pulley: Allow disabling SIMD in the interpreter at compile-time #10727
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I gathered some numbers in google/wasefire#458 (comment) and for that particular embedding this is a 10% reduction in text size (44k) when compiled with |
pchickey
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This commit adds a new feature to Pulley which is used to reduce the compiled code size of the interpreter itself by disabling SIMD opcode interpretation at compile-time. The goal here is to be low-impact on Pulley itself to avoid needing `#[cfg]` all over the place and to additionally avoid the need to redesign Pulley's opcode macro for use in various parts of Wasmtime. Methods are annotated with a custom macro in the interpreter which registers a `#[cfg]` that either does the listed implementation or switches to an implementation that emits a trap if executed. This means that it's safe to execute mismatched code where SIMD was enabled at compile time but disabled at runtime, it just means the semantics may be a bit surprising to debug. Note that this SIMD is still enabled by default, and an explicit `--cfg` via `RUSTFLAGS` is required to compile-out the SIMD support. Cargo features aren't a great fit for this sort of feature so an explicit flag is used.
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This commit adds a new feature to Pulley which is used to reduce the compiled code size of the interpreter itself by disabling SIMD opcode interpretation at compile-time. The goal here is to be low-impact on Pulley itself to avoid needing
#[cfg]all over the place and to additionally avoid the need to redesign Pulley's opcode macro for use in various parts of Wasmtime.Methods are annotated with a custom macro in the interpreter which registers a
#[cfg]that either does the listed implementation or switches to an implementation that emits a trap if executed. This means that it's safe to execute mismatched code where SIMD was enabled at compile time but disabled at runtime, it just means the semantics may be a bit surprising to debug.Note that this SIMD is still enabled by default, and an explicit
--cfgviaRUSTFLAGSis required to compile-out the SIMD support. Cargo features aren't a great fit for this sort of feature so an explicit flag is used.