[clang] [HLSL] Global resource arrays element access (PR #152454)

[Chris B via cfe-commits]

================
@@ -84,6 +85,111 @@ void addRootSignature(llvm::dxbc::RootSignatureVersion RootSigVer,
   RootSignatureValMD->addOperand(MDVals);
 }
 
+// Find array variable declaration from nested array subscript AST nodes
+static const ValueDecl *getArrayDecl(const ArraySubscriptExpr *ASE) {
+  const Expr *E = nullptr;
+  while (ASE != nullptr) {
+    E = ASE->getBase()->IgnoreImpCasts();
+    if (!E)
+      return nullptr;
+    ASE = dyn_cast<ArraySubscriptExpr>(E);
+  }
+  if (const DeclRefExpr *DRE = dyn_cast_or_null<DeclRefExpr>(E))
+    return DRE->getDecl();
+  return nullptr;
+}
+
+// Get the total size of the array, or -1 if the array is unbounded.
+static int getTotalArraySize(ASTContext &AST, const clang::Type *Ty) {
+  Ty = Ty->getUnqualifiedDesugaredType();
+  assert(Ty->isArrayType() && "expected array type");
+  if (Ty->isIncompleteArrayType())
+    return -1;
+  return AST.getConstantArrayElementCount(cast<ConstantArrayType>(Ty));
+}
+
+// Find constructor decl for a specific resource record type and binding
+// (implicit vs. explicit). The constructor has 5 parameters.
+// For explicit binding the signature is:
+//   void(unsigned, unsigned, int, unsigned, const char *).
+// For implicit binding the signature is:
+//   void(unsigned, int, unsigned, unsigned, const char *).
+static CXXConstructorDecl *findResourceConstructorDecl(ASTContext &AST,
+                                                       QualType ResTy,
+                                                       bool ExplicitBinding) {
+  std::array<QualType, 5> ExpParmTypes = {
+      AST.UnsignedIntTy, AST.UnsignedIntTy, AST.UnsignedIntTy,
+      AST.UnsignedIntTy, AST.getPointerType(AST.CharTy.withConst())};
+  ExpParmTypes[ExplicitBinding ? 2 : 1] = AST.IntTy;
+
+  CXXRecordDecl *ResDecl = ResTy->getAsCXXRecordDecl();
+  for (auto *Ctor : ResDecl->ctors()) {
+    if (Ctor->getNumParams() != ExpParmTypes.size())
+      continue;
+    auto *ParmIt = Ctor->param_begin();
+    auto ExpTyIt = ExpParmTypes.begin();
+    for (; ParmIt != Ctor->param_end() && ExpTyIt != ExpParmTypes.end();
+         ++ParmIt, ++ExpTyIt) {
+      if ((*ParmIt)->getType() != *ExpTyIt)
+        break;
+    }
+    if (ParmIt == Ctor->param_end())
+      return Ctor;
+  }
+  llvm_unreachable("did not find constructor for resource class");
+}
+
+static Value *buildNameForResource(llvm::StringRef BaseName,
+                                   CodeGenModule &CGM) {
+  llvm::SmallString<64> GlobalName = {BaseName, ".str"};
+  return CGM.GetAddrOfConstantCString(BaseName.str(), GlobalName.c_str())
+      .getPointer();
+}
+
+static void createResourceCtorArgs(CodeGenModule &CGM, CXXConstructorDecl *CD,
+                                   llvm::Value *ThisPtr, llvm::Value *Range,
+                                   llvm::Value *Index, StringRef Name,
+                                   HLSLResourceBindingAttr *RBA,
+                                   HLSLVkBindingAttr *VkBinding,
+                                   CallArgList &Args) {
+  assert((VkBinding || RBA) && "at least one a binding attribute expected");
+
+  std::optional<uint32_t> RegisterSlot;
+  uint32_t SpaceNo = 0;
+  if (VkBinding) {
+    RegisterSlot = VkBinding->getBinding();
+    SpaceNo = VkBinding->getSet();
+  } else {
+    if (RBA->hasRegisterSlot())
+      RegisterSlot = RBA->getSlotNumber();
+    SpaceNo = RBA->getSpaceNumber();
+  }
+
+  ASTContext &AST = CD->getASTContext();
+  Value *NameStr = buildNameForResource(Name, CGM);
+  Value *Space = llvm::ConstantInt::get(CGM.IntTy, SpaceNo);
+
+  Args.add(RValue::get(ThisPtr), CD->getThisType());
+  if (RegisterSlot.has_value()) {
+    // explicit binding
+    auto *RegSlot = llvm::ConstantInt::get(CGM.IntTy, RegisterSlot.value());
+    Args.add(RValue::get(RegSlot), AST.UnsignedIntTy);
+    Args.add(RValue::get(Space), AST.UnsignedIntTy);
+    Args.add(RValue::get(Range), AST.IntTy);
+    Args.add(RValue::get(Index), AST.UnsignedIntTy);
+
+  } else {
+    // implicit binding
+    auto *OrderID =
+        llvm::ConstantInt::get(CGM.IntTy, RBA->getImplicitBindingOrderID());
----------------
llvm-beanz wrote:

Since the logic here is a bit unclear, maybe it warrants an assert to ensure that the surrounding code never changes the preconditions?

https://github.com/llvm/llvm-project/pull/152454