[llvm-bugs] [Bug 38683] New: [NewGVN] Running NewGVN twice back-to-back discovers additional equivalences

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=38683

            Bug ID: 38683
           Summary: [NewGVN] Running NewGVN twice back-to-back discovers
                    additional equivalences
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: Florian.Hahn at arm.com
                CC: llvm-bugs at lists.llvm.org

running `opt -newgvn -newgvn` on the code below eliminates %bf.set.1 and
%bf.clear.1, but `opt -newgvn` does not.


@a = external global i64

define void @fn1(i1 %bc) {
entry:
  br label %for.cond

for.cond:                                         ; preds = %for.cond1.1,
%entry
  %tmp = phi i1 [ 1, %entry ], [ 1, %for.cond ]
  %conv = zext i1 %tmp to i32
  %lv = load i32, i32* bitcast (i64* @a to i32*)
  %bf.clear = and i32 %lv, -131072
  %bf.set = or i32 %conv, %bf.clear
  %bf.clear.1 = and i32 %bf.set, -131072
  %bf.set.1 = or i32 1, %bf.clear.1
  br i1 %bc, label %for.cond, label %exit

exit:                              ; preds = %for.cond1
  store i32 %bf.set.1, i32* bitcast (i64* @a to i32*)
  ret void
}

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