RFC 0004: HEAP escape analysis #4
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Add an optimization pass to the compiler to detect places where a class instantiation could happen on the stack rather than the GC HEAP.
ysbaddaden
commented
Feb 6, 2024
Co-authored-by: Johannes Müller <straightshoota@gmail.com>
RX14
reviewed
Feb 7, 2024
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| # Drawbacks | ||
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| Some objects would now be allocated on the stack, which are GC roots that must be scanned conservatively and can't scan precisely. This may have negatively impact GC performance when we implement semi-conservative marking (conservative marking of GC roots _yet_ precise marking of HEAP allocated objects). |
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I think it might be possible to reuse a lot of the escape analysis architecture to implement a shadow stack for each fiber which contains only roots. This could be both precise and a far smaller stack than the actual program stack for the GC to scan. Especially given the stack usage will grow when escape analysis is turned on.
I don't know how that tradeoff compares to the LLVM built in stackmap generator, but it's an idea.
straight-shoota
changed the title
yxhuvud
reviewed
Feb 23, 2024
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Add an optimization pass to the compiler to detect places where a class instantiation could happen on the stack rather than the GC HEAP.
Preview: https://github.com/crystal-lang/rfcs/blob/rfc-heap-escape-analysis/text/0004-heap-escape-analysis.md