[llvm] [IR] Composable and Extensible Memory Cache Control Hints (PR #181612)

[Antonio Frighetto via llvm-commits]

================
@@ -5631,6 +5632,66 @@ void Verifier::visitInlineHistoryMetadata(Instruction &I, MDNode *MD) {
   }
 }
 
+void Verifier::visitMemCacheHintMetadata(Instruction &I, MDNode *MD) {
+  Check(I.mayReadOrWriteMemory(),
+        "!mem.cache_hint is only valid on memory operations", &I);
+
+  Check(MD->getNumOperands() % 2 == 0,
+        "!mem.cache_hint must have even number of operands "
+        "(operand_no, hint_node pairs)",
+        MD);
+
+  const auto *CB = dyn_cast<CallBase>(&I);
+  if (CB)
+    Check(CB->getIntrinsicID() != Intrinsic::not_intrinsic,
+          "!mem.cache_hint is not supported on non-intrinsic calls", &I);
+
+  unsigned NumOperands = CB ? CB->arg_size() : I.getNumOperands();
+
+  SmallDenseSet<unsigned, 4> SeenOperandNos;
+
+  // Top-level metadata alternates: i32 operand_no, MDNode hint_node.
+  for (unsigned i = 0; i + 1 < MD->getNumOperands(); i += 2) {
+    auto *OpNoCI = mdconst::dyn_extract<ConstantInt>(MD->getOperand(i));
+    Check(OpNoCI,
+          "!mem.cache_hint operand_no must be an integer constant in pair", MD);
+
+    Check(OpNoCI->getValue().isNonNegative(),
+          "!mem.cache_hint operand_no must be non-negative", MD);
+
+    uint64_t OperandNo = OpNoCI->getZExtValue();
+    Check(OperandNo < NumOperands, "!mem.cache_hint operand_no is out of range",
+          &I);
+
+    Value *Operand =
+        CB ? CB->getArgOperand(OperandNo) : I.getOperand(OperandNo);
+    Check(Operand->getType()->isPtrOrPtrVectorTy(),
+          "!mem.cache_hint operand_no must refer to a pointer operand", &I);
+
+    Check(SeenOperandNos.insert(OperandNo).second,
+          "!mem.cache_hint contains duplicate operand_no", MD);
+
+    const auto *Node = dyn_cast<MDNode>(MD->getOperand(i + 1));
+    Check(Node, "!mem.cache_hint hint node must be a metadata node", MD);
+
+    Check(Node->getNumOperands() % 2 == 0,
+          "!mem.cache_hint hint node must have even number of operands "
+          "(key-value pairs)",
+          Node);
+
+    SmallDenseSet<StringRef, 8> SeenKeys;
----------------
antoniofrighetto wrote:

I would use a StringSet here, but not strong.

https://github.com/llvm/llvm-project/pull/181612