CmpInst: de-duplicate code; address review

Author: artagnon

llvm/include/llvm/IR/InstrTypes.h

@@ -913,9 +913,8 @@ class CmpInst : public Instruction {
   bool isEquality() const { return isEquality(getPredicate()); }
 
   /// Determine if one operand of this compare can always be replaced by the
-  /// other operand, ignoring provenance considerations. If \p Invert is false,
-  /// check for equivalence with an equals predicate; otherwise, check for
-  /// equivalence with a not-equals predicate.
+  /// other operand, ignoring provenance considerations. If \p Invert, check for
+  /// equivalence with the inverse predicate.
   bool isEquivalence(bool Invert = false) const;
 
   /// Return true if the predicate is relational (not EQ or NE).

llvm/lib/IR/Instructions.cpp

@@ -3488,23 +3488,15 @@ static bool hasNonZeroFPOperands(const CmpInst *Cmp) {
 // -0.0, when comparing NaN with another value, or when flushing
 // denormals-to-zero.
 bool CmpInst::isEquivalence(bool Invert) const {
-  switch (getPredicate()) {
+  switch (Invert ? getInversePredicate() : getPredicate()) {
   case CmpInst::Predicate::ICMP_EQ:
-    return !Invert;
-  case CmpInst::Predicate::ICMP_NE:
-    return Invert;
+    return true;
   case CmpInst::Predicate::FCMP_UEQ:
     if (!hasNoNaNs())
       return false;
     [[fallthrough]];
   case CmpInst::Predicate::FCMP_OEQ:
-    return !Invert && hasNonZeroFPOperands(this);
-  case CmpInst::Predicate::FCMP_ONE:
-    if (!hasNoNaNs())
-      return false;
-    [[fallthrough]];
-  case CmpInst::Predicate::FCMP_UNE:
-    return Invert && hasNonZeroFPOperands(this);
+    return hasNonZeroFPOperands(this);
   default:
     return false;
   }