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* After parsing, compute level/displacement pairs for each variable

Browse source 
use site, allowing environments to be stores as vectors of values
  rather than maps.  This should speed up evaluation and reduce the
  number of allocations.
This commit is contained in:
Eelco Dolstra 2010-04-14 14:42:32 +00:00
parent 816dd3f061
commit 9985230c00
7 changed files with 258 additions and 143 deletions
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5
src/libexpr/eval-test.cc
View file

@ -51,11 +51,12 @@ void run(Strings args)
printMsg(lvlError, format("size of value: %1% bytes") % sizeof(Value));
printMsg(lvlError, format("size of int AST node: %1% bytes") % sizeof(ExprInt));
printMsg(lvlError, format("size of attrset AST node: %1% bytes") % sizeof(ExprAttrs));
doTest(state, "123");
doTest(state, "{ x = 1; y = 2; }");
doTest(state, "{ x = 1; y = 2; }.y");
doTest(state, "rec { x = 1; y = x; }.y");
doTest(state, "let x = 1; y = 2; z = 3; in let a = 4; in y");
doTest(state, "rec { x = 1; y = x; }.x");
doTest(state, "(x: x) 1");
doTest(state, "(x: y: y) 1 2");
doTest(state, "x: x");

91
src/libexpr/eval.cc
View file

@ -98,7 +98,7 @@ EvalState::EvalState()
, sType(symbols.create("type"))
, sMeta(symbols.create("meta"))
, sName(symbols.create("name"))
, baseEnv(allocEnv())
, baseEnv(allocEnv(128))
{
nrValues = nrEnvs = nrEvaluated = recursionDepth = maxRecursionDepth = 0;
deepestStack = (char *) -1;
@ -117,16 +117,19 @@ EvalState::~EvalState()
void EvalState::addConstant(const string & name, Value & v)
{
#if 0
baseEnv.bindings[symbols.create(name)] = v;
string name2 = string(name, 0, 2) == "__" ? string(name, 2) : name;
(*baseEnv.bindings[symbols.create("builtins")].attrs)[symbols.create(name2)] = v;
nrValues += 2;
#endif
}
void EvalState::addPrimOp(const string & name,
unsigned int arity, PrimOp primOp)
{
#if 0
Value v;
v.type = tPrimOp;
v.primOp.arity = arity;
@ -135,6 +138,7 @@ void EvalState::addPrimOp(const string & name,
string name2 = string(name, 0, 2) == "__" ? string(name, 2) : name;
(*baseEnv.bindings[symbols.create("builtins")].attrs)[symbols.create(name2)] = v;
nrValues += 2;
#endif
}
@ -234,8 +238,8 @@ void mkPath(Value & v, const char * s)
Value * EvalState::lookupVar(Env * env, const Symbol & name)
{
#if 0
/* First look for a regular variable binding for `name'. */
for (Env * env2 = env; env2; env2 = env2->up) {
Bindings::iterator i = env2->bindings.find(name);
if (i != env2->bindings.end()) return &i->second;
}
@ -250,7 +254,8 @@ Value * EvalState::lookupVar(Env * env, const Symbol & name)
if (j != i->second.attrs->end()) return &j->second;
}
throwEvalError("undefined variable `%1%'", name);
throwEvalError("urgh! undefined variable `%1%'", name);
#endif
}
@ -261,10 +266,11 @@ Value * EvalState::allocValues(unsigned int count)
}
Env & EvalState::allocEnv()
Env & EvalState::allocEnv(unsigned int size)
{
nrEnvs++;
return *(new Env);
Env * env = (Env *) malloc(sizeof(Env) + size * sizeof(Value));
return *env;
}
@ -343,7 +349,7 @@ void EvalState::eval(Env & env, Expr * e, Value & v)
char x;
if (&x < deepestStack) deepestStack = &x;
//debug(format("eval: %1%") % *e);
debug(format("eval: %1%") % *e);
checkInterrupt();
@ -396,28 +402,33 @@ void ExprPath::eval(EvalState & state, Env & env, Value & v)
void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
{
if (recursive) {
/* Create a new environment that contains the attributes in
this `rec'. */
Env & env2(state.allocEnv());
Env & env2(state.allocEnv(attrs.size() + inherited.size()));
env2.up = &env;
v.type = tAttrs;
v.attrs = &env2.bindings;
v.attrs = new Bindings;
unsigned int displ = 0;
/* The recursive attributes are evaluated in the new
environment. */
foreach (Attrs::iterator, i, attrs) {
Value & v2 = env2.bindings[i->first];
mkThunk(v2, env2, i->second);
Value & v2 = (*v.attrs)[i->first];
mkCopy(v2, env2.values[displ]);
mkThunk(env2.values[displ++], env2, i->second);
}
#if 0
/* The inherited attributes, on the other hand, are
evaluated in the original environment. */
foreach (list<Symbol>::iterator, i, inherited) {
Value & v2 = env2.bindings[*i];
mkCopy(v2, *state.lookupVar(&env, *i));
}
#endif
}
else {
@ -439,22 +450,24 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
{
/* Create a new environment that contains the attributes in this
`let'. */
Env & env2(state.allocEnv());
Env & env2(state.allocEnv(attrs->attrs.size() + attrs->inherited.size()));
env2.up = &env;
unsigned int displ = 0;
/* The recursive attributes are evaluated in the new
environment. */
foreach (ExprAttrs::Attrs::iterator, i, attrs->attrs) {
Value & v2 = env2.bindings[i->first];
mkThunk(v2, env2, i->second);
}
foreach (ExprAttrs::Attrs::iterator, i, attrs->attrs)
mkThunk(env2.values[displ++], env2, i->second);
#if 0
/* The inherited attributes, on the other hand, are evaluated in
the original environment. */
foreach (list<Symbol>::iterator, i, attrs->inherited) {
Value & v2 = env2.bindings[*i];
mkCopy(v2, *state.lookupVar(&env, *i));
}
#endif
state.eval(env2, body, v);
}
@ -470,9 +483,16 @@ void ExprList::eval(EvalState & state, Env & env, Value & v)
void ExprVar::eval(EvalState & state, Env & env, Value & v)
{
Value * v2 = state.lookupVar(&env, name);
state.forceValue(*v2);
v = *v2;
printMsg(lvlError, format("eval var %1% %2% %3%") % fromWith % level % displ);
if (fromWith) {
abort();
} else {
Env * env2 = &env;
for (unsigned int l = level; l; --l, env2 = env2->up) ;
state.forceValue(env2->values[displ]);
v = env2->values[displ];
}
}
@ -559,22 +579,22 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v)
throwTypeError("attempt to call something which is neither a function nor a primop (built-in operation) but %1%",
showType(fun));
Env & env2(allocEnv());
unsigned int size =
(fun.lambda.fun->arg.empty() ? 0 : 1) +
(fun.lambda.fun->matchAttrs ? fun.lambda.fun->formals->formals.size() : 0);
Env & env2(allocEnv(size));
env2.up = fun.lambda.env;
if (!fun.lambda.fun->matchAttrs) {
Value & vArg = env2.bindings[fun.lambda.fun->arg];
nrValues++;
vArg = arg;
}
unsigned int displ = 0;
if (!fun.lambda.fun->matchAttrs)
env2.values[displ++] = arg;
else {
forceAttrs(arg);
if (!fun.lambda.fun->arg.empty()) {
env2.bindings[fun.lambda.fun->arg] = arg;
nrValues++;
}
if (!fun.lambda.fun->arg.empty())
env2.values[displ++] = arg;
/* For each formal argument, get the actual argument. If
there is no matching actual argument but the formal
@ -582,17 +602,13 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v)
unsigned int attrsUsed = 0;
foreach (Formals::Formals_::iterator, i, fun.lambda.fun->formals->formals) {
Bindings::iterator j = arg.attrs->find(i->name);
Value & v = env2.bindings[i->name];
nrValues++;
if (j == arg.attrs->end()) {
if (!i->def) throwTypeError("function at %1% called without required argument `%2%'",
fun.lambda.fun->pos, i->name);
mkThunk(v, env2, i->def);
mkThunk(env2.values[displ++], env2, i->def);
} else {
attrsUsed++;
mkCopy(v, j->second);
mkCopy(env2.values[displ++], j->second);
}
}
@ -639,6 +655,8 @@ void EvalState::autoCallFunction(const Bindings & args, Value & fun, Value & res
void ExprWith::eval(EvalState & state, Env & env, Value & v)
{
abort();
#if 0
Env & env2(state.allocEnv());
env2.up = &env;
@ -647,6 +665,7 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
state.forceAttrs(vAttrs);
state.eval(env2, body, v);
#endif
}

16
src/libexpr/eval.hh
View file

@ -18,13 +18,6 @@ struct Value;
typedef std::map<Symbol, Value> Bindings;
struct Env
{
Env * up;
Bindings bindings;
};
typedef enum {
tInt = 1,
tBool,
@ -109,6 +102,13 @@ struct Value
};
struct Env
{
Env * up;
Value values[0];
};
static inline void mkInt(Value & v, int n)
{
v.type = tInt;
@ -258,7 +258,7 @@ public:
/* Allocation primitives. */
Value * allocValues(unsigned int count);
Env & allocEnv();
Env & allocEnv(unsigned int size);
void mkList(Value & v, unsigned int length);
void mkAttrs(Value & v);

234
src/libexpr/nixexpr.cc
View file

@ -8,13 +8,14 @@
namespace nix {
/* Displaying abstract syntax trees. */
std::ostream & operator << (std::ostream & str, Expr & e)
{
e.show(str);
return str;
}
void Expr::show(std::ostream & str)
{
abort();
@ -135,103 +136,162 @@ std::ostream & operator << (std::ostream & str, const Pos & pos)
str << (format("`%1%:%2%:%3%'") % pos.file % pos.line % pos.column).str();
return str;
}
#if 0
static void varsBoundByPattern(ATermMap & map, Pattern pat)
/* Computing levels/displacements for variables. */
void Expr::bindVars(const StaticEnv & env)
{
ATerm name;
ATermList formals;
ATermBool ellipsis;
/* Use makeRemoved() so that it can be used directly in
substitute(). */
if (matchVarPat(pat, name))
map.set(name, makeRemoved());
else if (matchAttrsPat(pat, formals, ellipsis, name)) {
if (name != sNoAlias) map.set(name, makeRemoved());
for (ATermIterator i(formals); i; ++i) {
ATerm d1;
if (!matchFormal(*i, name, d1)) abort();
map.set(name, makeRemoved());
abort();
}
void ExprInt::bindVars(const StaticEnv & env)
{
}
void ExprString::bindVars(const StaticEnv & env)
{
}
void ExprPath::bindVars(const StaticEnv & env)
{
}
void ExprVar::bindVars(const StaticEnv & env)
{
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
const StaticEnv * curEnv;
unsigned int level;
int withLevel = -1;
for (curEnv = &env, level = 0; curEnv; curEnv = curEnv->up, level++) {
if (curEnv->isWith) {
if (withLevel == -1) withLevel = level;
} else {
StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
if (i != curEnv->vars.end()) {
fromWith = false;
this->level = level;
displ = i->second;
return;
}
}
}
else abort();
/* Otherwise, the variable must be obtained from the nearest
enclosing `with'. If there is no `with', then we can issue an
"undefined variable" error now. */
if (withLevel == -1) throw EvalError(format("undefined variable `%1%'") % name);
fromWith = true;
this->level = withLevel;
}
/* We use memoisation to prevent exponential complexity on heavily
shared ATerms (remember, an ATerm is a graph, not a tree!). Note
that using an STL set is fine here wrt to ATerm garbage collection
since all the ATerms in the set are already reachable from
somewhere else. */
static void checkVarDefs2(set<Expr> & done, const ATermMap & defs, Expr e)
void ExprSelect::bindVars(const StaticEnv & env)
{
if (done.find(e) != done.end()) return;
done.insert(e);
ATerm name, pos, value;
ATerm with, body;
ATermList rbnds, nrbnds;
Pattern pat;
/* Closed terms don't have free variables, so we don't have to
check by definition. */
if (matchClosed(e, value)) return;
else if (matchVar(e, name)) {
if (!defs.get(name))
throw EvalError(format("undefined variable `%1%'")
% aterm2String(name));
}
else if (matchFunction(e, pat, body, pos)) {
ATermMap defs2(defs);
varsBoundByPattern(defs2, pat);
set<Expr> done2;
checkVarDefs2(done2, defs2, pat);
checkVarDefs2(done2, defs2, body);
}
else if (matchRec(e, rbnds, nrbnds)) {
checkVarDefs2(done, defs, (ATerm) nrbnds);
ATermMap defs2(defs);
for (ATermIterator i(rbnds); i; ++i) {
if (!matchBind(*i, name, value, pos)) abort(); /* can't happen */
defs2.set(name, (ATerm) ATempty);
}
for (ATermIterator i(nrbnds); i; ++i) {
if (!matchBind(*i, name, value, pos)) abort(); /* can't happen */
defs2.set(name, (ATerm) ATempty);
}
set<Expr> done2;
checkVarDefs2(done2, defs2, (ATerm) rbnds);
}
else if (matchWith(e, with, body, pos)) {
/* We can't check the body without evaluating the definitions
(which is an arbitrary expression), so we don't do that
here but only when actually evaluating the `with'. */
checkVarDefs2(done, defs, with);
}
else if (ATgetType(e) == AT_APPL) {
int arity = ATgetArity(ATgetAFun(e));
for (int i = 0; i < arity; ++i)
checkVarDefs2(done, defs, ATgetArgument(e, i));
}
else if (ATgetType(e) == AT_LIST)
for (ATermIterator i((ATermList) e); i; ++i)
checkVarDefs2(done, defs, *i);
e->bindVars(env);
}
void checkVarDefs(const ATermMap & defs, Expr e)
void ExprOpHasAttr::bindVars(const StaticEnv & env)
{
set<Expr> done;
checkVarDefs2(done, defs, e);
e->bindVars(env);
}
void ExprAttrs::bindVars(const StaticEnv & env)
{
if (recursive) {
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
foreach (ExprAttrs::Attrs::iterator, i, attrs)
newEnv.vars[i->first] = displ++;
foreach (list<Symbol>::iterator, i, inherited)
newEnv.vars[*i] = displ++;
foreach (ExprAttrs::Attrs::iterator, i, attrs)
i->second->bindVars(newEnv);
}
else
foreach (ExprAttrs::Attrs::iterator, i, attrs)
i->second->bindVars(env);
}
void ExprList::bindVars(const StaticEnv & env)
{
foreach (vector<Expr *>::iterator, i, elems)
(*i)->bindVars(env);
}
void ExprLambda::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
if (!arg.empty()) newEnv.vars[arg] = displ++;
if (matchAttrs) {
foreach (Formals::Formals_::iterator, i, formals->formals)
newEnv.vars[i->name] = displ++;
foreach (Formals::Formals_::iterator, i, formals->formals)
if (i->def) i->def->bindVars(newEnv);
}
body->bindVars(newEnv);
}
void ExprLet::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
foreach (ExprAttrs::Attrs::iterator, i, attrs->attrs)
newEnv.vars[i->first] = displ++;
foreach (list<Symbol>::iterator, i, attrs->inherited)
newEnv.vars[*i] = displ++;
foreach (ExprAttrs::Attrs::iterator, i, attrs->attrs)
i->second->bindVars(newEnv);
body->bindVars(newEnv);
}
void ExprWith::bindVars(const StaticEnv & env)
{
attrs->bindVars(env);
StaticEnv newEnv(true, &env);
body->bindVars(newEnv);
}
void ExprIf::bindVars(const StaticEnv & env)
{
cond->bindVars(env);
then->bindVars(env);
else_->bindVars(env);
}
void ExprAssert::bindVars(const StaticEnv & env)
{
cond->bindVars(env);
body->bindVars(env);
}
void ExprOpNot::bindVars(const StaticEnv & env)
{
e->bindVars(env);
}
void ExprConcatStrings::bindVars(const StaticEnv & env)
{
foreach (vector<Expr *>::iterator, i, *es)
(*i)->bindVars(env);
}
#endif
}

48
src/libexpr/nixexpr.hh
View file

@ -17,25 +17,29 @@ MakeError(Abort, EvalError)
MakeError(TypeError, EvalError)
/* Position objects. */
struct Pos
{
string file;
unsigned int line, column;
};
std::ostream & operator << (std::ostream & str, const Pos & pos);
/* Abstract syntax of Nix expressions. */
struct Env;
struct Value;
struct EvalState;
struct StaticEnv;
/* Abstract syntax of Nix expressions. */
struct Expr
{
virtual void show(std::ostream & str);
virtual void bindVars(const StaticEnv & env);
virtual void eval(EvalState & state, Env & env, Value & v);
};
@ -43,7 +47,8 @@ std::ostream & operator << (std::ostream & str, Expr & e);
#define COMMON_METHODS \
void show(std::ostream & str); \
void eval(EvalState & state, Env & env, Value & v);
void eval(EvalState & state, Env & env, Value & v); \
void bindVars(const StaticEnv & env);
struct ExprInt : Expr
{
@ -76,6 +81,20 @@ struct ExprPath : Expr
struct ExprVar : Expr
{
Symbol name;
/* Whether the variable comes from an environment (e.g. a rec, let
or function argument) or from a "with". */
bool fromWith;
/* In the former case, the value is obtained by going `level'
levels up from the current environment and getting the
`displ'th value in that environment. In the latter case, the
value is obtained by getting the attribute named `name' from
the attribute set stored in the environment that is `level'
levels up from the current one.*/
unsigned int level;
unsigned int displ;
ExprVar(const Symbol & name) : name(name) { };
COMMON_METHODS
};
@ -186,6 +205,10 @@ struct ExprOpNot : Expr
{ \
str << *e1 << " " s " " << *e2; \
} \
void bindVars(const StaticEnv & env) \
{ \
e1->bindVars(env); e2->bindVars(env); \
} \
void eval(EvalState & state, Env & env, Value & v); \
};
@ -206,11 +229,18 @@ struct ExprConcatStrings : Expr
};
#if 0
/* Check whether all variables are defined in the given expression.
Throw an exception if this isn't the case. */
void checkVarDefs(const ATermMap & def, Expr e);
#endif
/* Static environments are used to map variable names onto (level,
displacement) pairs used to obtain the value of the variable at
runtime. */
struct StaticEnv
{
bool isWith;
const StaticEnv * up;
typedef std::map<Symbol, unsigned int> Vars;
Vars vars;
StaticEnv(bool isWith, const StaticEnv * up) : isWith(isWith), up(up) { };
};
}

3
src/libexpr/parser.y
View file

@ -461,7 +461,8 @@ static Expr * parse(EvalState & state, const char * text,
if (res) throw ParseError(data.error);
try {
// !!! checkVarDefs(state.primOps, data.result);
StaticEnv env(false, 0);
data.result->bindVars(env);
} catch (Error & e) {
throw ParseError(format("%1%, in `%2%'") % e.msg() % path);
}

4
src/libexpr/primops.cc
View file

@ -999,9 +999,11 @@ void EvalState::createBaseEnv()
{
baseEnv.up = 0;
#if 0
Value & builtins = baseEnv.bindings[symbols.create("builtins")];
builtins.type = tAttrs;
builtins.attrs = new Bindings;
#endif
/* Add global constants such as `true' to the base environment. */
Value v;
@ -1023,9 +1025,11 @@ void EvalState::createBaseEnv()
/* Add a wrapper around the derivation primop that computes the
`drvPath' and `outPath' attributes lazily. */
#if 0
string s = "attrs: let res = derivationStrict attrs; in attrs // { drvPath = res.drvPath; outPath = res.outPath; type = \"derivation\"; }";
mkThunk(v, baseEnv, parseExprFromString(*this, s, "/"));
addConstant("derivation", v);
#endif
// Miscellaneous
addPrimOp("import", 1, prim_import);