[llvm] [InstCombine] Fix the correctness of missing check reassoc attribute (PR #71277)

[Matt Arsenault via llvm-commits]

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@@ -321,6 +321,27 @@ void Instruction::setNonNeg(bool b) {
                          (b * PossiblyNonNegInst::NonNeg);
 }
 
+bool Instruction::hasAllowReassocOfAllOperand() const {
+  return all_of(operands(), [](Value *V) {
+    if (!isa<FPMathOperator>(V))
+      return true;
+
+    auto *FPOp = cast<FPMathOperator>(V);
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arsenm wrote:

dyn_cast instead of isa+cast 

https://github.com/llvm/llvm-project/pull/71277