Disallow built-in internal types to be inferred by auto (#8510)

This patch adds the check into SemaDecl to disallow auto to infer
built-in internal types, like `sample_type` and `mip_type`. And
Subobject types, like the ones used in DXR.

---------

Co-authored-by: Chris B <beanz@abolishcrlf.org>
Co-authored-by: Tex Riddell <texr@microsoft.com>

Author: 3 people

tools/clang/include/clang/Basic/Attr.td

@@ -1188,6 +1188,15 @@ def HLSLSubObject : InheritableAttr {
   let Args = [UnsignedArgument<"SubObjKindUint">, UnsignedArgument<"HitGroupType">];
 }
 
+// Marks builtin record types that have no deducible value form, so 'auto' must
+// not infer them: the inner indexer objects behind .mips / .sample, and the
+// subobject types used to configure DXR state objects.
+def HLSLNonAutoDeducible : InheritableAttr {
+  let Spellings = []; // No spellings!
+  let Subjects = SubjectList<[CXXRecord]>;
+  let Documentation = [Undocumented];
+}
+
 // HLSL HitObject Attribute
 
 def HLSLHitObject : InheritableAttr {

tools/clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -8070,6 +8070,9 @@ def err_hlsl_auto_descriptor_heap : Error<
   "'auto' cannot deduce the type of '%select{ResourceDescriptorHeap|SamplerDescriptorHeap}0'; "
   "use a specific resource or sampler type instead">;
 
+def err_hlsl_auto_undeducible_type : Error<
+  "'auto' cannot deduce type %0">;
+
 // HLSL Change Ends
 
 // SPIRV Change Starts

tools/clang/include/clang/Sema/SemaHLSL.h

@@ -93,6 +93,10 @@ bool DiagnoseTypeElements(clang::Sema &S, clang::SourceLocation Loc,
                           TypeDiagContext LongVecDiagContext,
                           const clang::FieldDecl *FD = nullptr);
 
+// Returns true if 'auto' is allowed to deduce the given type. Container types
+// are deducible only when the type they wrap is deducible.
+bool IsTypeDeducibleWithAuto(clang::Sema &S, clang::QualType Ty);
+
 void DiagnoseControlFlowConditionForHLSL(clang::Sema *self,
                                          clang::Expr *condExpr,
                                          llvm::StringRef StmtName);

tools/clang/lib/Sema/SemaDecl.cpp

@@ -9051,6 +9051,16 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init,
         VDecl->setInvalidDecl();
         return;
       }
+
+      // A dependent deduced type cannot be classified yet; defer the check to
+      // instantiation, when 'auto' is re-deduced to a concrete type.
+      if (!DeducedType->isDependentType() &&
+          !hlsl::IsTypeDeducibleWithAuto(*this, DeducedType)) {
+        Diag(VDecl->getLocation(), diag::err_hlsl_auto_undeducible_type)
+            << DeducedType;
+        VDecl->setInvalidDecl();
+        return;
+      }
     }
 
     VDecl->setType(DeducedType);

tools/clang/lib/Sema/SemaHLSL.cpp

@@ -3007,6 +3007,7 @@ StartSubobjectDecl(ASTContext &context, const char *name,
       NoLoc, &id, nullptr, DelayTypeCreationTrue);
   decl->addAttr(HLSLSubObjectAttr::CreateImplicit(
       context, static_cast<unsigned>(Kind), static_cast<unsigned>(HGT)));
+  decl->addAttr(HLSLNonAutoDeducibleAttr::CreateImplicit(context));
   decl->addAttr(FinalAttr::CreateImplicit(context, FinalAttr::Keyword_final));
   decl->startDefinition();
   return decl;
@@ -3528,6 +3529,8 @@ class HLSLExternalSource : public ExternalSemaSource {
                               &m_context->Idents.get(StringRef(type1Name)));
     sampleSliceTypeDecl->setAccess(AS_public);
     sampleSliceTypeDecl->setImplicit();
+    sampleSliceTypeDecl->addAttr(
+        HLSLNonAutoDeducibleAttr::CreateImplicit(*m_context));
     recordDecl->addDecl(sampleSliceTypeDecl);
     sampleSliceTypeDecl->startDefinition();
     const bool MutableFalse = false;
@@ -3556,6 +3559,8 @@ class HLSLExternalSource : public ExternalSemaSource {
     recordDecl->addDecl(sampleTypeDecl);
     sampleTypeDecl->startDefinition();
     sampleTypeDecl->setImplicit();
+    sampleTypeDecl->addAttr(
+        HLSLNonAutoDeducibleAttr::CreateImplicit(*m_context));
 
     FieldDecl *sampleHandleDecl = FieldDecl::Create(
         *m_context, sampleTypeDecl, NoLoc, NoLoc,
@@ -4773,6 +4778,26 @@ class HLSLExternalSource : public ExternalSemaSource {
     return type;
   }
 
+  bool IsTypeDeducibleWithAuto(QualType type) {
+    if (type.isNull())
+      return false;
+
+    if (hlsl::IsStringType(type) || hlsl::IsStringLiteralType(type))
+      return false;
+
+    if (const CXXRecordDecl *recordDecl =
+            GetStructuralForm(type)->getAsCXXRecordDecl()) {
+      if (!recordDecl->hasAttr<HLSLNonAutoDeducibleAttr>())
+        if (const CXXRecordDecl *pattern =
+                recordDecl->getTemplateInstantiationPattern())
+          recordDecl = pattern;
+      if (recordDecl->hasAttr<HLSLNonAutoDeducibleAttr>())
+        return false;
+    }
+
+    return true;
+  }
+
   /// <summary>Given a Clang type, return the ArBasicKind classification for its
   /// contents.</summary>
   ArBasicKind GetTypeElementKind(QualType type) {
@@ -12787,6 +12812,10 @@ bool hlsl::DiagnoseTypeElements(Sema &S, SourceLocation Loc, QualType Ty,
                               LongVecDiagContext, CheckedDecls, FD);
 }
 
+bool hlsl::IsTypeDeducibleWithAuto(Sema &S, QualType Ty) {
+  return HLSLExternalSource::FromSema(&S)->IsTypeDeducibleWithAuto(Ty);
+}
+
 bool hlsl::DiagnoseNodeStructArgument(Sema *self, TemplateArgumentLoc ArgLoc,
                                       QualType ArgTy, bool &Empty,
                                       const FieldDecl *FD) {

tools/clang/test/HLSLFileCheckLit/hlsl/auto/auto-deducible-types.hlsl

@@ -0,0 +1,40 @@
+// RUN: %dxc -T cs_6_0 -HV 202x -verify %s
+// expected-no-diagnostics
+
+struct MyStruct {
+    float a;
+    int b;
+};
+
+Texture2D<float4> tex : register(t0);
+SamplerState samp : register(s0);
+RWBuffer<float> output : register(u0);
+
+[numthreads(1,1,1)]
+void main() {
+    // Scalars.
+    auto i = 5;
+    auto f = 1.5f;
+    auto b = true;
+
+    // Vectors.
+    auto v = float4(1, 2, 3, 4);
+
+
+    // Matrices.
+    float2x2 matInit = { 1, 2, 3, 4 };
+    auto m = matInit;
+    auto row = m[0];
+    auto elem = m[0][0];
+
+    // User-defined structs.
+    MyStruct s = { 1.0f, 2 };
+    auto sCopy = s;
+
+    // Resource objects (their handles are copyable, so binding one is allowed).
+    auto t = tex;
+
+    // Use every value to prevent dead-code elimination.
+    output[0] = (float)i + f + (float)b + v.x + m._11 + row.x + elem + sCopy.a +
+                (float)sCopy.b + t.SampleLevel(samp, float2(0, 0), 0).x;
+}

tools/clang/test/HLSLFileCheckLit/hlsl/auto/auto-no-subobject.hlsl

@@ -0,0 +1,32 @@
+// RUN: %dxc -T lib_6_3 -HV 202x -verify %s
+
+GlobalRootSignature grs = {"CBV(b0)"};
+LocalRootSignature lrs = {"UAV(u0)"};
+StateObjectConfig soc = { STATE_OBJECT_FLAGS_ALLOW_LOCAL_DEPENDENCIES_ON_EXTERNAL_DEFINITONS };
+SubobjectToExportsAssociation sea = { "grs", "a;b" };
+RaytracingShaderConfig rsc = { 128, 64 };
+RaytracingPipelineConfig rpc = { 512 };
+RaytracingPipelineConfig1 rpc1 = { 32, RAYTRACING_PIPELINE_FLAG_ALLOW_OPACITY_MICROMAPS };
+TriangleHitGroup trHitGt = { "a", "b" };
+ProceduralPrimitiveHitGroup ppHitGt = { "a", "b", "c" };
+
+void useSubobjects() {
+    // expected-error@+1 {{'auto' cannot deduce type 'GlobalRootSignature'}}
+    auto a = grs;
+    // expected-error@+1 {{'auto' cannot deduce type 'LocalRootSignature'}}
+    auto b = lrs;
+    // expected-error@+1 {{'auto' cannot deduce type 'StateObjectConfig'}}
+    auto c = soc;
+    // expected-error@+1 {{'auto' cannot deduce type 'SubobjectToExportsAssociation'}}
+    auto d = sea;
+    // expected-error@+1 {{'auto' cannot deduce type 'RaytracingShaderConfig'}}
+    auto e = rsc;
+    // expected-error@+1 {{'auto' cannot deduce type 'RaytracingPipelineConfig'}}
+    auto f = rpc;
+    // expected-error@+1 {{'auto' cannot deduce type 'RaytracingPipelineConfig1'}}
+    auto g = rpc1;
+    // expected-error@+1 {{'auto' cannot deduce type 'TriangleHitGroup'}}
+    auto h = trHitGt;
+    // expected-error@+1 {{'auto' cannot deduce type 'ProceduralPrimitiveHitGroup'}}
+    auto i = ppHitGt;
+}

tools/clang/test/HLSLFileCheckLit/hlsl/auto/auto-undeducible-types.hlsl

@@ -0,0 +1,35 @@
+// RUN: %dxc -T cs_6_0 -HV 202x -verify %s
+
+
+void voidFunc() {}
+
+Texture2D<float4> tex : register(t0);
+Texture2DMS<float4> texMS : register(t1);
+
+[numthreads(1,1,1)]
+void main() {
+    int y = 1;
+
+    // expected-error@+1 {{'auto' cannot deduce type}}
+    auto str = "abc";
+
+    // expected-error@+1 {{variable has incomplete type 'void'}}
+    auto x = voidFunc();
+
+    // expected-error@+1 {{variable has incomplete type 'void'}}
+    auto v = (void)y;
+
+    // expected-error@+1 {{'auto' cannot deduce type}}
+    auto m = tex.mips;
+    // expected-error@+1 {{'auto' cannot deduce type}}
+    auto m2 = tex.mips[0];
+    // legal: load float4 from mip 0
+    auto m3 = tex.mips[0][int2(1,2)];
+
+    // expected-error@+1 {{'auto' cannot deduce type}}
+    auto s = texMS.sample;
+    // expected-error@+1 {{'auto' cannot deduce type}}
+    auto s2 = texMS.sample[0];
+    // legal: load float4 from sample 0
+    auto s3 = texMS.sample[0][int2(1,2)];
+}

tools/clang/test/SemaHLSL/inner-object-ast-dump.hlsl

@@ -0,0 +1,27 @@
+// RUN: %dxc -T ps_6_0 -ast-dump-implicit %s | FileCheck %s
+
+// This test verifies that the inner indexer object types backing .mips and
+// .sample (mips_type / mips_slice_type, sample_type / sample_slice_type) carry
+// the implicit HLSLNonAutoDeducibleAttr, so that 'auto' cannot deduce them.
+// See also subobjects-ast-dump.hlsl, which checks the same attribute on
+// subobject types.
+
+Texture2D<float4> srv;
+Texture2DMS<float4> srvMS;
+
+float4 main() : SV_Target {
+  return 0;
+}
+
+// The slice type is created before the indexer type, so it is dumped first;
+// each carries the attribute as its first child. Texture2D (.mips) is referenced
+// before Texture2DMS (.sample), so the mips records are dumped first.
+
+// CHECK: CXXRecordDecl {{0x[0-9a-fA-F]+}} <<invalid sloc>> <invalid sloc> implicit {{.*}}mips_slice_type definition
+// CHECK-NEXT: HLSLNonAutoDeducibleAttr {{0x[0-9a-fA-F]+}} <<invalid sloc>> Implicit
+// CHECK: CXXRecordDecl {{0x[0-9a-fA-F]+}} <<invalid sloc>> <invalid sloc> implicit {{.*}}mips_type definition
+// CHECK-NEXT: HLSLNonAutoDeducibleAttr {{0x[0-9a-fA-F]+}} <<invalid sloc>> Implicit
+// CHECK: CXXRecordDecl {{0x[0-9a-fA-F]+}} <<invalid sloc>> <invalid sloc> implicit {{.*}}sample_slice_type definition
+// CHECK-NEXT: HLSLNonAutoDeducibleAttr {{0x[0-9a-fA-F]+}} <<invalid sloc>> Implicit
+// CHECK: CXXRecordDecl {{0x[0-9a-fA-F]+}} <<invalid sloc>> <invalid sloc> implicit {{.*}}sample_type definition
+// CHECK-NEXT: HLSLNonAutoDeducibleAttr {{0x[0-9a-fA-F]+}} <<invalid sloc>> Implicit

tools/clang/test/SemaHLSL/subobjects-ast-dump.hlsl

@@ -8,43 +8,52 @@
 
 // ASTIMPL: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct StateObjectConfig definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 0 2
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit Flags 'unsigned int'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct GlobalRootSignature definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 1 2
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit Data 'string'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct LocalRootSignature definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 2 2
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit Data 'string'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct SubobjectToExportsAssociation definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 8 2
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit Subobject 'string'
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit Exports 'string'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct RaytracingShaderConfig definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 9 2
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit MaxPayloadSizeInBytes 'unsigned int'
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit MaxAttributeSizeInBytes 'unsigned int'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit struct RaytracingPipelineConfig definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 10 2
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit MaxTraceRecursionDepth 'unsigned int'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct TriangleHitGroup definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 11 0
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit AnyHit 'string'
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit ClosestHit 'string'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct ProceduralPrimitiveHitGroup definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 11 1
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit AnyHit 'string'
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit ClosestHit 'string'
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit Intersection 'string'
 // ASTIMPL-NEXT: CXXRecordDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit referenced struct RaytracingPipelineConfig1 definition
 // ASTIMPL-NEXT: HLSLSubObjectAttr 0x{{.+}} <<invalid sloc>> Implicit 12 2
+// ASTIMPL-NEXT: HLSLNonAutoDeducibleAttr 0x{{.+}} <<invalid sloc>> Implicit
 // ASTIMPL-NEXT: FinalAttr 0x{{.+}} <<invalid sloc>> Implicit final
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit MaxTraceRecursionDepth 'unsigned int'
 // ASTIMPL-NEXT: FieldDecl 0x{{.+}} <<invalid sloc>> <invalid sloc> implicit Flags 'unsigned int'