Results for spec@arb_gpu_shader5@texturegatheroffset@vs-rgb-0-uint-2d

Failed to compile vertex shader: ERROR: 0:13: Argument 3 to function 'textureGatherOffset' must be a constant expression

source:
#version 150
#extension GL_ARB_explicit_attrib_location: require
#extension GL_ARB_texture_gather: require
#extension GL_ARB_gpu_shader5: require

layout(location=0) in vec4 pos;
uniform usampler2D s;
uniform ivec2 o1,o2;
out vec4 c;

void main() {
	gl_Position = pos;
	c = vec4(1.0/255.0) * textureGatherOffset(s, 0.5 * pos.xy + vec2(0.5)  , o1+o2 , 0);
}

PIGLIT_SOURCE_DIR="/Users/vlee/workspace/piglit" PIGLIT_PLATFORM="mixed_glx_egl"