[naga wgsl-out] Represent min value i64 literals as -9223372036854775807li - 1li
#7424
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…5807li - 1li` ie the second-most negative value minus 1. The most negative value of an integer type is not directly expressible in WGSL, as it relies on applying the unary negation operator to a value which is one larger than the largest value representable by the type. To avoid this issue for i32, we negate the required value as an AbstractInt before converting to i32. AbstractInt, being 64 bits, is capable of representing the maximum i32 value + 1. However, for i64 this is not the case. Instead this patch makes us express the mimimum i64 value as the second most negative i64 value, minus 1, ie `-9223372036854775807li - 1li`, thereby avoiding the issue.
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ErichDonGubler
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Mar 25, 2025
jamienicol
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Mar 27, 2025
gfx-rs#7424 fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
jamienicol
added a commit
to LegNeato/wgpu
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Mar 27, 2025
gfx-rs#7424 fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
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jamienicol
added a commit
to LegNeato/wgpu
that referenced
this pull request
Mar 27, 2025
gfx-rs#7424 fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
jamienicol
added a commit
to LegNeato/wgpu
that referenced
this pull request
Mar 27, 2025
In gfx-rs#7424 we fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
jamienicol
added a commit
to LegNeato/wgpu
that referenced
this pull request
Mar 27, 2025
In gfx-rs#7424 we fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
LegNeato
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that referenced
this pull request
Apr 9, 2025
In gfx-rs#7424 we fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
ErichDonGubler
pushed a commit
that referenced
this pull request
Apr 9, 2025
In #7424 we fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
Vecvec
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Apr 11, 2025
In gfx-rs#7424 we fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
jimblandy
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Apr 18, 2025
In gfx-rs#7424 we fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
sharmajai
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Oct 12, 2025
…5807li - 1li` (gfx-rs#7424) ie the second-most negative value minus 1. The most negative value of an integer type is not directly expressible in WGSL, as it relies on applying the unary negation operator to a value which is one larger than the largest value representable by the type. To avoid this issue for i32, we negate the required value as an AbstractInt before converting to i32. AbstractInt, being 64 bits, is capable of representing the maximum i32 value + 1. However, for i64 this is not the case. Instead this patch makes us express the mimimum i64 value as the second most negative i64 value, minus 1, ie `-9223372036854775807li - 1li`, thereby avoiding the issue.
sharmajai
pushed a commit
to sharmajai/wgpu
that referenced
this pull request
Oct 12, 2025
In gfx-rs#7424 we fixed a bug where the representation of the minimum int64 literal generated by naga was invalid WGSL. It changed us from expressing it as `-9223372036854775808` which was invalid, to `-9223372036854775807li - 1li`. This is valid WGSL. However, as the values are concrete i64 types if the shader is parsed again by naga the expression does not get const evaluated away, leading to suboptimal code generated by the backends. This patch makes us perform the subtraction using abstract integers before casting to i64, solving this problem. Additionally the input WGSL test is updated to use the same construct.
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Connections
Fixes #7423
Description
See #7423
Testing
Added line to int64 snapshot test. WGSL output previously failed validation but now passes
Squash or Rebase?
Either
Checklist
cargo fmt.taplo format.cargo clippy --tests. If applicable, add:cargo xtask testto run tests.