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

[via llvm-commits]

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@@ -946,6 +946,56 @@ class PossiblyNonNegInst : public CastInst {
   }
 };
 
+/// Cast Instruction that can have a nowrap flags (only trunc)
+class PossiblyNoWrapInst : public CastInst {
+public:
+  enum { AnyWrap = 0, NoUnsignedWrap = (1 << 0), NoSignedWrap = (1 << 1) };
+
+  static bool classof(const Instruction *I) {
+    return I->getOpcode() == Instruction::Trunc;
+  }
+
+  static bool classof(const Value *V) {
+    return isa<Instruction>(V) && classof(cast<Instruction>(V));
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elhewaty wrote:

In the internal `classof` there's a check `I->getOpcode() == Instrucntion::Trunc`, 
won't `dyn_cast` cause a null pointer dereference?

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