glsl: textureGatherOffset param broken

The following compute shader from KHR-GL46.sparse_texture2_tests.SparseTexture2Lookup is broken in Mesa:

#version 450 core

#extension GL_ARB_sparse_texture2 : enable
#extension GL_ARB_sparse_texture_clamp : enable

layout (local_size_x = 1, local_size_y = 1, local_size_z = 1) in;

layout (location = 1, r8ui) writeonly uniform uimage2D uni_out;
layout (location = 2) uniform sampler2D uni_in;
layout (location = 3) uniform int widthCommitted;

void main()
{
    ivec2 point = ivec2(gl_WorkGroupID.x, gl_WorkGroupID.y);
    ivec2 texSize = ivec2(512, 512);
    ivec2 icoord = ivec2(gl_WorkGroupID.x, gl_WorkGroupID.y);
    vec2 coord = vec2(gl_WorkGroupID.x, gl_WorkGroupID.y) / vec2(texSize);
    vec4 retValue,
                  expValue,
                  epsilon;
    retValue = vec4(0);
    expValue = vec4(1, 1, 1, 1);
    epsilon = vec4(0.008);


    ivec2 offsetsArray[4];
    offsetsArray[0] = ivec2(0);
    offsetsArray[1] = ivec2(0);
    offsetsArray[2] = ivec2(0);
    offsetsArray[3] = ivec2(0);


    ivec2 corner1 = ivec2(1, 1);
    ivec2 corner2 = ivec2(texSize.x - 1, texSize.y - 1);

    int code = sparseTextureGatherOffsetsARB(uni_in,
                          coord, offsetsArray,
                          retValue, 0);
    memoryBarrier();

    imageStore(uni_out, point, uvec4(255));

    if (point.x > corner1.x && point.y > corner1.y &&
        point.x < corner2.x && point.y < corner2.y &&
        point.x < widthCommitted - 1)
    {
        if (!sparseTexelsResidentARB(code) ||
            any(greaterThan(retValue, expValue + epsilon)) ||
            any(lessThan(retValue, expValue - epsilon)))
        {
            imageStore(uni_out, point, uvec4(0));
        }
    }

    if (point.x > corner1.x && point.y > corner1.y &&
        point.x < corner2.x && point.y < corner2.y &&
        point.x >= widthCommitted + 1)
    {
        if (sparseTexelsResidentARB(code))
        {
            imageStore(uni_out, point, uvec4(0));
        }
    }
}

Log:

0:37(9): error: parameter `in offsets' must be a constant expression
0:47(31): warning: `code' used uninitialized
0:59(30): warning: `code' used uninitialized

• code is not uninitialized
• in offsets is the offsets param (offsetsArray) for sparseTextureGatherOffsetsARB, and the GLSL compiler is failing to detect that it's constant because it is an array variable with constant values assigned to it rather than a constant value. According to GLSL 4.6 (page 300): The specified values in offsets must be constant.