* Don't use dynamic_cast, it's very slow. "nix-instantiate

/etc/nixos/nixos -A system" spent about 10% of its time in
  dynamic_cast.
This commit is contained in:
Eelco Dolstra 2012-01-04 21:24:11 +00:00
parent adaf64a99b
commit 35f2a6ba82
3 changed files with 23 additions and 24 deletions

View file

@ -404,31 +404,30 @@ void EvalState::mkThunk_(Value & v, Expr * expr)
}
unsigned long nrAvoided = 0;
/* Create a thunk for the delayed computation of the given expression
in the given environment. But if the expression is a variable,
then look it up right away. This significantly reduces the number
of thunks allocated. */
Value * EvalState::maybeThunk(Env & env, Expr * expr)
Value * Expr::maybeThunk(EvalState & state, Env & env)
{
ExprVar * var;
/* Ignore variables from `withs' because they can throw an
exception. */
if ((var = dynamic_cast<ExprVar *>(expr))) {
Value * v = lookupVar(&env, var->info);
/* The value might not be initialised in the environment yet.
In that case, ignore it. */
if (v) { nrAvoided++; return v; }
}
Value * v = allocValue();
mkThunk(*v, env, expr);
Value * v = state.allocValue();
mkThunk(*v, env, this);
return v;
}
unsigned long nrAvoided = 0;
Value * ExprVar::maybeThunk(EvalState & state, Env & env)
{
Value * v = state.lookupVar(&env, info);
/* The value might not be initialised in the environment yet.
In that case, ignore it. */
if (v) { nrAvoided++; return v; }
return Expr::maybeThunk(state, env);
}
void EvalState::evalFile(const Path & path, Value & v)
{
FileEvalCache::iterator i = fileEvalCache.find(path);
@ -560,7 +559,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
vAttr = state.allocValue();
mkThunk(*vAttr, env2, i->second.e);
} else
vAttr = state.maybeThunk(env2, i->second.e);
vAttr = i->second.e->maybeThunk(state, env2);
env2.values[displ++] = vAttr;
v.attrs->push_back(Attr(i->first, vAttr, &i->second.pos));
}
@ -593,7 +592,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
if (i->second.inherited)
v.attrs->push_back(Attr(i->first, state.lookupVar(&env, i->second.var), &i->second.pos));
else
v.attrs->push_back(Attr(i->first, state.maybeThunk(env, i->second.e), &i->second.pos));
v.attrs->push_back(Attr(i->first, i->second.e->maybeThunk(state, env), &i->second.pos));
}
}
@ -613,7 +612,7 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
if (i->second.inherited)
env2.values[displ++] = state.lookupVar(&env, i->second.var);
else
env2.values[displ++] = state.maybeThunk(env2, i->second.e);
env2.values[displ++] = i->second.e->maybeThunk(state, env2);
state.eval(env2, body, v);
}
@ -623,7 +622,7 @@ void ExprList::eval(EvalState & state, Env & env, Value & v)
{
state.mkList(v, elems.size());
for (unsigned int n = 0; n < v.list.length; ++n)
v.list.elems[n] = state.maybeThunk(env, elems[n]);
v.list.elems[n] = elems[n]->maybeThunk(state, env);
}
@ -716,7 +715,7 @@ void ExprApp::eval(EvalState & state, Env & env, Value & v)
{
Value vFun;
state.eval(env, e1, vFun);
state.callFunction(vFun, *state.maybeThunk(env, e2), v);
state.callFunction(vFun, *(e2->maybeThunk(state, env)), v);
}
@ -791,7 +790,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v)
if (j == arg.attrs->end()) {
if (!i->def) throwTypeError("function at %1% called without required argument `%2%'",
fun.lambda.fun->pos, i->name);
env2.values[displ++] = maybeThunk(env2, i->def);
env2.values[displ++] = i->def->maybeThunk(*this, env2);
} else {
attrsUsed++;
env2.values[displ++] = j->value;

View file

@ -346,8 +346,6 @@ public:
void mkAttrs(Value & v, unsigned int expected);
void mkThunk_(Value & v, Expr * expr);
Value * maybeThunk(Env & env, Expr * expr);
/* Print statistics. */
void printStats();

View file

@ -53,6 +53,7 @@ struct Expr
virtual void show(std::ostream & str);
virtual void bindVars(const StaticEnv & env);
virtual void eval(EvalState & state, Env & env, Value & v);
virtual Value * maybeThunk(EvalState & state, Env & env);
};
std::ostream & operator << (std::ostream & str, Expr & e);
@ -117,6 +118,7 @@ struct ExprVar : Expr
VarRef info;
ExprVar(const Symbol & name) : info(name) { };
COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
};
struct ExprSelect : Expr