[HLSL] cbuffer: create host layout structs (#122820)

Creates layout struct for `cbuffer` in Sema which will contains only
declarations contributing to the constant buffer layout. Anything else
will be filtered out, such as static variables decls, struct and
function definitions, resources, or empty struct and zero-sized arrays.

If the constant buffer includes a struct that contains any of the above
undesirable declarations, a new version of this struct should be created
with these declarations filtered out as well.

The definition of buffer layout struct will be added to the
HLSLBufferDecl AST node as the last node. Any layout structs for
embedded structures will be added there as well.

Fixes #122553

Author: hekota

clang/lib/Sema/SemaHLSL.cpp

@@ -15,12 +15,14 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclarationName.h"
 #include "clang/AST/DynamicRecursiveASTVisitor.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/Type.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/Builtins.h"
 #include "clang/Basic/DiagnosticSema.h"
+#include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/TargetInfo.h"
@@ -32,16 +34,21 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/DXILABI.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/TargetParser/Triple.h"
+#include <cstddef>
 #include <iterator>
 #include <utility>
 
 using namespace clang;
 using RegisterType = HLSLResourceBindingAttr::RegisterType;
 
+static CXXRecordDecl *createHostLayoutStruct(Sema &S,
+                                             CXXRecordDecl *StructDecl);
+
 static RegisterType getRegisterType(ResourceClass RC) {
   switch (RC) {
   case ResourceClass::SRV:
@@ -253,12 +260,244 @@ static void validatePackoffset(Sema &S, HLSLBufferDecl *BufDecl) {
   }
 }
 
+// Returns true if the array has a zero size = if any of the dimensions is 0
+static bool isZeroSizedArray(const ConstantArrayType *CAT) {
+  while (CAT && !CAT->isZeroSize())
+    CAT = dyn_cast<ConstantArrayType>(
+        CAT->getElementType()->getUnqualifiedDesugaredType());
+  return CAT != nullptr;
+}
+
+// Returns true if the record type is an HLSL resource class
+static bool isResourceRecordType(const Type *Ty) {
+  return HLSLAttributedResourceType::findHandleTypeOnResource(Ty) != nullptr;
+}
+
+// Returns true if the type is a leaf element type that is not valid to be
+// included in HLSL Buffer, such as a resource class, empty struct, zero-sized
+// array, or a builtin intangible type. Returns false it is a valid leaf element
+// type or if it is a record type that needs to be inspected further.
+static bool isInvalidConstantBufferLeafElementType(const Type *Ty) {
+  if (Ty->isRecordType()) {
+    if (isResourceRecordType(Ty) || Ty->getAsCXXRecordDecl()->isEmpty())
+      return true;
+    return false;
+  }
+  if (Ty->isConstantArrayType() &&
+      isZeroSizedArray(cast<ConstantArrayType>(Ty)))
+    return true;
+  if (Ty->isHLSLBuiltinIntangibleType())
+    return true;
+  return false;
+}
+
+// Returns true if the struct contains at least one element that prevents it
+// from being included inside HLSL Buffer as is, such as an intangible type,
+// empty struct, or zero-sized array. If it does, a new implicit layout struct
+// needs to be created for HLSL Buffer use that will exclude these unwanted
+// declarations (see createHostLayoutStruct function).
+static bool requiresImplicitBufferLayoutStructure(const CXXRecordDecl *RD) {
+  if (RD->getTypeForDecl()->isHLSLIntangibleType() || RD->isEmpty())
+    return true;
+  // check fields
+  for (const FieldDecl *Field : RD->fields()) {
+    QualType Ty = Field->getType();
+    if (isInvalidConstantBufferLeafElementType(Ty.getTypePtr()))
+      return true;
+    if (Ty->isRecordType() &&
+        requiresImplicitBufferLayoutStructure(Ty->getAsCXXRecordDecl()))
+      return true;
+  }
+  // check bases
+  for (const CXXBaseSpecifier &Base : RD->bases())
+    if (requiresImplicitBufferLayoutStructure(
+            Base.getType()->getAsCXXRecordDecl()))
+      return true;
+  return false;
+}
+
+static CXXRecordDecl *findRecordDeclInContext(IdentifierInfo *II,
+                                              DeclContext *DC) {
+  CXXRecordDecl *RD = nullptr;
+  for (NamedDecl *Decl :
+       DC->getNonTransparentContext()->lookup(DeclarationName(II))) {
+    if (CXXRecordDecl *FoundRD = dyn_cast<CXXRecordDecl>(Decl)) {
+      assert(RD == nullptr &&
+             "there should be at most 1 record by a given name in a scope");
+      RD = FoundRD;
+    }
+  }
+  return RD;
+}
+
+// Creates a name for buffer layout struct using the provide name base.
+// If the name must be unique (not previously defined), a suffix is added
+// until a unique name is found.
+static IdentifierInfo *getHostLayoutStructName(Sema &S, NamedDecl *BaseDecl,
+                                               bool MustBeUnique) {
+  ASTContext &AST = S.getASTContext();
+
+  IdentifierInfo *NameBaseII = BaseDecl->getIdentifier();
+  llvm::SmallString<64> Name("__layout_");
+  if (NameBaseII) {
+    Name.append(NameBaseII->getName());
+  } else {
+    // anonymous struct
+    Name.append("anon");
+    MustBeUnique = true;
+  }
+
+  size_t NameLength = Name.size();
+  IdentifierInfo *II = &AST.Idents.get(Name, tok::TokenKind::identifier);
+  if (!MustBeUnique)
+    return II;
+
+  unsigned suffix = 0;
+  while (true) {
+    if (suffix != 0) {
+      Name.append("_");
+      Name.append(llvm::Twine(suffix).str());
+      II = &AST.Idents.get(Name, tok::TokenKind::identifier);
+    }
+    if (!findRecordDeclInContext(II, BaseDecl->getDeclContext()))
+      return II;
+    // declaration with that name already exists - increment suffix and try
+    // again until unique name is found
+    suffix++;
+    Name.truncate(NameLength);
+  };
+}
+
+// Creates a field declaration of given name and type for HLSL buffer layout
+// struct. Returns nullptr if the type cannot be use in HLSL Buffer layout.
+static FieldDecl *createFieldForHostLayoutStruct(Sema &S, const Type *Ty,
+                                                 IdentifierInfo *II,
+                                                 CXXRecordDecl *LayoutStruct) {
+  if (isInvalidConstantBufferLeafElementType(Ty))
+    return nullptr;
+
+  if (Ty->isRecordType()) {
+    CXXRecordDecl *RD = Ty->getAsCXXRecordDecl();
+    if (requiresImplicitBufferLayoutStructure(RD)) {
+      RD = createHostLayoutStruct(S, RD);
+      if (!RD)
+        return nullptr;
+      Ty = RD->getTypeForDecl();
+    }
+  }
+
+  QualType QT = QualType(Ty, 0);
+  ASTContext &AST = S.getASTContext();
+  TypeSourceInfo *TSI = AST.getTrivialTypeSourceInfo(QT, SourceLocation());
+  auto *Field = FieldDecl::Create(AST, LayoutStruct, SourceLocation(),
+                                  SourceLocation(), II, QT, TSI, nullptr, false,
+                                  InClassInitStyle::ICIS_NoInit);
+  Field->setAccess(AccessSpecifier::AS_private);
+  return Field;
+}
+
+// Creates host layout struct for a struct included in HLSL Buffer.
+// The layout struct will include only fields that are allowed in HLSL buffer.
+// These fields will be filtered out:
+// - resource classes
+// - empty structs
+// - zero-sized arrays
+// Returns nullptr if the resulting layout struct would be empty.
+static CXXRecordDecl *createHostLayoutStruct(Sema &S,
+                                             CXXRecordDecl *StructDecl) {
+  assert(requiresImplicitBufferLayoutStructure(StructDecl) &&
+         "struct is already HLSL buffer compatible");
+
+  ASTContext &AST = S.getASTContext();
+  DeclContext *DC = StructDecl->getDeclContext();
+  IdentifierInfo *II = getHostLayoutStructName(S, StructDecl, false);
+
+  // reuse existing if the layout struct if it already exists
+  if (CXXRecordDecl *RD = findRecordDeclInContext(II, DC))
+    return RD;
+
+  CXXRecordDecl *LS = CXXRecordDecl::Create(
+      AST, TagDecl::TagKind::Class, DC, SourceLocation(), SourceLocation(), II);
+  LS->setImplicit(true);
+  LS->startDefinition();
+
+  // copy base struct, create HLSL Buffer compatible version if needed
+  if (unsigned NumBases = StructDecl->getNumBases()) {
+    assert(NumBases == 1 && "HLSL supports only one base type");
+    CXXBaseSpecifier Base = *StructDecl->bases_begin();
+    CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
+    if (requiresImplicitBufferLayoutStructure(BaseDecl)) {
+      BaseDecl = createHostLayoutStruct(S, BaseDecl);
+      if (BaseDecl) {
+        TypeSourceInfo *TSI = AST.getTrivialTypeSourceInfo(
+            QualType(BaseDecl->getTypeForDecl(), 0));
+        Base = CXXBaseSpecifier(SourceRange(), false, StructDecl->isClass(),
+                                AS_none, TSI, SourceLocation());
+      }
+    }
+    if (BaseDecl) {
+      const CXXBaseSpecifier *BasesArray[1] = {&Base};
+      LS->setBases(BasesArray, 1);
+    }
+  }
+
+  // filter struct fields
+  for (const FieldDecl *FD : StructDecl->fields()) {
+    const Type *Ty = FD->getType()->getUnqualifiedDesugaredType();
+    if (FieldDecl *NewFD =
+            createFieldForHostLayoutStruct(S, Ty, FD->getIdentifier(), LS))
+      LS->addDecl(NewFD);
+  }
+  LS->completeDefinition();
+
+  if (LS->field_empty() && LS->getNumBases() == 0)
+    return nullptr;
+
+  DC->addDecl(LS);
+  return LS;
+}
+
+// Creates host layout struct for HLSL Buffer. The struct will include only
+// fields of types that are allowed in HLSL buffer and it will filter out:
+// - static variable declarations
+// - resource classes
+// - empty structs
+// - zero-sized arrays
+// - non-variable declarations
+// The layour struct will be added to the HLSLBufferDecl declarations.
+void createHostLayoutStructForBuffer(Sema &S, HLSLBufferDecl *BufDecl) {
+  ASTContext &AST = S.getASTContext();
+  IdentifierInfo *II = getHostLayoutStructName(S, BufDecl, true);
+
+  CXXRecordDecl *LS =
+      CXXRecordDecl::Create(AST, TagDecl::TagKind::Class, BufDecl,
+                            SourceLocation(), SourceLocation(), II);
+  LS->setImplicit(true);
+  LS->startDefinition();
+
+  for (const Decl *D : BufDecl->decls()) {
+    const VarDecl *VD = dyn_cast<VarDecl>(D);
+    if (!VD || VD->getStorageClass() == SC_Static)
+      continue;
+    const Type *Ty = VD->getType()->getUnqualifiedDesugaredType();
+    if (FieldDecl *FD =
+            createFieldForHostLayoutStruct(S, Ty, VD->getIdentifier(), LS))
+      LS->addDecl(FD);
+  }
+  LS->completeDefinition();
+  BufDecl->addDecl(LS);
+}
+
+// Handle end of cbuffer/tbuffer declaration
 void SemaHLSL::ActOnFinishBuffer(Decl *Dcl, SourceLocation RBrace) {
   auto *BufDecl = cast<HLSLBufferDecl>(Dcl);
   BufDecl->setRBraceLoc(RBrace);
 
   validatePackoffset(SemaRef, BufDecl);
 
+  // create buffer layout struct
+  createHostLayoutStructForBuffer(SemaRef, BufDecl);
+
   SemaRef.PopDeclContext();
 }
 

clang/test/AST/HLSL/ast-dump-comment-cbuffe-tbufferr.hlsl renamed to clang/test/AST/HLSL/ast-dump-comment-cbuffer-tbuffer.hlsl

@@ -37,19 +37,26 @@ tbuffer B {
     int d;
 }
 
-// AST:HLSLBufferDecl {{.*}}:11:1, line:20:1> line:11:9 cbuffer A
-// AST-NEXT:-HLSLResourceClassAttr {{.*}} <<invalid sloc>> Implicit CBuffer
-// AST-NEXT:-HLSLResourceAttr {{.*}} <<invalid sloc>> Implicit CBuffer
-// AST-NEXT:FullComment {{.*}}<line:10:4, col:17>
-// AST-NEXT:`-ParagraphComment {{.*}}<col:4, col:17>
-// AST-NEXT:`-TextComment {{.*}}<col:4, col:17> Text=" CBuffer decl."
-// AST-NEXT:-VarDecl {{.*}}<line:15:5, col:11> col:11 a 'float'
-// AST-NEXT:`-VarDecl {{.*}}<line:19:5, col:9> col:9 b 'int'
-// AST-NEXT:HLSLBufferDecl {{.*}}<line:29:1, line:38:1> line:29:9 tbuffer B
-// AST-NEXT:-HLSLResourceClassAttr {{.*}} <<invalid sloc>> Implicit SRV
-// AST-NEXT:-HLSLResourceAttr {{.*}} <<invalid sloc>> Implicit TBuffer
-// AST-NEXT:-FullComment {{.*}}<line:28:4, col:17>
-// AST-NEXT: `-ParagraphComment {{.*}}<col:4, col:17>
-// AST-NEXT:  `-TextComment {{.*}}<col:4, col:17> Text=" TBuffer decl."
-// AST-NEXT:-VarDecl {{.*}}<line:33:5, col:11> col:11 c 'float'
-// AST-NEXT:`-VarDecl {{.*}} <line:37:5, col:9> col:9 d 'int'
+// AST: HLSLBufferDecl {{.*}} line:11:9 cbuffer A
+// AST-NEXT: HLSLResourceClassAttr {{.*}} Implicit CBuffer
+// AST-NEXT: HLSLResourceAttr {{.*}} Implicit CBuffer
+// AST-NEXT: FullComment
+// AST-NEXT: ParagraphComment
+// AST-NEXT: TextComment {{.*}} Text=" CBuffer decl."
+// AST-NEXT: VarDecl {{.*}} a 'float'
+// AST-NEXT: VarDecl {{.*}} b 'int'
+// AST-NEXT: CXXRecordDecl {{.*}} implicit class __layout_A definition
+// AST: FieldDecl {{.*}} a 'float'
+// AST-NEXT: FieldDecl {{.*}} b 'int'
+
+// AST-NEXT: HLSLBufferDecl {{.*}} line:29:9 tbuffer B
+// AST-NEXT: HLSLResourceClassAttr {{.*}} Implicit SRV
+// AST-NEXT: HLSLResourceAttr {{.*}} Implicit TBuffer
+// AST-NEXT: FullComment
+// AST-NEXT: ParagraphComment
+// AST-NEXT: TextComment {{.*}} Text=" TBuffer decl."
+// AST-NEXT: VarDecl {{.*}} c 'float'
+// AST-NEXT: VarDecl {{.*}} d 'int'
+// AST-NEXT: CXXRecordDecl {{.*}} implicit class __layout_B definition
+// AST: FieldDecl {{.*}} c 'float'
+// AST-NEXT: FieldDecl {{.*}} d 'int'