Overlapping explicit binding of uniform buffer produces incorrect values

[sivansh11]

explictly setting the same binding and space for multiple uniform buffers doesnt work (gives nonsensical values)

[[vk_binding(0,0)]] uniform readonly uint64_t addresses[1000];
[[vk_binding(0,0)]] uniform readonly uint64_t addresses1[1000];

gives

addresses 0
addresses1 8000

I doubt this is intentional, do let me know if I am wrong.

on commit 5da06d4

[ArielG-NV]

edit: answered in another comment.

[csyonghe]

Aliasing binding is allowed, but the code isn’t using the right syntax to define buffers. A buffer should be declared as StructuredBuffer, but the vk_binding in the provided code is declared directly on an ordinary data field that will be placed in the default constant buffer, the vk_binding will have no meaning in this case.

you probably want:

[vk::binding(0,0)] ConstantBuffer<uint[1000]> addresses;
[vk::binding(0,0)] ConstantBuffer<uint[1000]> addresses1;

which defines two constant buffer resources that maps to a same binding. Note that global ordinary iniform data cannot have a binding.

[ArielG-NV]

Note that global ordinary uniform data cannot have a binding.

@csyonghe should this also produce a warning?

[ArielG-NV]

or should we allow automatically mapping [[vk_binding(0,0)]] to equivalent layout syntax in this senario?

(or maybe do both?)

[csyonghe]

I would say a warning for now on binding attributes declared on uniform data.

[ArielG-NV]

I was reading our user guide and it seems we don't explicitly support or don't support the behavior described in this issue, this should be changed as per discussion and issue

Binding information for Vulkan (and OpenGL) may be specified using [[vk::binding(...)]] attributes.

into

Binding information for Vulkan (and OpenGL) may be specified using [[vk::binding(...)]] attributes. It is highly recommended to use ConstantBuffer<T> instead of uniform with vk::binding.

[sivansh11]

@csyonghe ahh got you, didnt know ordinary uniforms couldnt have an explicit binding,

I tried out using ConstantBuffer, but I am getting a segfault

[[vk::binding(0, 0)]] uniform ConstantBuffer<uint64_t[1000]> addresses;
[[vk::binding(0, 0)]] uniform ConstantBuffer<uint64_t[1000]> addresses1;

[shader("compute")]
[numthreads(1, 1, 1)]
void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID, uint groupIndex: SV_GroupIndex) {
    printf("\nfrom gpu: %llu", addresses1[0]);
    printf("\nfrom gpu: %llu", addresses1[1]);
}

my usage should be correct now ?

I am using u64 to debug because those are VkDeviceAddresses.
In actuallity I want to use pointers, I was hoping that I could just have an array of void *, but that causes another set of problems in slang (issue #4674)

[ArielG-NV]

I tried out using ConstantBuffer, but I am getting a segfault

What would be the compile command used if I may ask?

[csyonghe]

Looks like it is the array directly inside a ConstantBuffer causing error. This works:

struct V {uint64_t a[1000];};

[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses;
[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses1;

[shader("compute")]
[numthreads(1, 1, 1)]
void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID, uint groupIndex: SV_GroupIndex) {
    printf("\nfrom gpu: %llu", addresses.a[0]);
    printf("\nfrom gpu: %llu", addresses1.a[1]);
}

[sivansh11]

@ArielG-NV I am using the c++ api,

DebugInformation SLANG_DEBUG_INFO_LEVEL_MAXIMAL
Optimization SLANG_OPTIMIZATION_LEVEL_NONE
GLSLForceScalarLayout 1

[sivansh11]

Looks like it is the array directly inside a ConstantBuffer causing error. This works:

struct V {uint64_t a[1000];};

[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses;
[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses1;

[shader("compute")]
[numthreads(1, 1, 1)]
void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID, uint groupIndex: SV_GroupIndex) {
    printf("\nfrom gpu: %llu", addresses.a[0]);
    printf("\nfrom gpu: %llu", addresses1.a[1]);
}

it compiles now, but I am still getting a validation error while trying to create the shader module

Validation Error: [ UNASSIGNED-Debug-Printf ] | MessageID = 0x9472fbd3 | vkCreateShaderModule():  Error during shader instrumentation in spirv-opt: line 71: ID '50' decorated with Block multiple times is not allowed.
  %V_natural = OpTypeStruct %_Array_natural_uint641000

if you are able to run it, may I know the commit you are on ?

[ArielG-NV]

@ArielG-NV I am using the c++ api,

DebugInformation SLANG_DEBUG_INFO_LEVEL_MAXIMAL Optimization SLANG_OPTIMIZATION_LEVEL_NONE GLSLForceScalarLayout 1

I will look into why

[[vk::binding(0, 0)]] uniform ConstantBuffer<uint64_t[1000]> addresses;
[[vk::binding(0, 0)]] uniform ConstantBuffer<uint64_t[1000]> addresses1;

crashes.

(issue #4704)

[ArielG-NV]

Update: #4704 has a PR out, uniform ConstantBuffer<uint64_t[1000]> addresses; should work with the PR.

it compiles now, but I am still getting a validation error while trying to create the shader module

I will now checkout this issue.

[ArielG-NV]

@sivansh11 I recommend updating your Vulkan SDK to the latest one. I seem to have no trouble compiling the suggested code with Vulkan SDK version 1.3.283.0

struct V {uint64_t a[1000];};

[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses;
[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses1;

[shader("compute")]
[numthreads(1, 1, 1)]
void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID, uint groupIndex: SV_GroupIndex) {
    printf("\nfrom gpu: %llu", addresses.a[0]);
    printf("\nfrom gpu: %llu", addresses1.a[1]);
}

[sivansh11]

@sivansh11 I recommend updating your Vulkan SDK to the latest one. I seem to have no trouble compiling the suggested code with Vulkan SDK version 1.3.283.0

struct V {uint64_t a[1000];};

[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses;
[[vk::binding(0, 0)]] uniform ConstantBuffer<V> addresses1;

[shader("compute")]
[numthreads(1, 1, 1)]
void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID, uint groupIndex: SV_GroupIndex) {
    printf("\nfrom gpu: %llu", addresses.a[0]);
    printf("\nfrom gpu: %llu", addresses1.a[1]);
}

Yes, I am on 1.3.283.0
again this is the error that I am getting while trying to run the suggested code.

Validation Error: [ UNASSIGNED-Debug-Printf ] | MessageID = 0x9472fbd3 | vkCreateShaderModule():  Error during shader instrumentation in spirv-opt: line 71: ID '50' decorated with Block multiple times is not allowed.
  %V_natural = OpTypeStruct %_Array_natural_uint641000

[ArielG-NV]

Try updating Slang to 2024.1.30

It looks like the Slang version being used is affected by a spirv-opt change which was solved by Slang in a later revision.

If this does-not fix your issue, please add a comment here so I can look into the problem further.

(note: issue was closed due to solving the original problem)