Bug Report: The expected result for vulkan vertex input test with format VK_FORMAT_R8_SRGB

[Jasonjunsu]

Runing the vulkan CTS case, dEQP-VK.pipeline.monolithic.vertex_input.single_attribute.float.as_r8_srgb_rate_vertex. I got the VS as below

#version 440
layout(constant_id = 0) const int numAttributes = 16;
layout(location = 0) in float attr0;
layout(location = 0) out highp vec4 vtxColor;
out gl_PerVertex {
    vec4 gl_Position;
};

void main(void)
{
    int okCount = 0;
    if (abs(attr0 - (0.003922 * (1.0 * float(gl_VertexIndex) + 0.0))) < 0.001000)
        okCount++;

    if (okCount == 1)
    {
        if (gl_InstanceIndex == 0)
            vtxColor = vec4(1.0, 0.0, 0.0, 1.0);
        else
            vtxColor = vec4(0.0, 0.0, 1.0, 1.0);
    }
    else
    {
        vtxColor = vec4(okCount / float(1), 0.0f, 0.0f, 1.0);
    }

    if (gl_InstanceIndex == 0)
    {
        if (gl_VertexIndex == 0) gl_Position = vec4(-1.0, -1.0, 0.0, 1.0);
        else if (gl_VertexIndex == 1) gl_Position = vec4(0.0, -1.0, 0.0, 1.0);
        else if (gl_VertexIndex == 2) gl_Position = vec4(-1.0, 1.0, 0.0, 1.0);
        else if (gl_VertexIndex == 3) gl_Position = vec4(0.0, 1.0, 0.0, 1.0);
        else gl_Position = vec4(0.0);
    }
    else
    {
        if (gl_VertexIndex == 0) gl_Position = vec4(0.0, -1.0, 0.0, 1.0);
        else if (gl_VertexIndex == 1) gl_Position = vec4(1.0, -1.0, 0.0, 1.0);
        else if (gl_VertexIndex == 2) gl_Position = vec4(0.0, 1.0, 0.0, 1.0);
        else if (gl_VertexIndex == 3) gl_Position = vec4(1.0, 1.0, 0.0, 1.0);
        else gl_Position = vec4(0.0);
    }
}

But I found there is a possible issue. I think the expected vertex attribute result attr0 should be normalized and converted into linear color space.

if 0x01is the value in vertex buffer with location = 0 , and the final result of attr0 should be caculated as below:
float val_normalized = 1.0 / 255 = 0.003922
float attr0 = val_normalized / 12.92 = 0.003922 / 12.92 = 0.0003035

so the condition check statement should be fixed as below

 if (abs(attr0 - (0.003922 * (1.0 * float(gl_VertexIndex) + 0.0))) < 0.001000)

-->

float srgbToLinear(float srgbColor) {
    if (srgbColor <= 0.04045) {
        return srgbColor / 12.92;
    } else {
        return pow((srgbColor + 0.055) / 1.055, 2.4);
    }
}
 //......
 float normalized_val = 0.003922 * (1.0 * float(gl_VertexIndex) + 0.0);
 if (abs(attr0 - srgbToLinear(normalized_val)) < 0.001000)