GPU: Add support for small types

This implement the design of #118961.

- Add aliases in GLSL since theses types are
  not supported.
- Add detection mechanism that prevents usage
  inside shader shared code.

Check is only done in debug build to avoid slowing down
application startup.

Pull Request: https://projects.blender.org/blender/blender/pulls/119226

source/blender/gpu/intern/gpu_shader_dependency.cc

@@ -104,6 +104,7 @@ struct GPUSource {
     if (filename.endswith(".h") || filename.endswith(".hh")) {
       enum_preprocess();
       quote_preprocess();
+      small_types_check();
     }
     else {
       if (source.find("'") != StringRef::not_found) {
@@ -236,6 +237,45 @@ struct GPUSource {
     source = processed_source.c_str();
   }
 
+  /**
+   * Assert not small types are present inside shader shared files.
+   */
+  void small_types_check()
+  {
+#ifndef NDEBUG
+    auto check_type = [&](StringRefNull type_str) {
+      int64_t cursor = -1;
+      while (true) {
+        cursor = find_keyword(source, type_str, cursor + 1);
+        if (cursor == -1) {
+          break;
+        }
+        print_error(source, cursor, "small types are forbidden in shader interfaces");
+      }
+    };
+    check_type("char ");
+    check_type("char2 ");
+    check_type("char3 ");
+    check_type("char4 ");
+    check_type("uchar ");
+    check_type("uchar2 ");
+    check_type("uchar3 ");
+    check_type("uchar4 ");
+    check_type("short ");
+    check_type("short2 ");
+    check_type("short3 ");
+    check_type("short4 ");
+    check_type("ushort ");
+    check_type("ushort2 ");
+    check_type("ushort3 ");
+    check_type("ushort4 ");
+    check_type("half ");
+    check_type("half2 ");
+    check_type("half3 ");
+    check_type("half4 ");
+#endif
+  }
+
   /**
    * Transform C,C++ enum declaration into GLSL compatible defines and constants:
    *

source/blender/gpu/shaders/opengl/glsl_shader_defines.glsl

@@ -36,6 +36,32 @@
 #define float3x4 mat3x4
 #define float4x4 mat4x4
 
+/* Small types are unavailable in GLSL (or badly supported), promote them to bigger type. */
+#define char int
+#define char2 int2
+#define char3 int3
+#define char4 int4
+#define short int
+#define short2 int2
+#define short3 int3
+#define short4 int4
+#define uchar uint
+#define uchar2 uint2
+#define uchar3 uint3
+#define uchar4 uint4
+#define ushort uint
+#define ushort2 uint2
+#define ushort3 uint3
+#define ushort4 uint4
+#define half float
+#define half2 float2
+#define half3 float3
+#define half4 float4
+
+/* Aliases for supported fixed width types. */
+#define int32_t int
+#define uint32_t uint
+
 /* Fast store variant macro. In GLSL this is the same as imageStore, but assumes no bounds
  * checking. */
 #define imageStoreFast imageStore