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https://github.com/NixOS/nix
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78353deb02
checking for isBlackhole in the forceValue hot path is rather more
expensive than necessary, and with a little bit of trickery we can move
such handling into the isApp case. small performance benefit, but under
some circumstances we've seen 2% improvement as well.
〉 nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
before:
Time (mean ± σ): 4.429 s ± 0.002 s [User: 3.929 s, System: 0.500 s]
Range (min … max): 4.427 s … 4.433 s 10 runs
after:
Time (mean ± σ): 4.396 s ± 0.002 s [User: 3.894 s, System: 0.501 s]
Range (min … max): 4.393 s … 4.399 s 10 runs
60 lines
1.6 KiB
C++
60 lines
1.6 KiB
C++
#pragma once
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///@file
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#include "eval.hh"
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#include <tuple>
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#include <vector>
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namespace nix {
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/**
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* For functions where we do not expect deep recursion, we can use a sizable
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* part of the stack a free allocation space.
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*
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* Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
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*/
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constexpr size_t nonRecursiveStackReservation = 128;
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/**
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* Functions that maybe applied to self-similar inputs, such as concatMap on a
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* tree, should reserve a smaller part of the stack for allocation.
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*
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* Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
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*/
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constexpr size_t conservativeStackReservation = 16;
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struct RegisterPrimOp
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{
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typedef std::vector<PrimOp> PrimOps;
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static PrimOps * primOps;
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/**
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* You can register a constant by passing an arity of 0. fun
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* will get called during EvalState initialization, so there
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* may be primops not yet added and builtins is not yet sorted.
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*/
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RegisterPrimOp(PrimOp && primOp);
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};
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/* These primops are disabled without enableNativeCode, but plugins
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may wish to use them in limited contexts without globally enabling
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them. */
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/**
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* Load a ValueInitializer from a DSO and return whatever it initializes
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*/
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void prim_importNative(EvalState & state, const PosIdx pos, Value * * args, Value & v);
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/**
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* Execute a program and parse its output
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*/
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void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v);
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/**
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* Placeholder value for black holes, used to represent black holes as
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* applications of this value to the evaluated thunks.
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*/
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extern Value prim_blackHole;
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}
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