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

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

View file

@ -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);
}

View file

@ -106,6 +106,7 @@ struct Value
struct Env
{
Env * up;
unsigned int prevWith; // nr of levels up to next `with' environment
Value values[0];
};

View file

@ -278,12 +278,12 @@ void ExprLet::bindVars(const StaticEnv & env)
void ExprWith::bindVars(const StaticEnv & env)
{
/* Does this `with' have an enclosing `with'? If so, record its
level so that we can copy the attributes of the enclosing
`with'. */
level so that `lookupVar' can look up variables in the previous
`with' if this one doesn't contain the desired attribute. */
const StaticEnv * curEnv;
unsigned int level;
prevWith = -1;
for (curEnv = &env, level = 0; curEnv; curEnv = curEnv->up, level++)
prevWith = 0;
for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
if (curEnv->isWith) {
prevWith = level;
break;

View file

@ -184,7 +184,7 @@ struct ExprWith : Expr
{
Pos pos;
Expr * attrs, * body;
int prevWith;
unsigned int prevWith;
ExprWith(const Pos & pos, Expr * attrs, Expr * body) : pos(pos), attrs(attrs), body(body) { };
COMMON_METHODS
};