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* Simplify the implementation of `with'. This gives a 7% speedup in

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evaluating the NixOS system configuration.
This commit is contained in:
Eelco Dolstra 2010-04-22 15:08:09 +00:00
parent ee0384fb96
commit 0bc468f195
4 changed files with 15 additions and 30 deletions
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34
src/libexpr/eval.cc
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@ -246,10 +246,14 @@ Value * EvalState::lookupVar(Env * env, const VarRef & var)
for (unsigned int l = var.level; l; --l, env = env->up) ;
if (var.fromWith) {
Bindings::iterator j = env->values[0].attrs->find(var.name);
if (j == env->values[0].attrs->end())
throwEvalError("undefined variable `%1%'", var.name);
return &j->second;
while (1) {
Bindings::iterator j = env->values[0].attrs->find(var.name);
if (j != env->values[0].attrs->end())
return &j->second;
if (env->prevWith == 0)
throwEvalError("undefined variable `%1%'", var.name);
for (unsigned int l = env->prevWith; l; --l, env = env->up) ;
}
} else
return &env->values[var.displ];
}
@ -656,30 +660,10 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
{
Env & env2(state.allocEnv(1));
env2.up = &env;
env2.prevWith = prevWith;
state.evalAttrs(env, attrs, env2.values[0]);
/* If there is an enclosing `with', copy all attributes that don't
appear in this `with'. */
if (prevWith != -1) {
Env * env3 = &env;
for (unsigned int l = prevWith; l; --l, env3 = env3->up) ;
/* Because the first `with' may be a shallow copy of another
attribute set (through a tCopy node), we need to clone its
`attrs' before modifying them. */
Bindings * old(env2.values[0].attrs);
state.mkAttrs(env2.values[0]);
foreach (Bindings::iterator, i, *old)
mkCopy((*env2.values[0].attrs)[i->first], i->second);
foreach (Bindings::iterator, i, *env3->values[0].attrs) {
Bindings::iterator j = env2.values[0].attrs->find(i->first);
if (j == env2.values[0].attrs->end())
mkCopy((*env2.values[0].attrs)[i->first], i->second);
}
}
state.eval(env2, body, v);
}