spirv: Support initializers on uniforms

If a uniform has an initializer it will now be given as the optional
initializer operand to the OpVariable instruction.

Fixes: KhronosGroup#1259

Signed-off-by: Neil Roberts <nroberts@igalia.com> (the code)
Signed-off-by: Alejandro Piñeiro <apinheiro@igalia.com> (the tests)
Signed-off-by: Arcady Goldmints-Orlov <agoldmints@igalia.com>

SPIRV/GlslangToSpv.cpp

@@ -3524,7 +3524,18 @@ spv::Id TGlslangToSpvTraverser::createSpvVariable(const glslang::TIntermSymbol*
     if (glslang::IsAnonymous(name))
         name = "";
 
-    return builder.createVariable(storageClass, spvType, name);
+    spv::Id initializer = spv::NoResult;
+
+    if (node->getType().getQualifier().storage == glslang::EvqUniform &&
+        !node->getConstArray().empty()) {
+            int nextConst = 0;
+            initializer = createSpvConstantFromConstUnionArray(node->getType(),
+                                                               node->getConstArray(),
+                                                               nextConst,
+                                                               false /* specConst */);
+    }
+
+    return builder.createVariable(storageClass, spvType, name, initializer);
 }
 
 // Return type Id of the sampled type.

Test/baseResults/spv.uniformInitializer.frag.out

@@ -0,0 +1,33 @@
+spv.uniformInitializer.frag
+// Module Version 10000
+// Generated by (magic number): 80008
+// Id's are bound by 16
+
+                              Capability Shader
+               1:             ExtInstImport  "GLSL.std.450"
+                              MemoryModel Logical GLSL450
+                              EntryPoint Fragment 4  "main" 9
+                              ExecutionMode 4 OriginLowerLeft
+                              Source GLSL 450
+                              Name 4  "main"
+                              Name 9  "color"
+                              Name 14  "in_color"
+                              Decorate 9(color) Location 0
+                              Decorate 14(in_color) Location 0
+               2:             TypeVoid
+               3:             TypeFunction 2
+               6:             TypeFloat 32
+               7:             TypeVector 6(float) 4
+               8:             TypePointer Output 7(fvec4)
+        9(color):      8(ptr) Variable Output
+              10:    6(float) Constant 0
+              11:    6(float) Constant 1065353216
+              12:    7(fvec4) ConstantComposite 10 11 10 11
+              13:             TypePointer UniformConstant 7(fvec4)
+    14(in_color):     13(ptr) Variable UniformConstant 12
+         4(main):           2 Function None 3
+               5:             Label
+              15:    7(fvec4) Load 14(in_color)
+                              Store 9(color) 15
+                              Return
+                              FunctionEnd

Test/spv.uniformInitializer.frag

@@ -0,0 +1,10 @@
+#version 450
+
+layout (location = 0) out vec4 color;
+
+layout (location = 0) uniform vec4 in_color = vec4(0.0, 1.0, 0.0, 1.0);
+
+void main()
+{
+	color = in_color;
+}

Test/spv.uniformInitializerSpecConstant.frag

@@ -0,0 +1,14 @@
+#version 450
+
+layout (location = 0) out vec4 color;
+
+layout (constant_id = 1) const float opacity = 0.5;
+
+layout (location = 0) uniform vec3 in_color = vec3(1.0, 0.5, 0);
+
+layout (location = 4) uniform float foo = opacity;
+
+void main()
+{
+	color = vec4(in_color, foo);
+}

Test/spv.uniformInitializerStruct.frag

@@ -0,0 +1,19 @@
+#version 450
+
+layout (location = 0) out vec4 color;
+
+layout (location = 0) uniform struct {
+        float r;
+        float g;
+        float b;
+} parts[2] = { { 1.0, 1.0, 1.0}, { 0.0, 1.0, 0.0 } };
+
+void main() {
+  color = vec4(0.0, 0.0, 0.0, 1.0);
+
+  for (int i = 0; i < 2; i++) {
+    color.r += parts[i].r;
+    color.g += parts[i].g;
+    color.b += parts[i].b;
+  }
+}

gtests/Spv.FromFile.cpp

@@ -600,6 +600,9 @@ INSTANTIATE_TEST_CASE_P(
         "spv.specConst.vert",
         "spv.specTexture.frag",
         "spv.OVR_multiview.vert",
+        "spv.uniformInitializer.frag",
+        "spv.uniformInitializerSpecConstant.frag",
+        "spv.uniformInitializerStruct.frag",
         "spv.xfbOffsetOnBlockMembersAssignment.vert",
         "spv.xfbOffsetOnStructMembersAssignment.vert",
         "spv.xfbOverlapOffsetCheckWithBlockAndMember.vert",