[llvm-bugs] [Bug 46118] New: Large numbers of (e.g., 27) redundant vxorpd generated on loop entry

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46118

            Bug ID: 46118
           Summary: Large numbers of (e.g., 27) redundant vxorpd generated
                    on loop entry
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: elrodc at gmail.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

The generated code does the following:
vxorp 27 registers
checks if the loop iterates at least once. If it doesn't, jump.
vxorp those exact same 27 registers
enters loop.

The second set of 27 vxorpd is unnecessary, those registers are all already 0.

Godbolt:
https://godbolt.org/z/nsc7kc

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