A handful of optimizations for the DRC collector#12974
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fitzgen wants to merge 7 commits intobytecodealliance:mainfrom
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A handful of optimizations for the DRC collector#12974fitzgen wants to merge 7 commits intobytecodealliance:mainfrom
fitzgen wants to merge 7 commits intobytecodealliance:mainfrom
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Also add fast-path entry points that take a `u32` size directly that has already been rounded to the free list's alignment. Altogether, this shaves off ~309B instructions retired (48%) from the benchmark in bytecodealliance#11141
Ideally we would just use a `SecondaryMap<VMSharedTypeIndex, TraceInfo>` here but allocating `O(num engine types)` space inside a store that uses only a couple types seems not great. So instead, we just have a fixed size cache that is probably big enough for most things in practice.
Inline `dec_ref`, `trace_gc_ref`, and `dealloc` into `dec_ref_and_maybe_dealloc`'s main loop so that we read the `VMDrcHeader` once per object to get `ref_count`, type index, and `object_size`, avoiding 3 separate GC heap accesses and bounds checks per freed object. For struct tracing, read gc_ref fields directly from the heap slice at known offsets instead of going through gc_object_data → object_range → object_size which would re-read the object_size from the header. 301,333,979,721 -> 291,038,676,119 instructions (~3.4% improvement)
…exists When the GC store is already initialized and the allocation succeeds, avoid async machinery entirely. This avoids the overhead of taking/restoring fiber async state pointers on every allocation. 291,038,676,119 -> 230,503,364,489 instructions (~20.8% improvement)
Avoids converting `ModuleInternedTypeIndex` to `VMSharedTypeIndex` in host code, which requires look ups in the instance's module's `TypeCollection`. We already have helpers to do this conversion inline in JIT code. 230,503,364,489 -> 216,937,168,529 instructions (~5.9% improvement)
Moves the `externref` host data cleanup inside the `ty.is_none()` branch of `dec_ref_and_maybe_dealloc`, since only `externref`s have host data. Additionally the type check is sort of expensive since it involves additional bounds-checked reads from the GC heap.
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Depends on #12969
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