[llvm] IR: introduce CmpInst::isEquivalence (PR #111979)

[Nikita Popov via llvm-commits]

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@@ -3471,6 +3472,44 @@ bool CmpInst::isEquality(Predicate P) {
   llvm_unreachable("Unsupported predicate kind");
 }
 
+// Returns true if either operand of CmpInst is a provably non-zero
+// floating-point constant.
+static bool hasNonZeroFPOperands(const CmpInst *Cmp) {
+  auto *LHS = dyn_cast<Constant>(Cmp->getOperand(0));
+  auto *RHS = dyn_cast<Constant>(Cmp->getOperand(1));
+  if (auto *Const = LHS ? LHS : RHS) {
+    using namespace llvm::PatternMatch;
+    return match(Const, m_NonZeroNotDenormalFP());
+  }
+  return false;
+}
+
+// Floating-point equality is not an equivalence when comparing +0.0 with
+// -0.0, when comparing NaN with another value, or when flushing
+// denormals-to-zero.
+bool CmpInst::isEquivalence(bool Invert) const {
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nikic wrote:

For Invert=true you should invert the predicate, instead of duplicating the checks.

https://github.com/llvm/llvm-project/pull/111979