Change ref_from_bytes() to inline(always).#3137
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When building my firmware for rv32imc with lto=fat, changing codegen-units from 16 to 1 influences the compiler heuristics enough to *not* inline this function, causing code bloat and unnecessary panic logic.
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hmm, those benchmark changes don't look good :( |
jswrenn
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Mar 19, 2026
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The benchmark results are fine. :-) There's only a six instructions overhead on the dynamic padding case, and a hypothetical cycle improvement in the dynamic size case. Since dynamically padded types are unusual, not too much weight should be put in optimizing them relative to unpadded dynamically sized types.
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Enables customers to tune inlining aggressiveness of many of zerocopy's public functions. At higher `codegen-units`, the Rust compiler may fail to inline invocations of conversion functions. Applying the `#[inline(always)]` attribute (as in #3137) forces inlining, but that might not be desirable for all monomorphizations or invocations. Dynamically padded types, for instance, require much more complex codegen than statically sized for unpadded dynamically sized types. While reducing `codegen-units` for a build can improve codegen, it carries a large penalty in build times. The `--cfg zerocopy_inline_always` flag provides a narrowly-scoped lever for achieving some of the benefits of `codegen-units=1` without the broad build time penalties. gherrit-pr-id: G750518420a745aec19276f7a24bcd0f66584bb2c
jswrenn
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Mar 19, 2026
Enables customers to tune inlining aggressiveness of many of zerocopy's public functions. At higher `codegen-units`, the Rust compiler may fail to inline invocations of conversion functions. Applying the `#[inline(always)]` attribute (as in #3137) forces inlining, but that might not be desirable for all monomorphizations or invocations. Dynamically padded types, for instance, require much more complex codegen than statically sized for unpadded dynamically sized types. While reducing `codegen-units` for a build can improve codegen, it carries a large penalty in build times. The `--cfg zerocopy_inline_always` flag provides a narrowly-scoped lever for achieving some of the benefits of `codegen-units=1` without the broad build time penalties. gherrit-pr-id: G750518420a745aec19276f7a24bcd0f66584bb2c
jswrenn
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Mar 19, 2026
Enables customers to tune inlining aggressiveness of many of zerocopy's public functions. At higher `codegen-units`, the Rust compiler may fail to inline invocations of conversion functions. Applying the `#[inline(always)]` attribute (as in #3137) forces inlining, but that might not be desirable for all monomorphizations or invocations. Dynamically padded types, for instance, require much more complex codegen than statically sized for unpadded dynamically sized types. While reducing `codegen-units` for a build can improve codegen, it carries a large penalty in build times. The `--cfg zerocopy_inline_always` flag provides a narrowly-scoped lever for achieving some of the benefits of `codegen-units=1` without the broad build time penalties. gherrit-pr-id: G750518420a745aec19276f7a24bcd0f66584bb2c
jswrenn
added a commit
that referenced
this pull request
Mar 20, 2026
Enables customers to tune inlining aggressiveness of many of zerocopy's public functions. At higher `codegen-units`, the Rust compiler may fail to inline invocations of conversion functions. Applying the `#[inline(always)]` attribute (as in #3137) forces inlining, but that might not be desirable for all monomorphizations or invocations. Dynamically padded types, for instance, require much more complex codegen than statically sized for unpadded dynamically sized types. While reducing `codegen-units` for a build can improve codegen, it carries a large penalty in build times. The `--cfg zerocopy_inline_always` flag provides a narrowly-scoped lever for achieving some of the benefits of `codegen-units=1` without the broad build time penalties. gherrit-pr-id: G750518420a745aec19276f7a24bcd0f66584bb2c
jswrenn
added a commit
that referenced
this pull request
Mar 20, 2026
Enables customers to tune inlining aggressiveness of many of zerocopy's public functions. At higher `codegen-units`, the Rust compiler may fail to inline invocations of conversion functions. Applying the `#[inline(always)]` attribute (as in #3137) forces inlining, but that might not be desirable for all monomorphizations or invocations. Dynamically padded types, for instance, require much more complex codegen than statically sized for unpadded dynamically sized types. While reducing `codegen-units` for a build can improve codegen, it carries a large penalty in build times. The `--cfg zerocopy_inline_always` flag provides a narrowly-scoped lever for achieving some of the benefits of `codegen-units=1` without the broad build time penalties. gherrit-pr-id: G750518420a745aec19276f7a24bcd0f66584bb2c
jswrenn
added a commit
that referenced
this pull request
Mar 20, 2026
Enables customers to tune inlining aggressiveness of many of zerocopy's public functions. At higher `codegen-units`, the Rust compiler may fail to inline invocations of conversion functions. Applying the `#[inline(always)]` attribute (as in #3137) forces inlining, but that might not be desirable for all monomorphizations or invocations. Dynamically padded types, for instance, require much more complex codegen than statically sized for unpadded dynamically sized types. While reducing `codegen-units` for a build can improve codegen, it carries a large penalty in build times. The `--cfg zerocopy_inline_always` flag provides a narrowly-scoped lever for achieving some of the benefits of `codegen-units=1` without the broad build time penalties. gherrit-pr-id: G750518420a745aec19276f7a24bcd0f66584bb2c
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Enables customers to tune inlining aggressiveness of many of zerocopy's public functions. At higher `codegen-units`, the Rust compiler may fail to inline invocations of conversion functions. Applying the `#[inline(always)]` attribute (as in #3137) forces inlining, but that might not be desirable for all monomorphizations or invocations. Dynamically padded types, for instance, require much more complex codegen than statically sized for unpadded dynamically sized types. While reducing `codegen-units` for a build can improve codegen, it carries a large penalty in build times. The `--cfg zerocopy_inline_always` flag provides a narrowly-scoped lever for achieving some of the benefits of `codegen-units=1` without the broad build time penalties. gherrit-pr-id: G750518420a745aec19276f7a24bcd0f66584bb2c
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When building my firmware for rv32imc with lto=fat, changing codegen-units from 16 to 1 influences the compiler heuristics enough to not inline this function, causing code bloat and unnecessary panic logic.