[llvm] [InstCombine] Canonicalize fcmp with inf (PR #80986)

[Yingwei Zheng via llvm-commits]

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@@ -7751,6 +7751,48 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
   if (match(Op1, m_AnyZeroFP()) && !match(Op1, m_PosZeroFP()))
     return replaceOperand(I, 1, ConstantFP::getZero(OpType));
 
+  // Canonicalize:
+  // fcmp olt X, +inf -> fcmp one X, +inf
+  // fcmp ole X, +inf -> fcmp ord X, 0
+  // fcmp ogt X, +inf -> false
+  // fcmp oge X, +inf -> fcmp oeq X, +inf
+  // fcmp ult X, +inf -> fcmp une X, +inf
+  // fcmp ule X, +inf -> true
+  // fcmp ugt X, +inf -> fcmp uno X, 0
+  // fcmp uge X, +inf -> fcmp ueq X, +inf
+  // fcmp olt X, -inf -> false
+  // fcmp ole X, -inf -> fcmp oeq X, -inf
+  // fcmp ogt X, -inf -> fcmp one X, -inf
+  // fcmp oge X, -inf -> fcmp ord X, 0
+  // fcmp ult X, -inf -> fcmp uno X, 0
+  // fcmp ule X, -inf -> fcmp ueq X, -inf
+  // fcmp ugt X, -inf -> fcmp une X, -inf
+  // fcmp uge X, -inf -> true
+  const APFloat *C;
+  if (match(Op1, m_APFloat(C)) && C->isInfinity()) {
+    switch (C->isNegative() ? FCmpInst::getSwappedPredicate(Pred) : Pred) {
+    default:
+      break;
+    case FCmpInst::FCMP_OGT:
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dtcxzyw wrote:

Done.

https://github.com/llvm/llvm-project/pull/80986