[llvm-bugs] [Bug 44427] New: [InstCombine] sub (and %x, -16), %x -> 0-(and %x, 15)

via llvm-bugs llvm-bugs at lists.llvm.org
Wed Jan 1 13:33:19 PST 2020


            Bug ID: 44427
           Summary: [InstCombine] sub (and %x, -16), %x -> 0-(and %x, 15)
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: llvm-bugs at lists.llvm.org

Looks like missed canonicalization to me. Not sure how much matters overall.

Name: sub (and %x, -16), %x -> 0-(and %x, 15)
Pre: isPowerOf2OrZero(-C1)
  %o = and i64 %x, C1
  %r = sub i64 %o, %x
  %n = and i64 %x, (-C1-1)
  %r = sub i64 0, %n


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