================
@@ -314,16 +327,106 @@ static void translateBranchMetadata(Module &M,
Instruction *BBTerminatorInst) {
BBTerminatorInst->setMetadata("hlsl.controlflow.hint", nullptr);
}
-static std::array<unsigned, 6> getCompatibleInstructionMDs(llvm::Module &M) {
+// Determines if the metadata node will be compatible with DXIL's loop metadata
+// representation.
+//
+// Reports an error for compatible metadata that is ill-formed.
+static bool isLoopMDCompatible(Module &M, Metadata *MD) {
+ // DXIL only accepts the following loop hints:
+ std::array<StringLiteral, 3> ValidHintNames = {"llvm.loop.unroll.count",
+ "llvm.loop.unroll.disable",
+ "llvm.loop.unroll.full"};
+
+ MDNode *HintMD = dyn_cast<MDNode>(MD);
+ if (!HintMD || HintMD->getNumOperands() == 0)
+ return false;
+
+ auto *HintStr = dyn_cast<MDString>(HintMD->getOperand(0));
+ if (!HintStr)
+ return false;
+
+ if (!llvm::is_contained(ValidHintNames, HintStr->getString()))
+ return false;
+
+ auto ValidCountNode = [](MDNode *CountMD) -> bool {
+ if (CountMD->getNumOperands() == 2)
+ if (auto *Count = dyn_cast<ConstantAsMetadata>(CountMD->getOperand(1)))
+ if (isa<ConstantInt>(Count->getValue()))
+ return true;
+ return false;
+ };
+
+ if (HintStr->getString() == "llvm.loop.unroll.count") {
+ if (!ValidCountNode(HintMD))
+ return reportLoopError(M, "Second operand of \"llvm.loop.unroll.count\" "
+ "must be a constant integer");
+ } else if (HintMD->getNumOperands() != 1)
+ return reportLoopError(
+ M, "\"llvm.loop.unroll.disable\" and \"llvm.loop.unroll.disable\" "
+ "must be provided as a single operand");
+
+ return true;
+}
+
+static void translateLoopMetadata(Module &M, Instruction *I, MDNode *BaseMD) {
+ // A distinct node has the self-referential form: !0 = !{ !0, ... }
+ auto IsDistinctNode = [](MDNode *Node) -> bool {
+ return Node && Node->getNumOperands() != 0 && Node == Node->getOperand(0);
+ };
+
+ // Strip empty metadata or a non-distinct node
+ if (BaseMD->getNumOperands() == 0 || !IsDistinctNode(BaseMD))
+ return I->setMetadata("llvm.loop", nullptr);
+
+ // It is valid to have a chain of self-refential loop metadata nodes, as
+ // below. We will collapse these into just one when we reconstruct the
+ // metadata.
+ //
+ // Eg:
+ // !0 = !{!0, !1}
+ // !1 = !{!1, !2}
+ // !2 = !{!"llvm.loop.unroll.disable"}
+ //
+ // So, traverse down a potential self-referential chain
+ while (1 < BaseMD->getNumOperands() &&
+ IsDistinctNode(dyn_cast<MDNode>(BaseMD->getOperand(1))))
+ BaseMD = dyn_cast<MDNode>(BaseMD->getOperand(1));
+
+ // To reconstruct a distinct node we create a temporary node that we will
+ // then update to create a self-reference.
+ llvm::TempMDTuple TempNode = llvm::MDNode::getTemporary(M.getContext(), {});
+ SmallVector<Metadata *> CompatibleOperands = {TempNode.get()};
+
+ // Iterate and reconstruct the metadata nodes that contains any hints,
+ // stripping any unrecognized metadata.
+ ArrayRef<MDOperand> Operands = BaseMD->operands();
+ for (auto &Op : Operands.drop_front())
+ if (isLoopMDCompatible(M, Op.get()))
+ CompatibleOperands.push_back(Op.get());
----------------
hekota wrote:
Please add a test case with unrecognized loop metadata hint that gets stripped.
https://github.com/llvm/llvm-project/pull/164292
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