[llvm-bugs] [Bug 34023] New: Large amount of time taken in ScalarEvolution

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34023

            Bug ID: 34023
           Summary: Large amount of time taken in ScalarEvolution
           Product: libraries
           Version: 5.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: alex at crichton.co
                CC: llvm-bugs at lists.llvm.org

Originally reported at https://github.com/rust-lang/rust/issues/43418, we got a
reduced test case in Rust and I used `bugpoint` to reduce that even further to
yield a wad of IR located at
https://gist.github.com/alexcrichton/22bc33959863bf43169fe2776c227db4

If that IR (relatively small) is compiled with:

    llc -O1 -filetype=obj foo.ll -o foo.o

it takes ~30s locally on my machine (the timeout I passed to `bugpoint`). The
original test case (which I can also get the IR if if you'd like) took much
much longer, but presumably may have exited at some point!

Also not I'm not entirely ertain that this is in ScalarEvolution, so please
feel free to retitle the bug!

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