[Mesa-stable] [PATCH] glsl: Fix condition to generate shader link error

[Anuj Phogat]

GL_ARB_ES2_compatibility don't say anything about shader linking
when one of the shaders (vertex or fragment shader) is absent.
So, the extention shouldn't change the behavior specified in
GLSL specification.

Tested the behavior on proprietary linux drivers of NVIDIA and AMD.
Both of them allow linking a version 100 shader program in OpenGL
context, when one of the shaders is absent.

Makes following Khronos CTS tests to pass:
successfulcompilevert_linkprogram.test
successfulcompilefrag_linkprogram.test

Cc: mesa-stable at lists.freedesktop.org
Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
---
 src/glsl/linker.cpp | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index a6133ea..f84d364 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -2382,11 +2382,9 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       goto done;
 
    /* OpenGL ES requires that a vertex shader and a fragment shader both be
-    * present in a linked program.  By checking prog->IsES, we also
-    * catch the GL_ARB_ES2_compatibility case.
+    * present in a linked program.
     */
-   if (!prog->InternalSeparateShader &&
-       (ctx->API == API_OPENGLES2 || prog->IsES)) {
+   if (!prog->InternalSeparateShader && ctx->API == API_OPENGLES2) {
       if (prog->_LinkedShaders[MESA_SHADER_VERTEX] == NULL) {
 	 linker_error(prog, "program lacks a vertex shader\n");
       } else if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] == NULL) {
-- 
1.8.3.1