Alter the handling of spec consts in non-Vulkan GLSL

Previously, when generating non-Vulkan GLSL, each use of a spec constant
would be subsituted for its default value and the declaration of the constant
itself would be omitted completely.

This change slightly alters this behavior. The uses of the constant are kept,
as well as the declaration, although the latter is stripped of the layout
qualifier. The declaration is also prepended with the following code:

    #ifndef <constant name>_value
    #define <constant name> <default constant value>
    #endif

and the constant itself now looks like

    const <constant type> <constant name> = <constant name>_value;

The rationale for this change is that it gives the user a way to provide
custom values for specialization constants even when the target does not
support them.

1 files changed, 7 insertions, 1 deletions

diff --git a/reference/opt/shaders/comp/composite-array-initialization.comp b/reference/opt/shaders/comp/composite-array-initialization.comp
index a47b64f1..6f5ea3a7 100644
--- a/reference/opt/shaders/comp/composite-array-initialization.comp
+++ b/reference/opt/shaders/comp/composite-array-initialization.comp
@@ -1,6 +1,12 @@
 #version 310 es
 layout(local_size_x = 2, local_size_y = 1, local_size_z = 1) in;
 
+#ifndef SPIRV_CROSS_CONSTANT_ID_0
+#define SPIRV_CROSS_CONSTANT_ID_0 4.0
+#endif
+const float X = SPIRV_CROSS_CONSTANT_ID_0;
+
+
 struct Data
 {
     float a;
@@ -15,7 +21,7 @@ layout(binding = 0, std430) buffer SSBO
 void main()
 {
     Data data[2] = Data[](Data(1.0, 2.0), Data(3.0, 4.0));
-    Data data2[2] = Data[](Data(4.0, 2.0), Data(3.0, 5.0));
+    Data data2[2] = Data[](Data(X, 2.0), Data(3.0, 5.0));
     _53.outdata[gl_WorkGroupID.x].a = data[gl_LocalInvocationID.x].a + data2[gl_LocalInvocationID.x].a;
     _53.outdata[gl_WorkGroupID.x].b = data[gl_LocalInvocationID.x].b + data2[gl_LocalInvocationID.x].b;
 }