Implement GL_EXT_null_initializer

Adds null initializer syntax (empty braces)
Allows null initialization of shared variables

SPIRV/GlslangToSpv.cpp

@@ -3652,13 +3652,14 @@ spv::Id TGlslangToSpvTraverser::createSpvVariable(const glslang::TIntermSymbol*
 
     spv::Id initializer = spv::NoResult;
 
-    if (node->getType().getQualifier().storage == glslang::EvqUniform &&
+    if (node->getType().getQualifier().storage == glslang::EvqUniform && !node->getConstArray().empty()) {
-        !node->getConstArray().empty()) {
+        int nextConst = 0;
-            int nextConst = 0;
+        initializer = createSpvConstantFromConstUnionArray(node->getType(),
-            initializer = createSpvConstantFromConstUnionArray(node->getType(),
+                                                           node->getConstArray(),
-                                                               node->getConstArray(),
+                                                           nextConst,
-                                                               nextConst,
+                                                           false /* specConst */);
-                                                               false /* specConst */);
+    } else if (node->getType().getQualifier().isNullInit()) {
+        initializer = builder.makeNullConstant(spvType);
     }
 
     return builder.createVariable(spv::NoPrecision, storageClass, spvType, name, initializer);

SPIRV/SpvBuilder.cpp

@@ -869,6 +869,30 @@ bool Builder::isSpecConstantOpCode(Op opcode) const
     }
 }
 
+Id Builder::makeNullConstant(Id typeId)
+{
+    Instruction* constant;
+
+    // See if we already made it.
+    Id existing = NoResult;
+    for (int i = 0; i < (int)nullConstants.size(); ++i) {
+        constant = nullConstants[i];
+        if (constant->getTypeId() == typeId)
+            existing = constant->getResultId();
+    }
+
+    if (existing != NoResult)
+        return existing;
+
+    // Make it
+    Instruction* c = new Instruction(getUniqueId(), typeId, OpConstantNull);
+    constantsTypesGlobals.push_back(std::unique_ptr<Instruction>(c));
+    nullConstants.push_back(c);
+    module.mapInstruction(c);
+
+    return c->getResultId();
+}
+
 Id Builder::makeBoolConstant(bool b, bool specConstant)
 {
     Id typeId = makeBoolType();

SPIRV/SpvBuilder.h

@@ -293,6 +293,7 @@ public:
     }
 
     // For making new constants (will return old constant if the requested one was already made).
+    Id makeNullConstant(Id typeId);
     Id makeBoolConstant(bool b, bool specConstant = false);
     Id makeInt8Constant(int i, bool specConstant = false)
         { return makeIntConstant(makeIntType(8),  (unsigned)i, specConstant); }
@@ -838,6 +839,8 @@ public:
     std::unordered_map<unsigned int, std::vector<Instruction*>> groupedStructConstants;
     // map type opcodes to type instructions
     std::unordered_map<unsigned int, std::vector<Instruction*>> groupedTypes;
+    // list of OpConstantNull instructions
+    std::vector<Instruction*> nullConstants;
 
     // stack of switches
     std::stack<Block*> switchMerges;

Test/baseResults/310.comp.out

@@ -9,7 +9,7 @@ ERROR: 0:40: 'in' : global storage input qualifier cannot be used in a compute s
 ERROR: 0:41: 'out' : global storage output qualifier cannot be used in a compute shader 
 ERROR: 0:44: 'shared' : cannot apply layout qualifiers to a shared variable 
 ERROR: 0:44: 'location' : can only apply to uniform, buffer, in, or out storage qualifiers 
-ERROR: 0:45: 'shared' :  cannot initialize this type of qualifier  
+ERROR: 0:45: 'shared' : initializer can only be a null initializer ('{}') 
 ERROR: 0:47: 'local_size' : can only apply to 'in' 
 ERROR: 0:47: 'local_size' : can only apply to 'in' 
 ERROR: 0:47: 'local_size' : can only apply to 'in' 
@@ -115,6 +115,11 @@ ERROR: node is still EOpNull!
 0:36              Constant:
 0:36                1 (const uint)
 0:36            'gl_LocalInvocationIndex' ( in highp uint LocalInvocationIndex)
+0:45  Sequence
+0:45    move second child to first child ( temp highp float)
+0:45      'fs' ( shared highp float)
+0:45      Constant:
+0:45        4.200000
 0:59  Function Definition: foo( ( global void)
 0:59    Function Parameters: 
 0:61    Sequence
@@ -553,6 +558,11 @@ ERROR: node is still EOpNull!
 0:36              Constant:
 0:36                1 (const uint)
 0:36            'gl_LocalInvocationIndex' ( in highp uint LocalInvocationIndex)
+0:45  Sequence
+0:45    move second child to first child ( temp highp float)
+0:45      'fs' ( shared highp float)
+0:45      Constant:
+0:45        4.200000
 0:?   Linker Objects
 0:?     'gl_WorkGroupSize' ( const highp 3-component vector of uint WorkGroupSize)
 0:?       2 (const uint)

Test/baseResults/430.comp.out

@@ -7,7 +7,7 @@ ERROR: 0:44: 'in' : global storage input qualifier cannot be used in a compute s
 ERROR: 0:45: 'out' : global storage output qualifier cannot be used in a compute shader 
 ERROR: 0:48: 'shared' : cannot apply layout qualifiers to a shared variable 
 ERROR: 0:48: 'location' : can only apply to uniform, buffer, in, or out storage qualifiers 
-ERROR: 0:49: 'shared' :  cannot initialize this type of qualifier  
+ERROR: 0:49: 'shared' : initializer can only be a null initializer ('{}') 
 ERROR: 0:52: 'local_size' : cannot change previously set size 
 ERROR: 0:54: 'local_size' : can only apply to 'in' 
 ERROR: 0:54: 'local_size' : can only apply to 'in' 
@@ -52,6 +52,11 @@ ERROR: node is still EOpNull!
 0:39            10 (const int)
 0:39        true case
 0:40        Barrier ( global void)
+0:49  Sequence
+0:49    move second child to first child ( temp float)
+0:49      'fs' ( shared float)
+0:49      Constant:
+0:49        4.200000
 0:66  Function Definition: foo( ( global void)
 0:66    Function Parameters: 
 0:68    Sequence
@@ -184,6 +189,11 @@ ERROR: node is still EOpNull!
 0:39            10 (const int)
 0:39        true case
 0:40        Barrier ( global void)
+0:49  Sequence
+0:49    move second child to first child ( temp float)
+0:49      'fs' ( shared float)
+0:49      Constant:
+0:49        4.200000
 0:?   Linker Objects
 0:?     'gl_WorkGroupSize' ( const 3-component vector of uint WorkGroupSize)
 0:?       2 (const uint)

Test/baseResults/spv.nullInit.comp.out

@@ -0,0 +1,66 @@
+spv.nullInit.comp
+Validation failed
+// Module Version 10000
+// Generated by (magic number): 8000a
+// Id's are bound by 37
+
+                              Capability Shader
+               1:             ExtInstImport  "GLSL.std.450"
+                              MemoryModel Logical GLSL450
+                              EntryPoint GLCompute 4  "main"
+                              ExecutionMode 4 LocalSize 1 1 1
+                              Source GLSL 460
+                              SourceExtension  "GL_EXT_null_initializer"
+                              Name 4  "main"
+                              Name 12  "S"
+                              MemberName 12(S) 0  "v"
+                              MemberName 12(S) 1  "a"
+                              Name 15  "local"
+                              Name 23  "f"
+                              Name 24  "T"
+                              MemberName 24(T) 0  "b"
+                              MemberName 24(T) 1  "s"
+                              Name 27  "t1"
+                              Name 28  "t2"
+                              Name 30  "s"
+                              Name 31  "g"
+                              Name 34  "i"
+                              Name 36  "global"
+               2:             TypeVoid
+               3:             TypeFunction 2
+               6:             TypeFloat 32
+               7:             TypeVector 6(float) 3
+               8:             TypeInt 32 0
+               9:      8(int) Constant 4
+              10:             TypeArray 7(fvec3) 9
+              11:             TypeInt 32 1
+           12(S):             TypeStruct 10 11(int)
+              13:       12(S) ConstantNull
+              14:             TypePointer Function 12(S)
+              16:     11(int) Constant 1
+              17:             TypePointer Function 11(int)
+              21:    6(float) ConstantNull
+              22:             TypePointer Workgroup 6(float)
+           23(f):     22(ptr) Variable Workgroup 21
+           24(T):             TypeStruct 11(int) 12(S)
+              25:       24(T) ConstantNull
+              26:             TypePointer Workgroup 24(T)
+          27(t1):     26(ptr) Variable Workgroup 25
+          28(t2):     26(ptr) Variable Workgroup 25
+              29:             TypePointer Workgroup 12(S)
+           30(s):     29(ptr) Variable Workgroup 13
+           31(g):     22(ptr) Variable Workgroup 21
+              32:     11(int) ConstantNull
+              33:             TypePointer Workgroup 11(int)
+           34(i):     33(ptr) Variable Workgroup 32
+              35:             TypePointer Private 12(S)
+      36(global):     35(ptr) Variable Private 13
+         4(main):           2 Function None 3
+               5:             Label
+       15(local):     14(ptr) Variable Function 13
+              18:     17(ptr) AccessChain 15(local) 16
+              19:     11(int) Load 18
+              20:     11(int) IAdd 19 16
+                              Store 18 20
+                              Return
+                              FunctionEnd

Test/baseResults/vulkan.comp.out

@@ -1,6 +1,17 @@
 vulkan.comp
 ERROR: 0:5: 'local_size' : cannot change previously set size 
-ERROR: 1 compilation errors.  No code generated.
+ERROR: 0:10: 'empty { } initializer' : not supported for this version or the enabled extensions 
+ERROR: 0:15: 'empty { } initializer' : not supported for this version or the enabled extensions 
+ERROR: 0:15: 'initialization with shared qualifier' : not supported for this version or the enabled extensions 
+ERROR: 0:16: 'empty { } initializer' : not supported for this version or the enabled extensions 
+ERROR: 0:26: '{}' : null initializers can't size unsized arrays 
+ERROR: 0:31: 'structure' : non-uniform struct contains a sampler or image: sampVar
+ERROR: 0:31: '{}' : null initializers can't be used on opaque values 
+ERROR: 0:33: 'atomic counter types' : not allowed when using GLSL for Vulkan 
+ERROR: 0:33: 'atomic_uint' : atomic_uints can only be used in uniform variables or function parameters: a
+ERROR: 0:33: '{}' : null initializers can't be used on opaque values 
+ERROR: 0:33: 'atomic_uint' : layout(binding=X) is required 
+ERROR: 12 compilation errors.  No code generated.
 
 
 SPIR-V is not generated for failed compile or link

Test/spv.nullInit.comp

@@ -0,0 +1,32 @@
+#version 460
+
+#extension GL_EXT_null_initializer : enable
+
+#ifdef GL_EXT_null_initializer
+
+struct S {
+    vec3[4] v;
+    int a;
+};
+
+struct T {
+    int b;
+    S s;
+};
+
+shared float f = { };
+shared T t1 = { };
+shared T t2 = { };
+shared S s = { };
+shared float g = { };
+shared int i = { };
+
+void main()
+{
+    S local = { };
+    ++local.a;
+}
+
+S global = { };
+
+#endif

Test/vulkan.comp

@@ -7,6 +7,27 @@ layout(local_size_z_id = 14) in;  // ERROR, can't change this
 void main()
 {
     gl_WorkGroupSize;
+    int i = { };  // ERROR, need an extension
 }
 
 layout(local_size_y_id = 19) in; // ERROR, already used: TODO not yet reported
+
+shared float f = { };  // ERROR, need an extension
+float g = { };         // ERROR, need an extension
+
+#extension GL_EXT_null_initializer : enable
+
+shared float f2 = { };
+float g2 = { };
+
+void foo()
+{
+    int i = { };
+    float fa[] = { };
+}
+
+struct samp {
+    sampler2D s2D;
+} sampVar = { };
+
+atomic_uint a = { };

glslang/Include/Types.h

@@ -499,6 +499,7 @@ public:
         declaredBuiltIn = EbvNone;
 #ifndef GLSLANG_WEB
         noContraction = false;
+        nullInit = false;
 #endif
     }
 
@@ -512,6 +513,7 @@ public:
         clearMemory();
         specConstant = false;
         nonUniform = false;
+        nullInit = false;
         clearLayout();
     }
 
@@ -588,6 +590,8 @@ public:
     bool isNoContraction() const { return false; }
     void setNoContraction() { }
     bool isPervertexNV() const { return false; }
+    void setNullInit() { }
+    bool isNullInit() const { return false; }
 #else
     bool noContraction: 1; // prevent contraction and reassociation, e.g., for 'precise' keyword, and expressions it affects
     bool nopersp      : 1;
@@ -609,6 +613,7 @@ public:
     bool subgroupcoherent  : 1;
     bool shadercallcoherent : 1;
     bool nonprivate   : 1;
+    bool nullInit : 1;
     bool isWriteOnly() const { return writeonly; }
     bool isReadOnly() const { return readonly; }
     bool isRestrict() const { return restrict; }
@@ -644,6 +649,8 @@ public:
     bool isNoContraction() const { return noContraction; }
     void setNoContraction() { noContraction = true; }
     bool isPervertexNV() const { return pervertexNV; }
+    void setNullInit() { nullInit = true; }
+    bool isNullInit() const { return nullInit; }
 #endif
 
     bool isPipeInput() const
@@ -2164,6 +2171,8 @@ public:
             appendStr(" specialization-constant");
         if (qualifier.nonUniform)
             appendStr(" nonuniform");
+        if (qualifier.isNullInit())
+            appendStr(" null-init");
         appendStr(" ");
         appendStr(getStorageQualifierString());
         if (isArray()) {

glslang/MachineIndependent/ParseHelper.cpp

@@ -6815,6 +6815,11 @@ TVariable* TParseContext::declareNonArray(const TSourceLoc& loc, const TString&
 //
 TIntermNode* TParseContext::executeInitializer(const TSourceLoc& loc, TIntermTyped* initializer, TVariable* variable)
 {
+    // A null initializer is an aggregate that hasn't had an op assigned yet
+    // (still EOpNull, no relation to nullInit), and has no children.
+    bool nullInit = initializer->getAsAggregate() && initializer->getAsAggregate()->getOp() == EOpNull &&
+        initializer->getAsAggregate()->getSequence().size() == 0;
+
     //
     // Identifier must be of type constant, a global, or a temporary, and
     // starting at version 120, desktop allows uniforms to have initializers.
@@ -6822,9 +6827,36 @@ TIntermNode* TParseContext::executeInitializer(const TSourceLoc& loc, TIntermTyp
     TStorageQualifier qualifier = variable->getType().getQualifier().storage;
     if (! (qualifier == EvqTemporary || qualifier == EvqGlobal || qualifier == EvqConst ||
            (qualifier == EvqUniform && !isEsProfile() && version >= 120))) {
-        error(loc, " cannot initialize this type of qualifier ", variable->getType().getStorageQualifierString(), "");
+        if (qualifier == EvqShared) {
+            // GL_EXT_null_initializer allows this for shared, if it's a null initializer
+            if (nullInit) {
+                const char* feature = "initialization with shared qualifier";
+                profileRequires(loc, EEsProfile, 0, E_GL_EXT_null_initializer, feature);
+                profileRequires(loc, ~EEsProfile, 0, E_GL_EXT_null_initializer, feature);
+            } else {
+                error(loc, "initializer can only be a null initializer ('{}')", "shared", "");
+            }
+        } else {
+            error(loc, " cannot initialize this type of qualifier ",
+                  variable->getType().getStorageQualifierString(), "");
+            return nullptr;
+        }
+    }
+
+    if (nullInit) {
+        // only some types can be null initialized
+        if (variable->getType().containsUnsizedArray()) {
+            error(loc, "null initializers can't size unsized arrays", "{}", "");
+            return nullptr;
+        }
+        if (variable->getType().containsOpaque()) {
+            error(loc, "null initializers can't be used on opaque values", "{}", "");
+            return nullptr;
+        }
+        variable->getWritableType().getQualifier().setNullInit();
         return nullptr;
     }
+
     arrayObjectCheck(loc, variable->getType(), "array initializer");
 
     //
@@ -6868,13 +6900,15 @@ TIntermNode* TParseContext::executeInitializer(const TSourceLoc& loc, TIntermTyp
 
     // Uniforms require a compile-time constant initializer
     if (qualifier == EvqUniform && ! initializer->getType().getQualifier().isFrontEndConstant()) {
-        error(loc, "uniform initializers must be constant", "=", "'%s'", variable->getType().getCompleteString().c_str());
+        error(loc, "uniform initializers must be constant", "=", "'%s'",
+              variable->getType().getCompleteString().c_str());
         variable->getWritableType().getQualifier().makeTemporary();
         return nullptr;
     }
     // Global consts require a constant initializer (specialization constant is okay)
     if (qualifier == EvqConst && symbolTable.atGlobalLevel() && ! initializer->getType().getQualifier().isConstant()) {
-        error(loc, "global const initializers must be constant", "=", "'%s'", variable->getType().getCompleteString().c_str());
+        error(loc, "global const initializers must be constant", "=", "'%s'",
+              variable->getType().getCompleteString().c_str());
         variable->getWritableType().getQualifier().makeTemporary();
         return nullptr;
     }
@@ -6894,7 +6928,8 @@ TIntermNode* TParseContext::executeInitializer(const TSourceLoc& loc, TIntermTyp
         // "In declarations of global variables with no storage qualifier or with a const
         // qualifier any initializer must be a constant expression."
         if (symbolTable.atGlobalLevel() && ! initializer->getType().getQualifier().isConstant()) {
-            const char* initFeature = "non-constant global initializer (needs GL_EXT_shader_non_constant_global_initializers)";
+            const char* initFeature =
+                "non-constant global initializer (needs GL_EXT_shader_non_constant_global_initializers)";
             if (isEsProfile()) {
                 if (relaxedErrors() && ! extensionTurnedOn(E_GL_EXT_shader_non_constant_global_initializers))
                     warn(loc, "not allowed in this version", initFeature, "");
@@ -6908,7 +6943,8 @@ TIntermNode* TParseContext::executeInitializer(const TSourceLoc& loc, TIntermTyp
         // Compile-time tagging of the variable with its constant value...
 
         initializer = intermediate.addConversion(EOpAssign, variable->getType(), initializer);
-        if (! initializer || ! initializer->getType().getQualifier().isConstant() || variable->getType() != initializer->getType()) {
+        if (! initializer || ! initializer->getType().getQualifier().isConstant() ||
+            variable->getType() != initializer->getType()) {
             error(loc, "non-matching or non-convertible constant type for const initializer",
                   variable->getType().getStorageQualifierString(), "");
             variable->getWritableType().getQualifier().makeTemporary();

glslang/MachineIndependent/Versions.cpp

@@ -305,6 +305,7 @@ void TParseVersions::initializeExtensionBehavior()
     extensionBehavior[E_GL_EXT_tessellation_point_size]              = EBhDisable;
     extensionBehavior[E_GL_EXT_texture_buffer]                       = EBhDisable;
     extensionBehavior[E_GL_EXT_texture_cube_map_array]               = EBhDisable;
+    extensionBehavior[E_GL_EXT_null_initializer]                     = EBhDisable;
 
     // OES matching AEP
     extensionBehavior[E_GL_OES_geometry_shader]          = EBhDisable;
@@ -408,9 +409,12 @@ void TParseVersions::getPreamble(std::string& preamble)
             "#define GL_EXT_shader_non_constant_global_initializers 1\n"
             ;
 
-            if (isEsProfile() && version >= 300) {
+            if (version >= 300) {
                 preamble += "#define GL_NV_shader_noperspective_interpolation 1\n";
             }
+            if (version >= 310) {
+                preamble += "#define GL_EXT_null_initializer 1\n";
+            }
 
     } else { // !isEsProfile()
         preamble =
@@ -538,6 +542,9 @@ void TParseVersions::getPreamble(std::string& preamble)
             if (profile == ECompatibilityProfile)
                 preamble += "#define GL_compatibility_profile 1\n";
         }
+        if (version >= 140) {
+            preamble += "#define GL_EXT_null_initializer 1\n";
+        }
 #endif // GLSLANG_WEB
     }
 

glslang/MachineIndependent/Versions.h

@@ -201,6 +201,7 @@ const char* const E_GL_EXT_blend_func_extended              = "GL_EXT_blend_func
 const char* const E_GL_EXT_shader_implicit_conversions      = "GL_EXT_shader_implicit_conversions";
 const char* const E_GL_EXT_fragment_shading_rate            = "GL_EXT_fragment_shading_rate";
 const char* const E_GL_EXT_shader_image_int64               = "GL_EXT_shader_image_int64";
+const char* const E_GL_EXT_null_initializer                 = "GL_EXT_null_initializer";
 
 // Arrays of extensions for the above viewportEXTs duplications
 

glslang/MachineIndependent/glslang.m4

@@ -3575,6 +3575,12 @@ GLSLANG_WEB_EXCLUDE_ON
         parseContext.profileRequires($1.loc, ~EEsProfile, 420, E_GL_ARB_shading_language_420pack, initFeature);
         $$ = $2;
     }
+    | LEFT_BRACE RIGHT_BRACE {
+        const char* initFeature = "empty { } initializer";
+        parseContext.profileRequires($1.loc, EEsProfile, 0, E_GL_EXT_null_initializer, initFeature);
+        parseContext.profileRequires($1.loc, ~EEsProfile, 0, E_GL_EXT_null_initializer, initFeature);
+        $$ = parseContext.intermediate.makeAggregate($1.loc);
+    }
 GLSLANG_WEB_EXCLUDE_OFF
     ;
 

glslang/MachineIndependent/glslang.y

@@ -3575,6 +3575,12 @@ initializer
         parseContext.profileRequires($1.loc, ~EEsProfile, 420, E_GL_ARB_shading_language_420pack, initFeature);
         $$ = $2;
     }
+    | LEFT_BRACE RIGHT_BRACE {
+        const char* initFeature = "empty { } initializer";
+        parseContext.profileRequires($1.loc, EEsProfile, 0, E_GL_EXT_null_initializer, initFeature);
+        parseContext.profileRequires($1.loc, ~EEsProfile, 0, E_GL_EXT_null_initializer, initFeature);
+        $$ = parseContext.intermediate.makeAggregate($1.loc);
+    }
 
     ;
 

gtests/Spv.FromFile.cpp

@@ -376,6 +376,7 @@ INSTANTIATE_TEST_SUITE_P(
         "spv.nonuniform4.frag",
         "spv.nonuniform5.frag",
         "spv.noWorkgroup.comp",
+        "spv.nullInit.comp",
         "spv.offsets.frag",
         "spv.Operations.frag",
         "spv.paramMemory.frag",