[llvm-bugs] [Bug 41057] New: [X86] __builtin_rotateright* does not use rotate by 1 instructions or rorx with bmi

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41057

            Bug ID: 41057
           Summary: [X86] __builtin_rotateright* does not use rotate by 1
                    instructions or rorx with bmi
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: craig.topper at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

The isel patterns for rotates by immediates are written assuming rotate by
immediate will always use a rotl operation because that's what the pattern
matching code from the shift+or pattern will do.

But the __builtin_rotateright* functions use the funnel shift intrinsics and
will be turned directly into rotr by SelectionDAGBuilder. This will miss most
of the patterns except the ror by immediate patterns.

Godbolt example showing both issues https://godbolt.org/z/7Tt1ki

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