[clang] [HLSL] cbuffer: Create host layout structs (PR #122820)

[Tex Riddell via cfe-commits]

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@@ -253,12 +257,229 @@ 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 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 (Ty->isRecordType()) {
+      if (requiresImplicitBufferLayoutStructure(Ty->getAsCXXRecordDecl()))
+        return true;
+    } else if (Ty->isConstantArrayType()) {
+      if (isZeroSizedArray(cast<ConstantArrayType>(Ty)))
+        return true;
+    }
+  }
+  // check bases
+  for (const CXXBaseSpecifier &Base : RD->bases())
+    if (requiresImplicitBufferLayoutStructure(
+            Base.getType()->getAsCXXRecordDecl()))
+      return true;
+  return false;
+}
+
+static CXXRecordDecl *findRecordDecl(Sema &S, IdentifierInfo *II,
+                                     DeclContext *DC) {
+  DeclarationNameInfo NameInfo =
+      DeclarationNameInfo(DeclarationName(II), SourceLocation());
+  LookupResult R(S, NameInfo, Sema::LookupOrdinaryName);
+  S.LookupName(R, S.getScopeForContext(DC));
+  if (R.isSingleResult())
+    return R.getAsSingle<CXXRecordDecl>();
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tex3d wrote:

Could this be multiple results if the name is defined in multiple accessible scopes (like current and parent scopes)?  Or does it only return zero or one result from the specified scope?

https://github.com/llvm/llvm-project/pull/122820