[llvm-bugs] [Bug 47769] New: ScalarEvolution can introduce branch on poison

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47769

            Bug ID: 47769
           Summary: ScalarEvolution can introduce branch on poison
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: kevindevos9542 at gmail.com
                CC: chenzheng1030 at hotmail.com, florian_hahn at apple.com,
                    huihuiz at codeaurora.org, lebedev.ri at gmail.com,
                    llvm-bugs at lists.llvm.org, max.kazantsev at azul.com,
                    nunoplopes at sapo.pt, sam.parker at arm.com

Test: Transforms/LoopVectorize/pr30654-phiscev-sext-trunc.ll
Function: doit1
Reason: Source more defined than target

Example: https://godbolt.org/z/1nMsMT
LoopVectorize adds the block vector.scevcheck and uses SCEVExpander to generate
checks that use %step. If %step is poison it introduces branch on poison.

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