error when creating a const vector with specialization constants

[DadSchoorse]

My shader looks like that:

#version 450

layout(constant_id = 0) const float _3 = 0.1500000059604644775390625;
layout(constant_id = 1) const float _4 = 1.0;
layout(constant_id = 2) const float _5 = 1.0;
layout(constant_id = 3) const float _6 = 1.0;
const vec3 _8 = vec3(_4, _5, _6);

layout(set = 1, binding = 0) uniform sampler2D _11;
layout(set = 1, binding = 1) uniform sampler2D _15;

layout(location = 0) in vec2 _172;
layout(location = 0) out vec3 _176;

vec3 _83(vec4 _85, vec2 _86)
{
    vec3 _92 = texture(_11, _86).xyz;
    vec3 _98 = vec3(0.21265600621700286865234375, 0.715157985687255859375, 0.072186000645160675048828125);
    float _102 = dot(_98, _92);
    float _114 = max(_92.x, max(_92.y, _92.z));
    float _126 = min(_92.x, min(_92.y, _92.z));
    float _130 = _114 - _126;
    vec3 _133 = _8 * vec3(_3);
    _92 = mix(vec3(_102), _92, vec3(1.0) + (_133 * (vec3(1.0) - (sign(_133) * vec3(_130)))));
    return _92;
}

void main()
{
    vec4 _167 = gl_FragCoord;
    vec2 _171 = _172;
    _176 = _83(_167, _171);
}

If I try to compile that to Vulkan spir-v, the following error occurs:

ERROR: vibrance.frag.glsl:7: '=' : global const initializers must be constant ' const highp 3-component vector of float'

This usage should be valid and is even mentioned in the spec:
https://github.com/KhronosGroup/GLSL/blob/6c0a07d45d45c42e6fbe441e5199fe8497d085d7/extensions/khr/GL_KHR_vulkan_glsl.txt#L181
I have tried Version 7.13.3381 and latest master.

[DadSchoorse]

a simpler example:

#version 450

layout(constant_id = 1) const float _4 = 1.0;
const vec4 _8 = vec4(_4, _4,_4,_4);

layout(location = 0) out vec4 fragColor;

void main()
{
    fragColor = _8;
}

Expected output:

; SPIR-V
; Version: 1.0
; Generator: Khronos SPIR-V Tools Assembler; 0
; Bound: 12
; Schema: 0
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %main "main" %fragColor
               OpExecutionMode %main OriginUpperLeft
               OpSource GLSL 450
               OpName %main "main"
               OpName %fragColor "fragColor"
               OpDecorate %4 SpecId 1
               OpDecorate %fragColor Location 0
       %void = OpTypeVoid
          %6 = OpTypeFunction %void
      %float = OpTypeFloat 32
    %v4float = OpTypeVector %float 4
%_ptr_Output_v4float = OpTypePointer Output %v4float
  %fragColor = OpVariable %_ptr_Output_v4float Output
          %4 = OpSpecConstant %float 1
         %10 = OpSpecConstantComposite %v4float %4 %4 %4 %4
       %main = OpFunction %void None %6
         %11 = OpLabel
               OpStore %fragColor %10
               OpReturn
               OpFunctionEnd

That spirv works, it gets validated and changing the spec constant works, too.

[godlikepanos]

I'm also hitting this issue. If _8 is ivec or uvec it compiles just fine but it failes with plain vec types.

[haasn]

I'm also hitting this bug. Working around it using #define foo vec4(_1, _2, _3, _4) instead of const vec4 foo = vec4(_1, _2, _3, _4);, but it's annoying and I shouldn't have to do this.

Also, I think this is a bug, not missing functionality, and should be reclassified as such.

[greg-lunarg]

glslang has commented code and a commented test which holds to the policy that constant float vectors containing specialization constants are not allowed, although I can find no such policy in the Vulkan, SPIR-V or GLSL specs. The aforementioned test's file name seems to imply that the policy comes from Vulkan.

I will check with the SPIR-V WG to see if they know more about this policy. Once I have a go-ahead from them I should be posting a fix shortly after.

[greg-lunarg]

According to the SPIR-V WG, the construct const vec4 foo = vec4(_1, _2, _3, _4); is legal in SPIR-V, GLSL and Vulkan. It is only generating an error because support has not yet been implemented in glslang.

I will add support shortly.