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Merge pull request #9681 from edolstra/eval-optimisations

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Optimize empty list constants
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Eelco Dolstra 2024-01-03 10:43:01 +01:00 committed by GitHub
parent f5b97f1958 484881f302
commit 315aade89d
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3 changed files with 17 additions and 0 deletions
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11
src/libexpr/eval.cc
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@ -554,6 +554,8 @@ EvalState::EvalState(
static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
vEmptyList.mkList(0);
/* Initialise the Nix expression search path. */
if (!evalSettings.pureEval) {
for (auto & i : _searchPath.elements)
@ -1385,6 +1387,15 @@ void ExprList::eval(EvalState & state, Env & env, Value & v)
}
Value * ExprList::maybeThunk(EvalState & state, Env & env)
{
if (elems.empty()) {
return &state.vEmptyList;
}
return Expr::maybeThunk(state, env);
}
void ExprVar::eval(EvalState & state, Env & env, Value & v)
{
Value * v2 = state.lookupVar(&env, *this, false);

5
src/libexpr/eval.hh
View file

@ -213,6 +213,11 @@ public:
Bindings emptyBindings;
/**
* Empty list constant.
*/
Value vEmptyList;
/**
* The accessor for the root filesystem.
*/

1
src/libexpr/nixexpr.hh
View file

@ -303,6 +303,7 @@ struct ExprList : Expr
std::vector<Expr *> elems;
ExprList() { };
COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env) override;
PosIdx getPos() const override
{