mesa/main: rework GL_IMAGE_PIXEL_TYPE query

This used to depend on both _mesa_get_shader_image_format() and
_mesa_uncompressed_format_to_type_and_comps() doing a specific mapping
to behave like the spec requires. But only a small subset of what the
latter function does is needed, and that function is used for other
purposes where the needs are dictated by other means.

It's going to be easier to maintain this code if we use different
implementations for these two things.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29386>

src/mesa/main/formatquery.c

@@ -1507,21 +1507,14 @@ _mesa_GetInternalformativ(GLenum target, GLenum internalformat, GLenum pname,
    }
 
    case GL_IMAGE_PIXEL_TYPE: {
-      mesa_format image_format;
       GLenum datatype;
-      GLuint comps;
 
       if (!_mesa_has_ARB_shader_image_load_store(ctx) ||
           target == GL_RENDERBUFFER)
          goto end;
 
-      image_format = _mesa_get_shader_image_format(internalformat);
-      if (image_format == MESA_FORMAT_NONE)
-         goto end;
-
-      _mesa_uncompressed_format_to_type_and_comps(image_format, &datatype,
-                                                  &comps);
-      if (!datatype)
+      datatype = _mesa_get_shader_image_pixel_type(internalformat);
+      if (datatype == GL_NONE)
          goto end;
 
       buffer[0] = datatype;

src/mesa/main/shaderimage.c

@@ -165,6 +165,77 @@ _mesa_get_shader_image_format(GLenum format)
    }
 }
 
+GLenum
+_mesa_get_shader_image_pixel_type(GLenum image_format)
+{
+   /* This is the mapping from image format to pixel type described in table
+    * 8.35 from the OpenGL 4.6 Compatibility spec.
+    */
+   switch (image_format) {
+   case GL_RGBA32F:
+   case GL_RG32F:
+   case GL_R32F:
+      return GL_FLOAT;
+
+   case GL_RGBA16F:
+   case GL_RG16F:
+   case GL_R16F:
+      return GL_HALF_FLOAT;
+
+   case GL_R11F_G11F_B10F:
+      return GL_UNSIGNED_INT_10F_11F_11F_REV;
+
+   case GL_RGBA32UI:
+   case GL_RG32UI:
+   case GL_R32UI:
+      return GL_UNSIGNED_INT;
+
+   case GL_RGBA16UI:
+   case GL_RG16UI:
+   case GL_R16UI:
+   case GL_RGBA16:
+   case GL_RG16:
+   case GL_R16:
+      return GL_UNSIGNED_SHORT;
+
+   case GL_RGB10_A2UI:
+   case GL_RGB10_A2:
+      return GL_UNSIGNED_INT_2_10_10_10_REV;
+
+   case GL_RGBA8UI:
+   case GL_RG8UI:
+   case GL_R8UI:
+   case GL_RGBA8:
+   case GL_RG8:
+   case GL_R8:
+      return GL_UNSIGNED_BYTE;
+
+   case GL_RGBA32I:
+   case GL_RG32I:
+   case GL_R32I:
+      return GL_INT;
+
+   case GL_RGBA16I:
+   case GL_RG16I:
+   case GL_R16I:
+   case GL_RGBA16_SNORM:
+   case GL_RG16_SNORM:
+   case GL_R16_SNORM:
+      return GL_SHORT;
+
+   case GL_RGBA8I:
+   case GL_RG8I:
+   case GL_R8I:
+   case GL_RGBA8_SNORM:
+   case GL_RG8_SNORM:
+   case GL_R8_SNORM:
+      return GL_BYTE;
+
+   default:
+      return GL_NONE;
+   }
+}
+
 enum image_format_class
 {
    /** Not a valid image format. */

src/mesa/main/shaderimage.h

@@ -42,6 +42,12 @@ struct gl_context;
 mesa_format
 _mesa_get_shader_image_format(GLenum format);
 
+/**
+ * Get the pixel type GL enum from the shader image format GL enum.
+ */
+GLenum
+_mesa_get_shader_image_pixel_type(GLenum image_format);
+
 /**
  * Get the GL image format class for a shader image format GL enum
  */