[llvm-bugs] [Bug 47922] New: Suboptimal lowering of conditional binop identity

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47922

            Bug ID: 47922
           Summary: Suboptimal lowering of conditional binop identity
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: laytonkifer at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, pengfei.wang at intel.com,
                    spatel+llvm at rotateright.com

The x86 backend fails to notice when expanding selects/phis will cause things
like addition of 0 and emits unnecessary instructions.

examples: https://godbolt.org/z/j5onGK

I would potentially be interested in looking into this, but I am fairly new to
LLVM. This would be my first time working on one of the backends. If anyone
could point me in the right direction as to where to begin, that would be
great.

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