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YJIT: Skip defer_compilation for fixnums if possible #7168

Merged
merged 3 commits into from
Jan 30, 2023
Merged

YJIT: Skip defer_compilation for fixnums if possible #7168

merged 3 commits into from
Jan 30, 2023

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k0kubun
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@k0kubun k0kubun commented Jan 21, 2023 •
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This partly addresses Shopify#462.

When "compile-time stack-top values are fixnums?" can be answered from the type info in ctx, this PR skips defer_compilation.

As investigated in Shopify#462 (comment), it's not supposed to have a huge impact on the number of blocks. However, as I started experimenting with register allocation, targeting only intra-block allocation as a first step, I noticed even very simple blocks are split now. Supporting this is useful for that first milestone and I figured the implementation is not that complicated.

Impact

It does have a small impact though. It eliminates some unneeded blocks on railsbench, reducing Rust memory consumption from 9.01MB to 9.00MB.

Before

compiled_block_count:       20739
defer_count:                 6871
code_region_size:         6733824
yjit_alloc_size:          9010417

After

compiled_block_count:       20699
defer_count:                 6836
code_region_size:         6733824
yjit_alloc_size:          9500787

@matzbot matzbot requested a review from a team January 21, 2023 00:49
noahgibbs
noahgibbs reviewed Jan 23, 2023
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yjit/src/codegen.rs Outdated Show resolved Hide resolved
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This looks like a good idea to me, and unlikely to cause problems.

maximecb
maximecb reviewed Jan 23, 2023
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@k0kubun k0kubun requested a review from a team January 30, 2023 17:01
@k0kubun k0kubun mentioned this pull request Jan 30, 2023
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@maximecb maximecb merged commit bc0dc9d into ruby:master Jan 30, 2023
@maximecb maximecb deleted the yjit-skip-defer branch January 30, 2023 18:55
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@k0kubun @noahgibbs @maximecb