[LLVMbugs] [Bug 19753] New: InstCombine: constant comparison involving "ashr exact" not optimized well

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=19753

            Bug ID: 19753
           Summary: InstCombine: constant comparison involving "ashr
                    exact" not optimized well
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: david.majnemer at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

consider:
define i1 @exact_ashr_eq_false(i32 %a) {
  %shr = ashr exact i32 -30, %a
  %cmp = icmp eq i32 %shr, -15
  ret i1 %cmp
}

I think this should just be:
define i1 @exact_ashr_eq_false(i32 %a) {
  %cmp = icmp eq i32 %a, 1
  ret i1 %cmp
}

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