[llvm-branch-commits] [llvm] [HLSL] Adding support for Root Constants in LLVM Metadata (PR #135085)

[Finn Plummer via llvm-branch-commits]

================
@@ -52,6 +59,45 @@ static bool parseRootFlags(LLVMContext *Ctx, mcdxbc::RootSignatureDesc &RSD,
   return false;
 }
 
+static bool extractMdValue(uint32_t &Value, MDNode *Node, unsigned int OpId) {
+
+  auto *CI = mdconst::extract<ConstantInt>(Node->getOperand(OpId));
+  if (CI == nullptr)
+    return true;
+
+  Value = CI->getZExtValue();
+  return false;
+}
+
+static bool parseRootConstants(LLVMContext *Ctx, mcdxbc::RootSignatureDesc &RSD,
+                               MDNode *RootFlagNode) {
+
+  if (RootFlagNode->getNumOperands() != 5)
+    return reportError(Ctx, "Invalid format for RootConstants Element");
+
+  mcdxbc::RootParameter NewParameter;
+  NewParameter.Header.ParameterType = dxbc::RootParameterType::Constants32Bit;
+
+  uint32_t SV;
+  if (extractMdValue(SV, RootFlagNode, 1))
+    return reportError(Ctx, "Invalid value for ShaderVisibility");
+
+  NewParameter.Header.ShaderVisibility = (dxbc::ShaderVisibility)SV;
+
+  if (extractMdValue(NewParameter.Constants.ShaderRegister, RootFlagNode, 2))
+    return reportError(Ctx, "Invalid value for ShaderRegister");
+
+  if (extractMdValue(NewParameter.Constants.RegisterSpace, RootFlagNode, 3))
+    return reportError(Ctx, "Invalid value for RegisterSpace");
+
+  if (extractMdValue(NewParameter.Constants.Num32BitValues, RootFlagNode, 4))
+    return reportError(Ctx, "Invalid value for Num32BitValues");
----------------
inbelic wrote:

Only the "Invalid value for ShaderVisibility" has a test demonstrating its functionality. Maybe it is too verbose to include a test case for each diag type, or, they are all reporting the same error (expected an i32) and we could move that logic into `extractMdValue`?

https://github.com/llvm/llvm-project/pull/135085