[llvm-bugs] [Bug 47949] New: CTPOP(x) > 0 isn't optimized away before SelectionDAG?

via llvm-bugs llvm-bugs at lists.llvm.org
Thu Oct 22 11:34:09 PDT 2020


            Bug ID: 47949
           Summary: CTPOP(x) > 0 isn't optimized away before SelectionDAG?
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: dave at znu.io
                CC: llvm-bugs at lists.llvm.org

I committed exhaustive x86 CTPOP tests to the repo this morning

Notably, unsigned greater-than-zero tests are generating actual CTPOP emulation
when they don't need to. It should just optimize down to a comparison against

My limited investigation shows that SelectionDAG can fix this, but shouldn't an
earlier pass have caught this?

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