Light(er)weight SWT. #291
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Light(er)weight SWT. #291
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vext01
commented
Dec 3, 2025
| // tracing_check: | ||
| // %t <- load the "is this thread tracing?" thread local | ||
| // %dont_record <- t == 0 | ||
| // condbr %t, record, done |
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Just realised that the arguments on this are wrong.
This changes the software tracing pass so that we do the "is the thread
tracing?" check inline in the interpreter AOT code, instead of calling
out to Rust every time to do the check.
The AOT IR serialiser is then modified so as to give the JIT runtime the
IR as though the checks didn't exist. This is because:
- a) we don't ever want to trace the checks, so they are just IR bloat.
- b) it would be laborious to filter out the checks when building the
trace, and the more we can do statically the better.
Measurement suggests small speedups in the order of a few percent points
for a handful of benchmarks, but this is (hopefully) only the beginning
of what can be done. There are many optimisations we plan to do which
*should* compound.
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This changes the software tracing pass so that we do the "is the thread tracing?" check inline in the interpreter AOT code, instead of calling out to Rust every time to do the check.
The AOT IR serialiser is then modified so as to give the JIT runtime the IR as though the checks didn't exist. This is because:
a) we don't ever want to trace the checks, so they are just IR bloat.
b) it would be laborious to filter out the checks when building the trace, and the more we can do statically the better.
Measurement suggests small speedups in the order of a few percent points for a handful of benchmarks, but this is (hopefully) only the beginning of what can be done. There are many optimisations we plan to do which should compound.