[llvm-bugs] [Bug 26574] New: Function replaceCongruentIVs can crash if incoming phi value is a global variable

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=26574

            Bug ID: 26574
           Summary: Function replaceCongruentIVs can crash if incoming phi
                    value is a global variable
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: mattias.v.eriksson at ericsson.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 15882
  --> https://llvm.org/bugs/attachment.cgi?id=15882&action=edit
Reduced input file with crash in indvars

I found this crash in one of our internal test suites and reduced it to the
attached repr.ll.

opt -S -indvars repr.ll

crashes like this:

opt: ../include/llvm/Support/Casting.h:237: typename cast_retty<X, Y
*>::ret_type llvm::cast(Y *) [X = llvm::Instruction, Y = llvm::Value]:
Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.


Called from this line in ScalarEvolutionExpander.cpp:
      Instruction *OrigInc =
        cast<Instruction>(OrigPhiRef->getIncomingValueForBlock(LatchBlock));

(gdb) p OrigPhiRef->dump()
  %_tmp19 = phi i16** [ @pglob, %bb_lslct36 ], [ %_tmp196, %bb2 ]

pglob is a "external global i16*" here.

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