[llvm] [HLSL] Add descriptor table metadata parsing (PR #142492)

[Finn Plummer via llvm-commits]

================
@@ -174,6 +174,94 @@ static bool parseRootDescriptors(LLVMContext *Ctx,
   return false;
 }
 
+static bool parseDescriptorRange(LLVMContext *Ctx,
+                                 mcdxbc::RootSignatureDesc &RSD,
+                                 mcdxbc::DescriptorTable &Table,
+                                 MDNode *RangeDescriptorNode) {
+
+  if (RangeDescriptorNode->getNumOperands() != 6)
+    return reportError(Ctx, "Invalid format for Descriptor Range");
+
+  dxbc::RTS0::v2::DescriptorRange Range;
+
+  std::optional<StringRef> ElementText =
+      extractMdStringValue(RangeDescriptorNode, 0);
+
+  if (!ElementText.has_value())
+    return reportError(Ctx, "Descriptor Range, first element is not a string.");
+
+  Range.RangeType =
+      StringSwitch<uint32_t>(*ElementText)
+          .Case("CBV", llvm::to_underlying(dxbc::DescriptorRangeType::CBV))
+          .Case("SRV", llvm::to_underlying(dxbc::DescriptorRangeType::SRV))
+          .Case("UAV", llvm::to_underlying(dxbc::DescriptorRangeType::UAV))
+          .Case("Sampler",
+                llvm::to_underlying(dxbc::DescriptorRangeType::Sampler))
+          .Default(-1u);
+
+  if (Range.RangeType == -1u)
+    return reportError(Ctx, "Invalid Descriptor Range type: " + *ElementText);
+
+  if (std::optional<uint32_t> Val = extractMdIntValue(RangeDescriptorNode, 1))
+    Range.NumDescriptors = *Val;
+  else
+    return reportError(Ctx, "Invalid value for Number of Descriptor in Range");
+
+  if (std::optional<uint32_t> Val = extractMdIntValue(RangeDescriptorNode, 2))
+    Range.BaseShaderRegister = *Val;
+  else
+    return reportError(Ctx, "Invalid value for BaseShaderRegister");
+
+  if (std::optional<uint32_t> Val = extractMdIntValue(RangeDescriptorNode, 3))
+    Range.RegisterSpace = *Val;
+  else
+    return reportError(Ctx, "Invalid value for RegisterSpace");
+
+  if (std::optional<uint32_t> Val = extractMdIntValue(RangeDescriptorNode, 4))
+    Range.OffsetInDescriptorsFromTableStart = *Val;
+  else
+    return reportError(Ctx,
+                       "Invalid value for OffsetInDescriptorsFromTableStart");
+
+  if (std::optional<uint32_t> Val = extractMdIntValue(RangeDescriptorNode, 5))
+    Range.Flags = *Val;
+  else
+    return reportError(Ctx, "Invalid value for Descriptor Range Flags");
+
+  Table.Ranges.push_back(Range);
+  return false;
+}
+
+static bool parseDescriptorTable(LLVMContext *Ctx,
+                                 mcdxbc::RootSignatureDesc &RSD,
+                                 MDNode *DescriptorTableNode) {
+  const unsigned int NumOperands = DescriptorTableNode->getNumOperands();
+  if (NumOperands < 2)
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inbelic wrote:

I think you could have a descriptor table with no elements and just the visibility right? So couldn't NumOperands be 1

https://github.com/llvm/llvm-project/pull/142492