[PATCH] D82005: [InstCombine] Replace selects with Phis

[Mikael Holmén via Phabricator via llvm-commits]

uabelho added a comment.

Hi,

We've noticed a crash that started occuring with this patch.
Running

  opt -S -o - bbi-50827.ll -instcombine

results in

  opt: ../include/llvm/ADT/DenseMap.h:1241: llvm::DenseMapIterator::pointer llvm::DenseMapIterator<llvm::BasicBlock *, std::unique_ptr<llvm::DomTreeNodeBase<llvm::BasicBlock>, std::default_delete<llvm::DomTreeNodeBase<llvm::BasicBlock> > >, llvm::DenseMapInfo<llvm::BasicBlock *>, llvm::detail::DenseMapPair<llvm::BasicBlock *, std::unique_ptr<llvm::DomTreeNodeBase<llvm::BasicBlock>, std::default_delete<llvm::DomTreeNodeBase<llvm::BasicBlock> > > >, true>::operator->() const [KeyT = llvm::BasicBlock *, ValueT = std::unique_ptr<llvm::DomTreeNodeBase<llvm::BasicBlock>, std::default_delete<llvm::DomTreeNodeBase<llvm::BasicBlock> > >, KeyInfoT = llvm::DenseMapInfo<llvm::BasicBlock *>, Bucket = llvm::detail::DenseMapPair<llvm::BasicBlock *, std::unique_ptr<llvm::DomTreeNodeBase<llvm::BasicBlock>, std::default_delete<llvm::DomTreeNodeBase<llvm::BasicBlock> > > >, IsConst = true]: Assertion `Ptr != End && "dereferencing end() iterator"' failed.
  PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.

with bbi-50827.ll being

  @a = external global i1, align 1
  
  define i16 @g()  {
  entry:
    %.b = load i1, i1* @a, align 1
    %0 = select i1 %.b, i16 0, i16 5
    br label %for.body.i
  
  for.body.i:                                       ; preds = %for.body.i, %entry
    br label %for.body.i
  
  f.exit:                                           ; No predecessors!
    ret i16 %0
  }

Note the use of %0 in f.exit, which is not reachable from entry.


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https://reviews.llvm.org/D82005