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[ggml-webgpu] Handle buffer overlap / buffer aliasing for concat operator#24000

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reeselevine merged 22 commits into
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Jun 8, 2026
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[ggml-webgpu] Handle buffer overlap / buffer aliasing for concat operator#24000
reeselevine merged 22 commits into
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nikhilJain17:nikhilJain17/concat-overlap

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@nikhilJain17

@nikhilJain17 nikhilJain17 commented Jun 2, 2026 •
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Overview

While testing the WebGPU backend with stable-diffusion.cpp, I encountered the following error:

Device error! Reason: 2, Message: Writable storage buffer binding aliasing found between [BindGroup "concat_f32"] 
set at bind group index 0, binding index 0, and [BindGroup "concat_f32"] set at bind group index 0, binding index 1, 
with overlapping ranges (offset: 2924288, size: 1310720) and (offset: 2924288, size: 1310720) in [Buffer "tensor_buf2"].

Since WebGPU does not allow a read bind and a write bind on the same buffer, there was a workaround to merge two overlapping src buffers into a merged_src buffer in #22456. This diff applies the same technique to the concat shader.

cc @yomaytk

Requirements

  • I have read and agree with the contributing guidelines
  • AI usage disclosure: Yes, to root cause the issue and fix a git issue.

nikhilJain17 and others added 20 commits January 30, 2026 12:15
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Merge
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Merge
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merge
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Merge with master
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Merge
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Merge
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merge with master
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merge with master
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Merge
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Merge branch 'master' of https://github.com/nikhilJain17/llama.cpp
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@nikhilJain17
Merge branch 'master' of https://github.com/nikhilJain17/llama.cpp
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@nikhilJain17
Only run webgpu CI on my fork
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@nikhilJain17
Merge branch 'master' of https://github.com/nikhilJain17/llama.cpp
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# Conflicts:
#	.github/workflows/build.yml
@nikhilJain17
Merge branch 'master' of https://github.com/nikhilJain17/llama.cpp
e92f013 
# Conflicts:
#	.github/workflows/build.yml
@nikhilJain17
Add webgpu only workflow
931d5d1
@nikhilJain17
Merge branch 'master' of https://github.com/nikhilJain17/llama.cpp
69bdd8d
@nikhilJain17
Merge branch 'master' of https://github.com/nikhilJain17/llama.cpp
bb6ed31
@nikhilJain17
fix
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@nikhilJain17
handle buffer overlap case for concat operator
aae41cf
@nikhilJain17 @claude
restore build-webgpu.yml
8cb549f 
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
@github-actions github-actions Bot added ggml changes relating to the ggml tensor library for machine learning WebGPU labels Jun 2, 2026
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nikhilJain17 marked this pull request as ready for review June 2, 2026 04:50
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nikhilJain17 requested a review from a team as a code owner June 2, 2026 04:50
@yomaytk

yomaytk commented Jun 2, 2026

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Hi @nikhilJain17, thanks for working on this, and it all looks great! LGTM

reeselevine
reeselevine reviewed Jun 3, 2026
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Comment thread ggml/src/ggml-webgpu/wgsl-shaders/concat.wgsl Outdated
@reeselevine
reeselevine requested a review from CISC June 5, 2026 17:45
CISC
CISC approved these changes Jun 5, 2026
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Comment thread ggml/src/ggml-webgpu/ggml-webgpu.cpp
shader_lib_ctx.src1 = nullptr;
shader_lib_ctx.dst = dst;
shader_lib_ctx.max_wg_size = ctx->global_ctx->capabilities.limits.maxComputeInvocationsPerWorkgroup;
shader_lib_ctx.max_wg_size = ctx->global_ctx->capabilities.limits.maxComputeInvocationsPerWorkgroup;

@CISC CISC Jun 5, 2026

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Deja-vú. :)

@reeselevine
reeselevine merged commit 1705d43 into ggml-org:master Jun 8, 2026
28 of 31 checks passed
turbo-tan pushed a commit to turbo-tan/llama.cpp-tq3 that referenced this pull request Jun 11, 2026
@nikhilJain17 @claude
@reeselevine @turbo-tan
[ggml-webgpu] Handle buffer overlap / buffer aliasing for concat oper…
911a3ef 
…ator (ggml-org#24000)

* Only run webgpu CI on my fork

* Add webgpu only workflow

* handle buffer overlap case for concat operator

* restore build-webgpu.yml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Run clang-format

* Update ggml/src/ggml-webgpu/wgsl-shaders/concat.wgsl

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Reese Levine <reeselevine1@gmail.com>
(cherry picked from commit 1705d43)
adrianhoehne pushed a commit to adrianhoehne/llama.cpp that referenced this pull request Jul 5, 2026
@nikhilJain17 @claude @reeselevine
[ggml-webgpu] Handle buffer overlap / buffer aliasing for concat oper…
035ae64 
…ator (ggml-org#24000)

* Only run webgpu CI on my fork

* Add webgpu only workflow

* handle buffer overlap case for concat operator

* restore build-webgpu.yml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Run clang-format

* Update ggml/src/ggml-webgpu/wgsl-shaders/concat.wgsl

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Reese Levine <reeselevine1@gmail.com>
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@CISC CISC CISC approved these changes
@reeselevine reeselevine reeselevine approved these changes
@yomaytk yomaytk yomaytk approved these changes

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@nikhilJain17 @yomaytk @CISC @reeselevine