[naga spv-out] Indexing arrays by value causes unnecessary copies #6358
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area: naga back-end
Outputs of naga shader conversion
area: performance
How fast things go
lang: SPIR-V
Vulkan's Shading Language
naga
Shader Translator
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jimblandy
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area: performance
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More exact link to comment: #6188 (comment) |
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jimblandy
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Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. Permit dynamic indexing of matrices in validation. Handle matrices and arrays consistently; remove special cases for arrays. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessIndex` for the entire thing. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Alternative to gfx-rs#6362.
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jimblandy
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Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. Permit dynamic indexing of matrices in validation. Handle matrices and arrays consistently; remove special cases for arrays. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessIndex` for the entire thing. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessIndex` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessIndex` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Fixes gfx-rs#4337. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Fixes gfx-rs#4337. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Fixes gfx-rs#4337. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 10, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Fixes gfx-rs#4337. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 11, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Fixes gfx-rs#4337. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 11, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Fixes gfx-rs#4337. Alternative to gfx-rs#6362.
jimblandy
added a commit
to jimblandy/wgpu
that referenced
this issue
Oct 11, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes gfx-rs#6358. Fixes gfx-rs#4337. Alternative to gfx-rs#6362.
jimblandy
added a commit
that referenced
this issue
Oct 11, 2024
Improve handling of `Access` expressions whose base is an array or matrix (not a pointer to such), and whose index is not known at compile time. SPIR-V does not have instructions that can do this directly, so spill such values to temporary variables, and perform the accesses using `OpAccessChain` instructions applied to the temporaries. When performing chains of accesses like `a[i].x[j]`, do not reify intermediate values; generate a single `OpAccessChain` for the entire thing. Remove special cases for arrays; the same code now handles arrays and matrices. Update validation to permit dynamic indexing of matrices. For details, see the comments on the new tracking structures in `naga::back::spv::Function`. Add snapshot test `index-by-value.wgsl`. Fixes #6358. Fixes #4337. Alternative to #6362.
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Given code like this:
the changes in #6188 will copy each intermediate indexing result into a separate variable. It would be much nicer to simply spill the value into a variable the moment we know it will be indexed dynamically, and then always use it from there.
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