eldritch horrors
80654b84b6
thunk values are shareable, and we can represent invalid/uninitialized values with a special bit pattern that makes no sense otherwise. there is no need to keep allocating values on the heap, instead we can treat values like reference-counted smart pointers to heap objects, which in turn lets us save a lot of allocations and, ultimately, gc heap space. compared to our baseline (main of 2025-09-27) we save 15%+ memory on a system rebuild and 17% on nix search. eval time regresses by ~3% for a system rebuild, while nix search is 7% faster. further optimization is probably possible (but for now this will just have to be good enough). Change-Id: Ib6c47acdbe2fac4f76a83c2269f16f30ef66b2e1
54 lines
1.1 KiB
C++
54 lines
1.1 KiB
C++
#include "lix/libexpr/attr-set.hh"
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#include "lix/libexpr/eval.hh"
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#include "lix/libexpr/gc-alloc.hh"
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#include <algorithm>
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namespace nix {
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Bindings Bindings::EMPTY{};
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/* Allocate a new array of attributes for an attribute set with a specific
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capacity. The space is implicitly reserved after the Bindings
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structure. */
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Bindings * EvalMemory::allocBindings(size_t capacity)
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{
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if (capacity == 0)
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return &Bindings::EMPTY;
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if (capacity > std::numeric_limits<Bindings::Size>::max())
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throw Error("attribute set of size %d is too big", capacity);
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stats.nrAttrsets++;
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stats.nrAttrsInAttrsets += capacity;
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return new (allocBytes(sizeof(Bindings) + sizeof(Attr) * capacity)) Bindings();
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}
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Value & BindingsBuilder::alloc(Symbol name, PosIdx pos)
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{
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bindings->push_back(Attr(name, {}, pos));
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return (bindings->end() - 1)->value;
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}
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Value & BindingsBuilder::alloc(std::string_view name, PosIdx pos)
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{
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return alloc(symbols.create(name), pos);
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}
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void Bindings::sort()
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{
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if (size_) std::sort(begin(), end());
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}
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Value & Value::mkAttrs(BindingsBuilder & bindings)
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{
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mkAttrs(bindings.finish());
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return *this;
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}
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}
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