[llvm-bugs] [Bug 52546] New: [InstSimplify] missed X==0 fold of bool value

via llvm-bugs llvm-bugs at lists.llvm.org
Thu Nov 18 07:06:33 PST 2021


            Bug ID: 52546
           Summary: [InstSimplify] missed X==0 fold of bool value
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: spatel+llvm at rotateright.com
                CC: llvm-bugs at lists.llvm.org

Forking this off from bug 52543 :

define i1 @src(i1 %b) {
  %not = xor i1 %b, true
  %s = sext i1 %not to i32
  %cmp = icmp eq i32 %s, 0
  ret i1 %cmp

define i1 @tgt(i1 %b) {
  ret i1 %b

Note that "opt -instcombine" gets this example, and "opt -instsimplify" gets
the sibling fold when the predicate is "ne", but we miss this:

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