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Optimize small lists

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The value pointers of lists with 1 or 2 elements are now stored in the
list value itself. In particular, this makes the "concatMap (x: if
cond then [(f x)] else [])" idiom cheaper.
This commit is contained in:
Eelco Dolstra 2015-07-23 22:05:09 +02:00
parent 14be783676
commit b83801f8b3
11 changed files with 157 additions and 121 deletions
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29
src/libexpr/value.hh
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@ -12,7 +12,9 @@ typedef enum {
tPath,
tNull,
tAttrs,
tList,
tList1,
tList2,
tListN,
tThunk,
tApp,
tLambda,
@ -119,9 +121,10 @@ struct Value
const char * path;
Bindings * attrs;
struct {
unsigned int length;
unsigned int size;
Value * * elems;
} list;
} bigList;
Value * smallList[2];
struct {
Env * env;
Expr * expr;
@ -139,6 +142,26 @@ struct Value
} primOpApp;
ExternalValueBase * external;
};
bool isList() const
{
return type == tList1 || type == tList2 || type == tListN;
}
Value * * listElems()
{
return type == tList1 || type == tList2 ? smallList : bigList.elems;
}
const Value * const * listElems() const
{
return type == tList1 || type == tList2 ? smallList : bigList.elems;
}
unsigned int listSize() const
{
return type == tList1 ? 1 : type == tList2 ? 2 : bigList.size;
}
};