[HLSL] Enable unbounded resource arrays at global scope (llvm#155053)

Adds support for unbounded resource arrays declared at a global scope. Local unbounded resource array variables or incomplete resource arrays as function arguments are not going be supported in HLSL in Clang. See:
 - microsoft/hlsl-specs#141
 - llvm/wg-hlsl#298

Closes llvm#145427

Author: hekota

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -13205,6 +13205,9 @@ def err_hlsl_resource_range_overlap: Error<
   "%select{All|Vertex|Hull|Domain|Geometry|Pixel|Amplification|Mesh}9">;
 def note_hlsl_resource_range_here: Note<"overlapping resource range here">;
 
+def err_hlsl_incomplete_resource_array_in_function_param: Error<
+  "incomplete resource array in a function parameter">;
+
 // Layout randomization diagnostics.
 def err_non_designated_init_used : Error<
   "a randomized struct can only be initialized with a designated initializer">;

clang/lib/AST/Type.cpp

@@ -5420,7 +5420,7 @@ bool Type::isHLSLResourceRecordArray() const {
   const Type *Ty = getUnqualifiedDesugaredType();
   if (!Ty->isArrayType())
     return false;
-  while (isa<ConstantArrayType>(Ty))
+  while (isa<ArrayType>(Ty))
     Ty = Ty->getArrayElementTypeNoTypeQual();
   return Ty->isHLSLResourceRecord();
 }
@@ -5433,7 +5433,7 @@ bool Type::isHLSLIntangibleType() const {
     return Ty->isHLSLBuiltinIntangibleType();
 
   // unwrap arrays
-  while (isa<ConstantArrayType>(Ty))
+  while (isa<ArrayType>(Ty))
     Ty = Ty->getArrayElementTypeNoTypeQual();
 
   const RecordType *RT =

clang/lib/Sema/SemaDecl.cpp

@@ -14393,9 +14393,12 @@ void Sema::ActOnUninitializedDecl(Decl *RealDecl) {
       return;
     }
 
-    // Provide a specific diagnostic for uninitialized variable
-    // definitions with incomplete array type.
-    if (Type->isIncompleteArrayType()) {
+    // Provide a specific diagnostic for uninitialized variable definitions
+    // with incomplete array type, unless it is a global unbounded HLSL resource
+    // array.
+    if (Type->isIncompleteArrayType() &&
+        !(getLangOpts().HLSL && Var->hasGlobalStorage() &&
+          Type->isHLSLResourceRecordArray())) {
       if (Var->isConstexpr())
         Diag(Var->getLocation(), diag::err_constexpr_var_requires_const_init)
             << Var;
@@ -15476,6 +15479,14 @@ Decl *Sema::ActOnParamDeclarator(Scope *S, Declarator &D,
     }
   }
 
+  // Incomplete resource arrays are not allowed as function parameters in HLSL
+  if (getLangOpts().HLSL && parmDeclType->isIncompleteArrayType() &&
+      parmDeclType->isHLSLResourceRecordArray()) {
+    Diag(D.getIdentifierLoc(),
+         diag::err_hlsl_incomplete_resource_array_in_function_param);
+    D.setInvalidType(true);
+  }
+
   // Temporarily put parameter variables in the translation unit, not
   // the enclosing context.  This prevents them from accidentally
   // looking like class members in C++.

clang/lib/Sema/SemaHLSL.cpp

@@ -350,8 +350,8 @@ getResourceArrayHandleType(VarDecl *VD) {
   assert(VD->getType()->isHLSLResourceRecordArray() &&
          "expected array of resource records");
   const Type *Ty = VD->getType()->getUnqualifiedDesugaredType();
-  while (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(Ty))
-    Ty = CAT->getArrayElementTypeNoTypeQual()->getUnqualifiedDesugaredType();
+  while (const ArrayType *AT = dyn_cast<ArrayType>(Ty))
+    Ty = AT->getArrayElementTypeNoTypeQual()->getUnqualifiedDesugaredType();
   return HLSLAttributedResourceType::findHandleTypeOnResource(Ty);
 }
 
@@ -2022,9 +2022,11 @@ static bool DiagnoseHLSLRegisterAttribute(Sema &S, SourceLocation &ArgLoc,
 }
 
 void SemaHLSL::handleResourceBindingAttr(Decl *TheDecl, const ParsedAttr &AL) {
-  if (isa<VarDecl>(TheDecl)) {
-    if (SemaRef.RequireCompleteType(TheDecl->getBeginLoc(),
-                                    cast<ValueDecl>(TheDecl)->getType(),
+  if (VarDecl *VD = dyn_cast<VarDecl>(TheDecl)) {
+    QualType Ty = VD->getType();
+    if (const auto *IAT = dyn_cast<IncompleteArrayType>(Ty))
+      Ty = IAT->getElementType();
+    if (SemaRef.RequireCompleteType(TheDecl->getBeginLoc(), Ty,
                                     diag::err_incomplete_type))
       return;
   }
@@ -3831,9 +3833,9 @@ void SemaHLSL::collectResourceBindingsOnVarDecl(VarDecl *VD) {
   // Unwrap arrays
   // FIXME: Calculate array size while unwrapping
   const Type *Ty = VD->getType()->getUnqualifiedDesugaredType();
-  while (Ty->isConstantArrayType()) {
-    const ConstantArrayType *CAT = cast<ConstantArrayType>(Ty);
-    Ty = CAT->getElementType()->getUnqualifiedDesugaredType();
+  while (Ty->isArrayType()) {
+    const ArrayType *AT = cast<ArrayType>(Ty);
+    Ty = AT->getElementType()->getUnqualifiedDesugaredType();
   }
 
   // Resource (or array of resources)

clang/test/CodeGenHLSL/resources/res-array-global-unbounded.hlsl

@@ -0,0 +1,66 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.6-compute -finclude-default-header \
+// RUN:   -emit-llvm -disable-llvm-passes -o - %s | FileCheck %s -check-prefixes=CHECK,DXIL
+// RUN: %clang_cc1 -finclude-default-header -triple spirv-unknown-vulkan-compute \
+// RUN:   -emit-llvm -disable-llvm-passes -o - %s | FileCheck %s -check-prefixes=CHECK,SPV
+
+// CHECK: @[[BufA:.*]] = private unnamed_addr constant [2 x i8] c"A\00", align 1
+// CHECK: @[[BufB:.*]] = private unnamed_addr constant [2 x i8] c"B\00", align 1
+
+RWBuffer<float> A[] : register(u10, space1);
+RWBuffer<int> B[][5][4];
+
+RWStructuredBuffer<float> Out;
+
+float foo(RWBuffer<int> Arr[4], uint Index) {
+  return (float)Arr[Index][0];
+}
+
+// NOTE:
+// - _ZN4hlsl8RWBufferIfEC1EjjijPKc is the constructor call for explicit binding for RWBuffer<float>
+//    (has "jjij" in the mangled name) and the arguments are (register, space, range_size, index, name).
+// - _ZN4hlsl8RWBufferIiEC1EjijjPKc is the constructor call for implicit binding for RWBuffer<int>
+//    (has "jijj" in the mangled name) and the arguments are (space, range_size, index, order_id, name).
+// - _ZN4hlsl8RWBufferIfEixEj is the subscript operator on RWBuffer<float>
+
+[numthreads(4,1,1)]
+void main(uint GI : SV_GroupIndex) {
+  // CHECK: define internal {{.*}}void @_Z4mainj(i32 noundef %GI)
+  // CHECK: %[[GI_alloca:.*]] = alloca i32, align 4
+  // CHECK-NEXT: %a = alloca float, align 4
+  // CHECK-NEXT: %[[Tmp0:.*]] = alloca %"class.hlsl::RWBuffer
+  // CHECK-NEXT: %b = alloca float, align 4
+  // CHECK-NEXT: %[[Tmp1:.*]] = alloca [4 x %"class.hlsl::RWBuffer"]
+  // CHECK-NEXT: %[[Tmp2:.*]] = alloca [4 x %"class.hlsl::RWBuffer"]
+  // CHECK-NEXT: store i32 %GI, ptr %[[GI_alloca]], align 4
+
+  // Make sure A[100] is translated to a RWBuffer<float> constructor call with range -1 and index 100
+  // and explicit binding (u10, space1) 
+  // CHECK: call void @_ZN4hlsl8RWBufferIfEC1EjjijPKc(ptr {{.*}} %[[Tmp0]], i32 noundef 10, i32 noundef 1, i32 noundef -1, i32 noundef 100, ptr noundef @A.str)
+  // CHECK-NEXT: %[[BufPtr:.*]] = call {{.*}} ptr{{.*}} @_ZN4hlsl8RWBufferIfEixEj(ptr {{.*}} %[[Tmp0]], i32 noundef 0)
+  // CHECK-NEXT: %[[Value1:.*]] = load float, ptr{{.*}} %[[BufPtr]], align 4
+  // CHECK-NEXT: store float %[[Value1]], ptr %a, align 4
+  float a = A[100][0];
+
+  // Make sure B[2][3] is translated to a local RWBuffer<int>[4] array where each array element
+  // is initialized by a constructor call with range -1 and index 52-55 and implicit binding 
+  // (space 0, order_id 0) 
+  // The first index is calculated from the array dimensions (unbounded x 5 x 4) and indices (2, 3)
+  // as 2 * 5 * 4 + 3 * 4 = 52 and the following indices are sequential.
+  // CHECK-NEXT: %[[Ptr_Tmp2_0:.*]] = getelementptr [4 x %"class.hlsl::RWBuffer"], ptr %[[Tmp2]], i32 0, i32 0
+  // CHECK-NEXT: call void @_ZN4hlsl8RWBufferIiEC1EjijjPKc(ptr {{.*}} %[[Ptr_Tmp2_0]], i32 noundef 0, i32 noundef -1, i32 noundef 52, i32 noundef 0, ptr noundef @B.str)
+  // CHECK-NEXT: %[[Ptr_Tmp2_1:.*]] = getelementptr [4 x %"class.hlsl::RWBuffer"], ptr %[[Tmp2]], i32 0, i32 1
+  // CHECK-NEXT: call void @_ZN4hlsl8RWBufferIiEC1EjijjPKc(ptr {{.*}} %[[Ptr_Tmp2_1]], i32 noundef 0, i32 noundef -1, i32 noundef 53, i32 noundef 0, ptr noundef @B.str)
+  // CHECK-NEXT: %[[Ptr_Tmp2_2:.*]] = getelementptr [4 x %"class.hlsl::RWBuffer"], ptr %[[Tmp2]], i32 0, i32 2
+  // CHECK-NEXT: call void @_ZN4hlsl8RWBufferIiEC1EjijjPKc(ptr {{.*}} %[[Ptr_Tmp2_2]], i32 noundef 0, i32 noundef -1, i32 noundef 54, i32 noundef 0, ptr noundef @B.str)
+  // CHECK-NEXT: %[[Ptr_Tmp2_3:.*]] = getelementptr [4 x %"class.hlsl::RWBuffer"], ptr %[[Tmp2]], i32 0, i32 3
+  // CHECK-NEXT: call void @_ZN4hlsl8RWBufferIiEC1EjijjPKc(ptr {{.*}} %[[Ptr_Tmp2_3]], i32 noundef 0, i32 noundef -1, i32 noundef 55, i32 noundef 0, ptr noundef @B.str)
+  // DXIL-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 4 %[[Tmp1]], ptr align 4 %[[Tmp2]], i32 16, i1 false)
+  // SPV-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[Tmp1]], ptr align 8 %[[Tmp2]], i64 32, i1 false)
+  // CHECK-NEXT: %[[GI:.*]] = load i32, ptr %[[GI_alloca]], align 4
+  // DXIL-NEXT: %[[Value2:.*]] = call {{.*}} float @_Z3fooA4_N4hlsl8RWBufferIiEEj(ptr noundef byval([4 x %"class.hlsl::RWBuffer"]) align 4 %[[Tmp1]], i32 noundef %[[GI]])
+  // SPV-NEXT: %[[Value2:.*]] = call {{.*}} float @_Z3fooA4_N4hlsl8RWBufferIiEEj(ptr noundef byval([4 x %"class.hlsl::RWBuffer"]) align 8 %[[Tmp1]], i32 noundef %[[GI]])
+  // CHECK-NEXT: store float %[[Value2]], ptr %b, align 4
+  float b = foo(B[2][3], GI);
+
+  Out[0] = a + b;
+}

clang/test/SemaHLSL/unbounded_resource_arrays.hlsl

@@ -0,0 +1,21 @@
+// RUN: not %clang_cc1 -triple dxil-pc-shadermodel6.3-compute -finclude-default-header --o - %s -verify
+
+// unbounded resource array at a global scope
+RWBuffer<float> unbounded_array[]; // no_error
+
+// expected-error@+1 {{incomplete resource array in a function parameter}}
+void foo(RWBuffer<float> array_arg[]) {}
+
+RWBuffer<float> A, B;
+
+[numthreads(4,1,1)]
+void main() {
+  // expected-error@+1{{definition of variable with array type needs an explicit size or an initializer}}
+  RWBuffer<float> res_local_array1[]; 
+
+  // expected-error@+1{{array initializer must be an initialzer list}}
+  RWBuffer<float> res_local_array2[] = unbounded_array;
+
+  // local incomplete resource array with initializer
+  RWBuffer<float> res_local_array3[] = { A, B }; // no error
+}