[llvm] [DXIL] Add support for root signature flag element in DXContainer (PR #123147)

[Damyan Pepper via llvm-commits]

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@@ -0,0 +1,196 @@
+//===- DXILRootSignature.cpp - DXIL Root Signature helper objects ----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file This file contains helper objects and APIs for working with DXIL
+///       Root Signatures.
+///
+//===----------------------------------------------------------------------===//
+#include "DXILRootSignature.h"
+#include "DirectX.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Analysis/DXILMetadataAnalysis.h"
+#include "llvm/BinaryFormat/DXContainer.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Error.h"
+#include <optional>
+
+using namespace llvm;
+using namespace llvm::dxil;
+
+bool ModuleRootSignature::reportError(Twine Message,
+                                      DiagnosticSeverity Severity) {
+  Ctx->diagnose(DiagnosticInfoGeneric(Message, Severity));
+  return true;
+}
+
+bool ModuleRootSignature::parseRootFlags(MDNode *RootFlagNode) {
+
+  if (RootFlagNode->getNumOperands() != 2)
+    return reportError("Invalid format for RootFlag Element");
+
+  auto *Flag = mdconst::extract<ConstantInt>(RootFlagNode->getOperand(1));
+  this->Flags = Flag->getZExtValue();
+
+  return false;
+}
+
+bool ModuleRootSignature::parseRootSignatureElement(MDNode *Element) {
+  MDString *ElementText = cast<MDString>(Element->getOperand(0));
+  if (ElementText == nullptr)
+    return reportError("Invalid format for Root Element");
+
+  RootSignatureElementKind ElementKind =
+      StringSwitch<RootSignatureElementKind>(ElementText->getString())
+          .Case("RootFlags", RootSignatureElementKind::RootFlags)
+          .Case("RootConstants", RootSignatureElementKind::RootConstants)
+          .Case("RootCBV", RootSignatureElementKind::RootDescriptor)
+          .Case("RootSRV", RootSignatureElementKind::RootDescriptor)
+          .Case("RootUAV", RootSignatureElementKind::RootDescriptor)
+          .Case("Sampler", RootSignatureElementKind::RootDescriptor)
+          .Case("DescriptorTable", RootSignatureElementKind::DescriptorTable)
+          .Case("StaticSampler", RootSignatureElementKind::StaticSampler)
+          .Default(RootSignatureElementKind::None);
+
+  switch (ElementKind) {
+
+  case RootSignatureElementKind::RootFlags: {
+    return parseRootFlags(Element);
+    break;
+  }
+
+  case RootSignatureElementKind::RootConstants:
+  case RootSignatureElementKind::RootDescriptor:
+  case RootSignatureElementKind::DescriptorTable:
+  case RootSignatureElementKind::StaticSampler:
+  case RootSignatureElementKind::None:
+    return reportError("Invalid Root Element: " + ElementText->getString());
+    break;
+  }
+
+  return true;
+}
+
+bool ModuleRootSignature::parse(NamedMDNode *Root, const Function *EF) {
+  bool HasError = false;
+
+  /** Root Signature are specified as following in the metadata:
+
+      !dx.rootsignatures = !{!2} ; list of function/root signature pairs
+      !2 = !{ ptr @main, !3 } ; function, root signature
+      !3 = !{ !4, !5, !6, !7 } ; list of root signature elements
+
+      So for each MDNode inside dx.rootsignatures NamedMDNode
+      (the Root parameter of this function), the parsing process needs
+      to loop through each of it's operand and process the pairs function
+      signature pair.
+   */
+
+  for (const MDNode *Node : Root->operands()) {
+    if (Node->getNumOperands() != 2)
+      return reportError("Invalid format for Root Signature Definition. Pairs "
+                         "of function, root signature expected.");
----------------
damyanp wrote:

> is not possible to proceed if the root signature metadata element is incorrectly defined. That is why it fails immediately.

I'm not sure this is true.  Can't we just move onto the next element if one is malformed?

https://github.com/llvm/llvm-project/pull/123147