[LLVMbugs] [Bug 22005] New: GVN can't remove trivially identical operations in zlib

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22005

            Bug ID: 22005
           Summary: GVN can't remove trivially identical operations in
                    zlib
           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:
target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

define i64 @f(i8* %out, i8* %end) {
  %1 = icmp ult i8* %out, %end
  br i1 %1, label %2, label %6

; <label>:2                                       ; preds = %0
  %3 = ptrtoint i8* %end to i64
  %4 = ptrtoint i8* %out to i64
  %5 = sub i64 %3, %4
  br label %10

; <label>:6                                       ; preds = %0
  %7 = ptrtoint i8* %out to i64
  %8 = ptrtoint i8* %end to i64
  %9 = sub i64 %8, %7
  br label %10

; <label>:10                                      ; preds = %6, %2
  %.in = phi i64 [ %5, %2 ], [ %9, %6 ]
  %11 = add i64 %.in, 257
  ret i64 %11
}

both sub operations are computing end-out

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