Debug printf in shaders by exrook · Pull Request #4297 · gfx-rs/wgpu

exrook · 2023-10-25T19:10:06Z

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Run cargo clippy --target wasm32-unknown-unknown if applicable.
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Connections
Migrated from gfx-rs/naga#2563

Description
Exposes the vulkan validation layers shader printf feature to wgsl shaders through a new debugPrintf builtin function.

example:

@compute @workgroup_size(8,1,1)
fn main(@builtin(local_invocation_index) idx: u32) {
    debugPrintf("Hello from %d", idx);
}

output with validation layers enabled and configured properly:

UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 0! 
    Objects: 0
UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 1! 
    Objects: 0
UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 2! 
    Objects: 0
UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 3! 
    Objects: 0
UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 4! 
    Objects: 0
UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 5! 
    Objects: 0
UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 6! 
    Objects: 0
UNASSIGNED-DEBUG-PRINTF(INFO / SPEC): msgNum: -1841738615 - Validation Information: [ UNASSIGNED-DEBUG-PRINTF ] | MessageID = 0x92394c89 | Hello from thread 7! 
    Objects: 0

This feature is also supported on HLSL/DirectX though only when using FXC. DXC does not fully support printf, see microsoft/hlsl-specs#245.

Additionally supports converting SPIR-V shaders containing NonSemantic.DebugPrintf to wgsl, glsl, hlsl.

Testing
TBD

exrook · 2023-11-01T12:44:13Z

Looking into how the validation layers implement this, there's no reason we couldn't universally support a feature like this in a similar way with a pass on the naga IR + transparently adding a bind group to shader dispatches.

That being said I think this basic validation layer based impl would still be nice to have immediately for users on vulkan platforms.

kvark · 2023-11-09T05:22:33Z

I believe the minimal functionality in WGSL you'd need in order to support this in user space is just a string type. As soon as you have a string literal to work with, you can have WGSL preprocessor recognizing a construct and writing the format string as well as arguments into some debug buffer.

exrook · 2023-11-09T23:33:07Z

I believe the minimal functionality in WGSL you'd need in order to support this in user space is just a string type. As soon as you have a string literal to work with, you can have WGSL preprocessor recognizing a construct and writing the format string as well as arguments into some debug buffer.

The intent behind this PR was to make debugging shaders easier for wgpu users, with this PR if I want to inspect a value all I have to do is enable the validation layers and wgpu feature, and add a single line to my shader source.

Even without string support in the language a user can already implement printf-like behavior in their project, as done here for example, but I think it's a much better experience if we can provide built in debugging utilities, so I can debug my shaders without having to make any changes to my project.

cwfitzgerald

Looking good from wgpu side.

Please re-request a review from me once the changes are addressed to make sure I see it!

wgpu-hal/src/vulkan/instance.rs

wgpu-types/src/lib.rs

wgpu-hal/src/dx12/device.rs

cwfitzgerald

Approving the wgpu side!

LegNeato · 2023-12-19T02:01:11Z

Is there anything left to do here besides rebase?

cwfitzgerald · 2023-12-19T05:42:17Z

Needs a review from the Naga team, will poke them in our next meeting, but holidays are approaching, so it may be a little bit.

naga/src/front/spv/ext_inst.rs

naga/tests/out/hlsl/debug-printf-s.hlsl

jimblandy · 2023-12-21T05:46:49Z

I took the liberty of rebasing the branch on trunk, replacing the merge commit. I hope that's all right.

jimblandy · 2023-12-22T05:31:12Z

My rebase seems to have broken something. I'm looking into it.

cwfitzgerald · 2024-01-12T04:50:10Z

@exrook friendly poke :)

DXC doesn't support printf when targeting dxil, disable the test to allow CI to pass.

…tf statements

MiniaczQ · 2024-04-17T19:12:07Z

Is this ready for re-review?

cwfitzgerald

Small nits, just waiting on naga review.

cwfitzgerald · 2024-05-09T03:12:48Z

wgpu-types/src/lib.rs

+        /// Enables support for debugPrintf in WGSL shaders.
+        ///
+        /// Supported Platforms:
+        /// - DX11 (fxc only)


Suggested change

/// - DX11 (fxc only)

cwfitzgerald · 2024-05-09T03:13:24Z

wgpu-types/src/lib.rs

+        /// - DX11 (fxc only)
+        /// - DX12 (fxc only)
+        /// - Vulkan
+        /// - OpenGL


We don't support it on GL, so we should label this as an "unimplemented platform, if it is implementable

jimblandy · 2024-12-18T16:37:54Z

@exrook I'm very sorry - this PR fell through the cracks, and we didn't get around to reviewing it. The wgpu maintainers decided to review our outstanding PRs each week, and in our meeting today, everyone agreed we would like to take this PR, as it seems like something that Vulkan users use pretty frequently.

Would you be able to rebase this PR against the current trunk?

BLaZeKiLL · 2025-01-04T05:39:06Z

Looking forward to this getting merged

jimblandy · 2025-01-08T16:16:43Z

Apologies - this should have gotten prompt attention from us. But at this point the PR is two years old, and we haven't heard back from the author, so we're going to close the PR. If someone is interested in creating a fresh PR for the same feature, that'd be great.

Anutrix · 2025-05-03T14:38:37Z

Did anyone make a fresh PR salvaging this or is there still no way to log wgsl?

exrook force-pushed the debug_printf branch from 2deb7e0 to 55775ab Compare October 25, 2023 20:56

exrook mentioned this pull request Oct 25, 2023

Add debugPrintf to wgsl gfx-rs/naga#2563

Closed

exrook force-pushed the debug_printf branch from 55775ab to d675cc5 Compare November 1, 2023 12:25

exrook force-pushed the debug_printf branch 4 times, most recently from 92fc6a5 to dae4b17 Compare November 2, 2023 12:28

exrook marked this pull request as ready for review November 2, 2023 23:12

exrook requested a review from a team November 2, 2023 23:12

exrook requested a review from a team as a code owner November 2, 2023 23:12

exrook force-pushed the debug_printf branch 2 times, most recently from b6841ff to b4c2a18 Compare November 6, 2023 13:32

sholloway mentioned this pull request Nov 13, 2023

Encapsulate WebGPU - 2D sholloway/lynn-engine#96

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cwfitzgerald requested changes Nov 15, 2023

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wgpu-hal/src/vulkan/instance.rs Outdated Show resolved Hide resolved

wgpu-types/src/lib.rs Outdated Show resolved Hide resolved

wgpu-hal/src/dx12/device.rs Outdated Show resolved Hide resolved

exrook requested a review from cwfitzgerald November 16, 2023 03:32

cwfitzgerald approved these changes Nov 16, 2023

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jimblandy requested changes Dec 21, 2023

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naga/src/front/spv/ext_inst.rs Outdated Show resolved Hide resolved

naga/tests/out/hlsl/debug-printf-s.hlsl Outdated Show resolved Hide resolved

jimblandy force-pushed the debug_printf branch from fc5647c to a492318 Compare December 21, 2023 05:46

exrook force-pushed the debug_printf branch 3 times, most recently from 92bca6b to a970533 Compare December 30, 2023 16:18

cwfitzgerald requested a review from jimblandy January 8, 2024 18:12

exrook added 12 commits January 25, 2024 10:05

debug_printf: hlsl-out

396067d

debug_printf: simple validation of debugPrintf arguments

9737edc

debug_printf: add tests

d33bbdb

debug_printf: Disable hlsl-out test

a841cd4

DXC doesn't support printf when targeting dxil, disable the test to allow CI to pass.

debug_printf: Add DEBUG_PRINTF capability

ba63f1f

debug_printf: Add DEBUG_PRINTF wgpu feature

39fd577

debug_printf: Add gpu test

f1ee02d

debug_printf: Add writer flags to conditionally emit/ignore debugPrin…

a05b30a

…tf statements

debug_printf: Enable debug_printf validation feature

65d1b50

debug_printf: fix feature logic for DX12

11df7f3

debug_printf: Flatten validation layer extension logic

9ee1553

debug_printf: refactor debug_printf ext_inst handling

b010834

exrook force-pushed the debug_printf branch 3 times, most recently from 9a36c03 to d7b3be9 Compare January 25, 2024 15:30

debug_printf: Skip naga tests on DXC

3a78dca

exrook force-pushed the debug_printf branch from d7b3be9 to 3a78dca Compare January 25, 2024 15:40

ErichDonGubler mentioned this pull request Jan 26, 2024

Enable GPU-based validation for Vulkan #5046

Merged

6 tasks

Wumpf requested a review from cwfitzgerald May 4, 2024 20:13

cwfitzgerald requested changes May 9, 2024

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cwfitzgerald requested a review from a team May 9, 2024 03:13

cwfitzgerald assigned jimblandy Jan 8, 2025

jimblandy closed this Jan 8, 2025

Anutrix mentioned this pull request May 3, 2025

Way to log/debug printf in WGSL #7662

Open

stefnotch mentioned this pull request Oct 26, 2025

adding debug_printf like in vulkan wgsl-tooling-wg/wesl-spec#157

Open

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exrook commented Oct 25, 2023

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