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

[Justin Bogner via llvm-commits]

================
@@ -0,0 +1,224 @@
+//===- 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/Metadata.h"
+#include "llvm/IR/Module.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/ErrorHandling.h"
+#include <cstdint>
+#include <optional>
+#include <utility>
+
+using namespace llvm;
+using namespace llvm::dxil;
+
+static bool reportError(LLVMContext *Ctx, Twine Message,
+                        DiagnosticSeverity Severity = DS_Error) {
+  Ctx->diagnose(DiagnosticInfoGeneric(Message, Severity));
+  return true;
+}
+
+static bool parseRootFlags(LLVMContext *Ctx, ModuleRootSignature &MRS,
+                           MDNode *RootFlagNode) {
+
+  if (RootFlagNode->getNumOperands() != 2)
+    return reportError(Ctx, "Invalid format for RootFlag Element");
+
+  auto *Flag = mdconst::extract<ConstantInt>(RootFlagNode->getOperand(1));
+  MRS.Flags = Flag->getZExtValue();
+
+  return false;
+}
+
+static bool parseRootSignatureElement(LLVMContext *Ctx,
+                                      ModuleRootSignature &MRS,
+                                      MDNode *Element) {
+  MDString *ElementText = cast<MDString>(Element->getOperand(0));
+  if (ElementText == nullptr)
+    return reportError(Ctx, "Invalid format for Root Element");
+
+  RootSignatureElementKind ElementKind =
+      StringSwitch<RootSignatureElementKind>(ElementText->getString())
+          .Case("RootFlags", RootSignatureElementKind::RootFlags)
+          .Default(RootSignatureElementKind::None);
+
+  switch (ElementKind) {
+
+  case RootSignatureElementKind::RootFlags:
+    return parseRootFlags(Ctx, MRS, Element);
+  case RootSignatureElementKind::None:
+    return reportError(Ctx, "Invalid Root Signature Element: " +
+                                ElementText->getString());
+  }
+
+  llvm_unreachable("Root signature element kind not expected.");
+}
+
+static bool parse(LLVMContext *Ctx, ModuleRootSignature &MRS, MDNode *Node) {
+  bool HasError = false;
+
+  // Loop through the Root Elements of the root signature.
+  for (const auto &Operand : Node->operands()) {
+    MDNode *Element = dyn_cast<MDNode>(Operand);
+    if (Element == nullptr)
+      return reportError(Ctx, "Missing Root Element Metadata Node.");
+
+    HasError = HasError || parseRootSignatureElement(Ctx, MRS, Element);
+  }
+
+  return HasError;
+}
+
+static bool validate(LLVMContext *Ctx, const ModuleRootSignature &MRS) {
+  if (!dxbc::RootSignatureValidations::isValidRootFlag(MRS.Flags)) {
+    return reportError(Ctx, "Invalid Root Signature flag value");
+  }
+  return false;
+}
+
+static SmallDenseMap<const Function *, ModuleRootSignature>
+analyzeModule(Module &M) {
+
+  /** 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 its operands and process the function,
+    signature pair.
+ */
+
+  LLVMContext *Ctx = &M.getContext();
+
+  SmallDenseMap<const Function *, ModuleRootSignature> MRSMap;
+
+  NamedMDNode *RootSignatureNode = M.getNamedMetadata("dx.rootsignatures");
+  if (RootSignatureNode == nullptr)
+    return MRSMap;
+
+  for (const auto &RSDefNode : RootSignatureNode->operands()) {
+    if (RSDefNode->getNumOperands() != 2) {
+      reportError(Ctx, "Invalid format for Root Signature Definition. Pairs "
+                       "of function, root signature expected.");
+      continue;
+    }
+
+    // Function was pruned during compilation.
+    const MDOperand &FunctionPointerMdNode = RSDefNode->getOperand(0);
+    if (FunctionPointerMdNode == nullptr) {
+      continue;
+    }
----------------
bogner wrote:

This should probably be a `reportError`, and we should test it. We should not get here normally, and if we do, we were given invalid IR.

(there's an argument that some of these could be asserts, depending on whether we consider invalid IR to be user input or a frontend bug, but for consistency with the other cases here reportError seems the most appropriate)

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