[llvm] [IR] Add nowrap flags for trunc instruction (PR #85592)

[via llvm-commits]

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@@ -386,11 +394,17 @@ void Instruction::setNonNeg(bool b) {
 }
 
 bool Instruction::hasNoUnsignedWrap() const {
-  return cast<OverflowingBinaryOperator>(this)->hasNoUnsignedWrap();
+  if (auto Inst = cast<OverflowingBinaryOperator>(this))
+    return Inst->hasNoUnsignedWrap();
+
+  return cast<PossiblyNoWrapInst>(this)->hasNoUnsignedWrap();
 }
 
 bool Instruction::hasNoSignedWrap() const {
-  return cast<OverflowingBinaryOperator>(this)->hasNoSignedWrap();
+  if (auto Inst = cast<OverflowingBinaryOperator>(this))
+    return Inst->hasNoSignedWrap();
+
+  return cast<PossiblyNoWrapInst>(this)->hasNoSignedWrap();
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elhewaty wrote:

We can change the name of `OverflowingBinaryOperator` class to something 
that works for `trunc` too, but I am afraid that they will be handled differently later in the pipeline.

https://github.com/llvm/llvm-project/pull/85592