[llvm-bugs] [Bug 37951] New: error: use of undefined value '%.split.split.split.[...].split.spl171 with "-bounds-checking -aggressive-instcombine -loop-unswitch -loop-rotate -licm -sroa -simple-loop-unswitch"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37951

            Bug ID: 37951
           Summary: error: use of undefined value
                    '%.split.split.split.[...].split.spl171 with
                    "-bounds-checking -aggressive-instcombine
                    -loop-unswitch -loop-rotate -licm -sroa
                    -simple-loop-unswitch"
           Product: new-bugs
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: mikael.holmen at ericsson.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 20472
  --> https://bugs.llvm.org/attachment.cgi?id=20472&action=edit
reproducer

Running

 opt -S -o - bbi-15719.ll -bounds-checking -aggressive-instcombine
-loop-unswitch -loop-rotate -licm -sroa -simple-loop-unswitch | opt -S

gives

opt: <stdin>:1729:29: error: use of undefined value
'%.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.spl171'
  %a.1.0 = phi i16 [ undef,
%.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.split.spl171
], [ %_tmp548, %bb1 ]

Looking at the output from the first opt invocation there is indeed a use of
the mentioned basic block at line 1729 that
isn't defined anywhere.

What's funny though is that this isn't caught by the verifier, so just doing

 opt -S -o - bbi-15719.ll -bounds-checking -aggressive-instcombine
-loop-unswitch -loop-rotate -licm -sroa -simple-loop-unswitch - verify-each

passes.

Found during fuzz testing with random passes on random input.

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