[llvm-bugs] [Bug 47486] New: Unreported changes from rewriteLoopExitValues

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47486

            Bug ID: 47486
           Summary: Unreported changes from rewriteLoopExitValues
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Transformation Utilities
          Assignee: unassignedbugs at nondot.org
          Reporter: dmajor at mozilla.com
                CC: lebedev.ri at gmail.com, llvm-bugs at lists.llvm.org,
                    sguelton at redhat.com

Created attachment 23946
  --> https://bugs.llvm.org/attachment.cgi?id=23946&action=edit
SwitchLoweringUtils.ll

With expensive checks enabled:
$ opt -indvars -S SwitchLoweringUtils.ll
Pass modifies its input and doesn't report it: Induction Variable
Simplification

With some early returns in IndVarSimplify.cpp, I narrowed it down to
rewriteLoopExitValues, but I'm not sure about the specific line.

It's unclear if bugpoint did something bad here: the only predecessor of the
`ret` is the first instruction, so everything in between is an infinite loop. I
can share the original repro if that's better.

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