wined3d: Implement the "precise" flag in the GLSL shader backend.

dlls/wined3d/glsl_shader.c

@@ -2540,6 +2540,10 @@ static void shader_generate_glsl_declarations(const struct wined3d_context_gl *c
     /* Temporary variables for matrix operations */
     shader_addline(buffer, "vec4 tmp0;\n");
     shader_addline(buffer, "vec4 tmp1;\n");
+    if (gl_info->supported[ARB_GPU_SHADER5])
+        shader_addline(buffer, "precise vec4 tmp_precise;\n");
+    else
+        shader_addline(buffer, "/* precise */ vec4 tmp_precise;\n");
 
     if (!shader->load_local_constsF)
     {
@@ -3273,6 +3277,9 @@ static DWORD shader_glsl_append_dst_ext(struct wined3d_string_buffer *buffer,
 
     if ((mask = shader_glsl_add_dst_param(ins, dst, &glsl_dst)))
     {
+        if (ins->flags & WINED3DSI_PRECISE_XYZW)
+            sprintf(glsl_dst.reg_name, "tmp_precise");
+
         switch (data_type)
         {
             case WINED3D_DATA_FLOAT:
@@ -3316,6 +3323,13 @@ static void shader_glsl_add_instruction_modifiers(const struct wined3d_shader_in
 
     if (!ins->dst_count) return;
 
+    if (ins->flags & WINED3DSI_PRECISE_XYZW)
+    {
+        shader_glsl_add_dst_param(ins, &ins->dst[0], &dst_param);
+        shader_addline(ins->ctx->buffer, "%s%s = tmp_precise%s;\n",
+                dst_param.reg_name, dst_param.mask_str, dst_param.mask_str);
+    }
+
     modifiers = ins->dst[0].modifiers;
     if (!modifiers) return;