Merge pull request #9681 from edolstra/eval-optimisations

Optimize empty list constants

(cherry picked from commit 315aade89d00c692715e5953c36a1b7d6528b703)
Change-Id: I0f28ef8a27ccedc45acf44243eec9dc35b733300
This commit is contained in:
eldritch horrors 2024-03-04 07:39:12 +01:00
parent 6b279cd10e
commit 137673de56
3 changed files with 17 additions and 0 deletions

View file

@ -527,6 +527,8 @@ EvalState::EvalState(
static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes"); static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
vEmptyList.mkList(0);
/* Initialise the Nix expression search path. */ /* Initialise the Nix expression search path. */
if (!evalSettings.pureEval) { if (!evalSettings.pureEval) {
for (auto & i : _searchPath.elements) for (auto & i : _searchPath.elements)
@ -1405,6 +1407,15 @@ 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) void ExprVar::eval(EvalState & state, Env & env, Value & v)
{ {
Value * v2 = state.lookupVar(&env, *this, false); Value * v2 = state.lookupVar(&env, *this, false);

View file

@ -218,6 +218,11 @@ public:
Bindings emptyBindings; Bindings emptyBindings;
/**
* Empty list constant.
*/
Value vEmptyList;
const SourcePath derivationInternal; const SourcePath derivationInternal;
/** /**

View file

@ -298,6 +298,7 @@ struct ExprList : Expr
std::vector<Expr *> elems; std::vector<Expr *> elems;
ExprList() { }; ExprList() { };
COMMON_METHODS COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env) override;
PosIdx getPos() const override PosIdx getPos() const override
{ {