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libexpr: don't inline small lists into values

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this has no measurable performance impact thanks to the new caches.

Change-Id: Ib403a9a567161675f78e8c5d314d6340183d181d
This commit is contained in:
eldritch horrors
2025-09-28 00:02:20 +02:00
parent b36a19e50c
commit d37a5d4000
4 changed files with 42 additions and 75 deletions
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lix/libexpr/eval.cc
+1 -3
View File
@@ -858,9 +858,7 @@ Value EvalMemory::newList(size_t size)
{
Value v;
v.mkList(size);
if (size > 2) {
v._bigList.elems = allocType<Value *>(size);
}
v._list.elems = allocType<Value *>(size);
stats.nrListElems += size;
return v;
}
lix/libexpr/value.hh
+19 -50
View File
@@ -20,7 +20,6 @@ namespace nix {
class BindingsBuilder;
typedef enum {
tInt = 1,
tBool,
@@ -28,9 +27,7 @@ typedef enum {
tPath,
tNull,
tAttrs,
tList1,
tList2,
tListN,
tList,
tThunk,
tApp,
tLambda,
@@ -378,19 +375,9 @@ public:
/// allocating memory.
Value(list_t, std::span<Value *> items)
{
if (items.size() == 1) {
this->internalType = tList1;
this->_smallList[0] = items[0];
this->_smallList[1] = nullptr;
} else if (items.size() == 2) {
this->internalType = tList2;
this->_smallList[0] = items[0];
this->_smallList[1] = items[1];
} else {
this->internalType = tListN;
this->_bigList.size = items.size();
this->_bigList.elems = items.data();
}
this->internalType = tList;
this->_list.size = items.size();
this->_list.elems = items.data();
}
/// Constructs a nix language value of type "list", with an element array
@@ -406,24 +393,12 @@ public:
>
Value(list_t, SizedIterableT & items, TransformerT const & transformer)
{
if (items.size() == 1) {
this->internalType = tList1;
this->_smallList[0] = transformer(*items.begin());
this->_smallList[1] = nullptr;
} else if (items.size() == 2) {
this->internalType = tList2;
auto it = items.begin();
this->_smallList[0] = transformer(*it);
it++;
this->_smallList[1] = transformer(*it);
} else {
this->internalType = tListN;
this->_bigList.size = items.size();
this->_bigList.elems = gcAllocType<Value *>(items.size());
auto it = items.begin();
for (size_t i = 0; i < items.size(); i++, it++) {
this->_bigList.elems[i] = transformer(*it);
}
this->internalType = tList;
this->_list.size = items.size();
this->_list.elems = gcAllocType<Value *>(items.size());
auto it = items.begin();
for (size_t i = 0; i < items.size(); i++, it++) {
this->_list.elems[i] = transformer(*it);
}
}
@@ -594,8 +569,7 @@ public:
struct {
size_t size;
Value * * elems;
} _bigList;
Value * _smallList[2];
} _list;
struct {
Env * env;
Expr * expr;
@@ -640,7 +614,8 @@ public:
case tPath: return nPath;
case tNull: return nNull;
case tAttrs: return nAttrs;
case tList1: case tList2: case tListN: return nList;
case tList:
return nList;
case tLambda: case tPrimOp: case tPrimOpApp: return nFunction;
case tExternal: return nExternal;
case tFloat: return nFloat;
@@ -720,14 +695,8 @@ public:
inline void mkList(size_t size)
{
clearValue();
if (size == 1)
internalType = tList1;
else if (size == 2)
internalType = tList2;
else {
internalType = tListN;
_bigList.size = size;
}
internalType = tList;
_list.size = size;
}
inline void mkThunk(Env * e, Expr & ex)
@@ -787,22 +756,22 @@ public:
bool isList() const
{
return internalType == tList1 || internalType == tList2 || internalType == tListN;
return internalType == tList;
}
Value * * listElems()
{
return internalType == tList1 || internalType == tList2 ? _smallList : _bigList.elems;
return _list.elems;
}
Value * const * listElems() const
{
return internalType == tList1 || internalType == tList2 ? _smallList : _bigList.elems;
return _list.elems;
}
size_t listSize() const
{
return internalType == tList1 ? 1 : internalType == tList2 ? 2 : _bigList.size;
return _list.size;
}
/**
tests/functional/lang/eval-okay-print.exp
+1 -1
View File
@@ -1 +1 @@
[ null <PRIMOP> <PRIMOP-APP> <LAMBDA> [ [ «repeated» ] ] ]
[ null <PRIMOP> <PRIMOP-APP> <LAMBDA> [ «repeated» ] ]
tests/unit/libexpr/value/print.cc
+21 -21
View File
@@ -83,9 +83,9 @@ TEST_F(ValuePrintingTests, tList)
vTwo.mkInt(2);
Value vList = evaluator.mem.newList(5);
vList._bigList.elems[0] = &vOne;
vList._bigList.elems[1] = &vTwo;
vList._bigList.size = 3;
vList._list.elems[0] = &vOne;
vList._list.elems[1] = &vTwo;
vList._list.size = 3;
test(vList, "[ 1 2 «nullptr» ]");
}
@@ -261,10 +261,10 @@ TEST_F(ValuePrintingTests, depthList)
vNested.mkAttrs(builder2.finish());
Value vList = evaluator.mem.newList(5);
vList._bigList.elems[0] = &vOne;
vList._bigList.elems[1] = &vTwo;
vList._bigList.elems[2] = &vNested;
vList._bigList.size = 3;
vList._list.elems[0] = &vOne;
vList._list.elems[1] = &vTwo;
vList._list.elems[2] = &vNested;
vList._list.size = 3;
test(vList, "[ 1 2 { ... } ]", PrintOptions { .maxDepth = 1 });
test(vList, "[ 1 2 { nested = { ... }; one = 1; two = 2; } ]", PrintOptions { .maxDepth = 2 });
@@ -534,9 +534,9 @@ TEST_F(ValuePrintingTests, ansiColorsList)
vTwo.mkInt(2);
Value vList = evaluator.mem.newList(5);
vList._bigList.elems[0] = &vOne;
vList._bigList.elems[1] = &vTwo;
vList._bigList.size = 3;
vList._list.elems[0] = &vOne;
vList._list.elems[1] = &vTwo;
vList._list.size = 3;
test(vList,
"[ " ANSI_CYAN "1" ANSI_NORMAL " " ANSI_CYAN "2" ANSI_NORMAL " " ANSI_MAGENTA "«nullptr»" ANSI_NORMAL " ]",
@@ -672,9 +672,9 @@ TEST_F(ValuePrintingTests, ansiColorsListRepeated)
vInner.mkAttrs(innerBuilder.finish());
Value vList = evaluator.mem.newList(3);
vList._bigList.elems[0] = &vInner;
vList._bigList.elems[1] = &vInner;
vList._bigList.size = 2;
vList._list.elems[0] = &vInner;
vList._list.elems[1] = &vInner;
vList._list.size = 2;
test(vList,
"[ { x = " ANSI_CYAN "0" ANSI_NORMAL "; } " ANSI_MAGENTA "«repeated»" ANSI_NORMAL " ]",
@@ -695,9 +695,9 @@ TEST_F(ValuePrintingTests, listRepeated)
vInner.mkAttrs(innerBuilder.finish());
Value vList = evaluator.mem.newList(3);
vList._bigList.elems[0] = &vInner;
vList._bigList.elems[1] = &vInner;
vList._bigList.size = 2;
vList._list.elems[0] = &vInner;
vList._list.elems[1] = &vInner;
vList._list.size = 2;
test(vList, "[ { x = 0; } «repeated» ]", PrintOptions { });
test(vList,
@@ -752,9 +752,9 @@ TEST_F(ValuePrintingTests, ansiColorsListElided)
vTwo.mkInt(2);
Value vList = evaluator.mem.newList(4);
vList._bigList.elems[0] = &vOne;
vList._bigList.elems[1] = &vTwo;
vList._bigList.size = 2;
vList._list.elems[0] = &vOne;
vList._list.elems[1] = &vTwo;
vList._list.size = 2;
test(vList,
"[ " ANSI_CYAN "1" ANSI_NORMAL " " ANSI_FAINT "«1 item elided»" ANSI_NORMAL " ]",
@@ -766,8 +766,8 @@ TEST_F(ValuePrintingTests, ansiColorsListElided)
Value vThree;
vThree.mkInt(3);
vList._bigList.elems[2] = &vThree;
vList._bigList.size = 3;
vList._list.elems[2] = &vThree;
vList._list.size = 3;
test(vList,
"[ " ANSI_CYAN "1" ANSI_NORMAL " " ANSI_FAINT "«2 items elided»" ANSI_NORMAL " ]",