[llvm-bugs] [Bug 49873] New: NewGVN miscompile and crash

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49873

            Bug ID: 49873
           Summary: NewGVN miscompile and crash
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: ruiling.song83 at gmail.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 24727
  --> https://bugs.llvm.org/attachment.cgi?id=24727&action=edit
IR reproducer

NewGVN fails to add extra dependency when processing an icmp with one operand
being phi-node. it tries to evaluate a phi-of-icmp and later one of the icmp
proved to be constant based on a previous predicate, see the code after big
piece of comment in NewGVN::performSymbolicCmpEvaluation(). We need to make
sure the dependency between the real instruction and the predicate condition
was added.
opt -S -newgvn -o - reproduce.ll

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