forked from lix-project/lix
Merge pull request #9681 from edolstra/eval-optimisations
Optimize empty list constants
(cherry picked from commit 315aade89d00c692715e5953c36a1b7d6528b703)
Change-Id: I0f28ef8a27ccedc45acf44243eec9dc35b733300
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6b279cd10e
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@ -527,6 +527,8 @@ EvalState::EvalState(
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static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
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vEmptyList.mkList(0);
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/* Initialise the Nix expression search path. */
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if (!evalSettings.pureEval) {
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for (auto & i : _searchPath.elements)
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@ -1405,6 +1407,15 @@ void ExprList::eval(EvalState & state, Env & env, Value & v)
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}
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Value * ExprList::maybeThunk(EvalState & state, Env & env)
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{
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if (elems.empty()) {
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return &state.vEmptyList;
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}
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return Expr::maybeThunk(state, env);
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}
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void ExprVar::eval(EvalState & state, Env & env, Value & v)
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{
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Value * v2 = state.lookupVar(&env, *this, false);
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@ -218,6 +218,11 @@ public:
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Bindings emptyBindings;
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/**
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* Empty list constant.
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*/
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Value vEmptyList;
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const SourcePath derivationInternal;
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/**
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@ -298,6 +298,7 @@ struct ExprList : Expr
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std::vector<Expr *> elems;
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ExprList() { };
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COMMON_METHODS
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Value * maybeThunk(EvalState & state, Env & env) override;
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PosIdx getPos() const override
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{
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