[llvm] [IR] Initial introduction of memset_pattern (PR #97583)

[Alex Bradbury via llvm-commits]

================
@@ -1263,6 +1263,41 @@ class MemSetInlineInst : public MemSetInst {
   }
 };
 
+/// This is the base class for llm.experimental.memset.pattern
+class MemSetPatternIntrinsic : public MemIntrinsicBase<MemIntrinsic> {
+private:
+  enum { ARG_VOLATILE = 3 };
+
+public:
+  ConstantInt *getVolatileCst() const {
+    return cast<ConstantInt>(const_cast<Value *>(getArgOperand(ARG_VOLATILE)));
+  }
+
+  bool isVolatile() const { return !getVolatileCst()->isZero(); }
+
+  void setVolatile(Constant *V) { setArgOperand(ARG_VOLATILE, V); }
+
+  // Methods for support of type inquiry through isa, cast, and dyn_cast:
+  static bool classof(const IntrinsicInst *I) {
+    return I->getIntrinsicID() == Intrinsic::experimental_memset_pattern;
+  }
+  static bool classof(const Value *V) {
+    return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
+  }
+};
+
+/// This class wraps the llvm.experimental.memset.pattern intrinsic.
+class MemSetPatternInst : public MemSetBase<MemSetPatternIntrinsic> {
+public:
+  // Methods for support type inquiry through isa, cast, and dyn_cast:
+  static bool classof(const IntrinsicInst *I) {
+    return I->getIntrinsicID() == Intrinsic::experimental_memset_pattern;
+  }
+  static bool classof(const Value *V) {
+    return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
+  }
+};
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asb wrote:

I'm mirroring the pattern followed by other mem intrinsics, and although it's not super pretty, having both classes like this (as for the standard MemSet intrinsics) seems the way that reduces copy and paste of accessor code.

https://github.com/llvm/llvm-project/pull/97583