oo)
  float %.0 = #x3dcccccd (0.100000001490?)
  
  Target:
  i1 %2 = #x1 (1)
  i1 %3 = #x0 (0)
  i1 %or.cond = #x0 (0)
  i1 %4 = #x1 (1)
  float %5 = #x7f800000 (+oo)
  float %.0.sel6 = #x7f800000 (+oo)
  float %.0 = #x00000000 (+0.0)
  Source value: #x3dcccccd (0.100000001490?)
  Target value: #x00000000 (+0.0)
  
  Pass: InstCombinePass
  Command line: '/builddirs/llvm-project/build-Clang15/bin/opt' '-load=/repositories/alive2/build-Clang-release/tv/tv.so' '-load-pass-plugin=/repositories/alive2/build-Clang-release/tv/tv.so' '-tv-exit-on-error' '-O1' '/tmp/test.ll' '-tv-smt-to=20000' '-tv-report-dir=/repositories/alive2/build-Clang-release/logs' '-tv-smt-stats'


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D139275/new/

https://reviews.llvm.org/D139275