Describe discard as demoting to a helper invocation #3176
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wgsl/index.bs
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| ## Fragment Shaders and Helper Invocations ## {#fragment-shaders-helper-invocations} | ||
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| Invocations in the [=fragment shader stage=] are divided into 2x2 grids of neighbouring invocations. |
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Should say in what sense they are "neighbouring".
Suggest
of invocations with neighboring framebuffer positions in the X and Y dimensions.
(I filed separate issue #3177 so we can make 'position' a cross-reference)
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I rebased on top of the definitions and made this a link.
wgsl/index.bs
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| [[#texturestore|textureStore]] function calls performed by helper invocations | ||
| will have no effect on the texture. | ||
| [[#atomic-builtin-functions|Atomic built-in funtions]] performed by helper | ||
| invocations will return undefined results. |
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And atomic operations don't write.
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That's covered by the write access restriction above.
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Fixes gpuweb#921 * Change the behavior of `discard` to convert the invocation into a helper invocation * Update behavior analysis to remove the Discard behavior * Additionally remove the analysis of expressions since functions can only have the behaviors {} (an error) or {Next} * Add a section describing helper invocations in fragment shdaers
* remove discard bullet about entry point return evaluation * better introduce helper invocations in terms of rasterization * fix typos
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| This repetition can be interrupted by a [=statement/break=], [=statement/return=], or | ||
| [=statement/discard=] statement. | ||
| This repetition can be interrupted by a [=statement/break=], or | ||
| [=statement/return=] statement. |
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The repetition may be interrupted if all invocations in the quad discard and get demoted to helper?
| The compound statement [=shader-creation error|must not=] contain a [=statement/return=] at any compound statement nesting level. | ||
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| The compound statement [=shader-creation error|must not=] contain a [=statement/discard=] at any compound statement nesting level nor through function calls. | ||
| See [[#behaviors]] for a more formal description of this rule. |
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What about if all invocations discard? Is that valid or invalid?
* Describe discard as demoting to a helper invocation Fixes gpuweb#921 * Change the behavior of `discard` to convert the invocation into a helper invocation * Update behavior analysis to remove the Discard behavior * Additionally remove the analysis of expressions since functions can only have the behaviors {} (an error) or {Next} * Add a section describing helper invocations in fragment shdaers * Clarify textureStore and entry point returns don't happen for helpers * Address review feedback * remove discard bullet about entry point return evaluation * better introduce helper invocations in terms of rasterization * fix typos * Improve restriction wording * fix typo * Add link to position
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Fixes #921
discardto convert the invocation into ahelper invocation
only have the behaviors {} (an error) or {Next}