libexpr: move lambdas to auxiliary storage

Change-Id: Ibe4885f17c0ba1634ed6dbca0a45f8bd4619d69b

lix/libexpr/eval-inline.hh

@@ -26,6 +26,15 @@ inline Value::Value(app_t, EvalMemory & mem, Value & lhs, std::span<Value *> arg
     }
 }
 
+inline Value::Value(lambda_t, EvalMemory & mem, Env & env, ExprLambda & lambda)
+    : internalType(tAuxiliary)
+    , _aux_pad(0)
+{
+    auto lp = mem.allocType<Lambda>();
+    *lp = Lambda{{Acb::tLambda}, &env, &lambda};
+    _auxiliary = lp;
+}
+
 [[gnu::always_inline]]
 void * EvalMemory::allocBytes(size_t size)
 {

lix/libexpr/eval.cc

@@ -108,6 +108,7 @@ std::string showType(const Value & v)
             return v.external()->showType();
         case Value::Acb::tFloat:
         case Value::Acb::tNull:
+        case Value::Acb::tLambda:
             return std::string(showType(v.type()));
         case Value::Acb::tPrimOp:
             return fmt("the built-in function '%s'", v.primOp()->name);
@@ -1415,7 +1416,7 @@ void ExprOpHasAttr::eval(EvalState & state, Env & env, Value & v)
 
 void ExprLambda::eval(EvalState & state, Env & env, Value & v)
 {
-    v.mkLambda(&env, this);
+    v = {NewValueAs::lambda, state.ctx.mem, env, *this};
 }
 
 namespace {

lix/libexpr/value.hh

@@ -77,7 +77,6 @@ typedef enum {
     tList,
     tThunk,
     tApp,
-    tLambda,
     tAuxiliary,
 } InternalType;
 
@@ -259,6 +258,7 @@ public:
     struct String;
     struct Acb;
     struct Null;
+    struct Lambda;
 
     static const Null NULL_ACB;
 
@@ -521,10 +521,7 @@ public:
     /// This takes the environment the lambda is closed over @ref env, and
     /// the lambda expression itself @ref lambda, which will not be evaluated
     /// until it is applied.
-    Value(lambda_t, Env & env, ExprLambda & lambda)
-        : internalType(tLambda)
-        , _lambda({ .env = &env, .fun = &lambda })
-    { }
+    Value(lambda_t, EvalMemory & mem, Env & env, ExprLambda & lambda);
 
     /// Constructs an evil thunk, whose evaluation represents infinite recursion.
     explicit Value(blackhole_t)
@@ -582,7 +579,10 @@ public:
     }
 
     // type() == nFunction
-    inline bool isLambda() const { return internalType == tLambda; };
+    inline bool isLambda() const
+    {
+        return internalType == tAuxiliary && _auxiliary->type == Acb::tLambda;
+    };
     inline bool isPrimOp() const
     {
         return internalType == tAuxiliary && _auxiliary->type == Acb::tPrimOp;
@@ -690,6 +690,7 @@ public:
             tFloat,
             tNull,
             tPrimOp,
+            tLambda,
         } type;
     };
     struct External : Acb
@@ -706,6 +707,11 @@ public:
     {
         explicit PrimOp(PrimOpDetails && p) : Acb{tPrimOp}, PrimOpDetails(std::move(p)) {}
     };
+    struct Lambda : Acb
+    {
+        Env * env;
+        ExprLambda * fun;
+    };
 
     union
     {
@@ -737,11 +743,6 @@ public:
             Expr * expr;
         } _thunk;
         App _app;
-        struct
-        {
-            Env * env;
-            ExprLambda * fun;
-        } _lambda;
         struct {
             const Acb * _auxiliary;
             uintptr_t _aux_pad;
@@ -765,8 +766,6 @@ public:
             case tAttrs: return nAttrs;
             case tList:
                 return nList;
-            case tLambda:
-                return nFunction;
             case tAuxiliary:
                 switch (_auxiliary->type) {
                 case Acb::tExternal:
@@ -776,6 +775,7 @@ public:
                 case Acb::tNull:
                     return nNull;
                 case Acb::tPrimOp:
+                case Acb::tLambda:
                     return nFunction;
                 }
             case tThunk:
@@ -868,13 +868,6 @@ public:
         *this = {NewValueAs::app, *l, *r};
     }
 
-    inline void mkLambda(Env * e, ExprLambda * f)
-    {
-        internalType = tLambda;
-        _lambda.env = e;
-        _lambda.fun = f;
-    }
-
     inline void mkBlackhole()
     {
         internalType = tThunk;
@@ -992,7 +985,8 @@ public:
 
     const auto & lambda() const
     {
-        return _lambda;
+        assert(internalType == tAuxiliary && _auxiliary->type == Acb::tLambda);
+        return *static_cast<const Lambda *>(_auxiliary);
     }
 
     const PrimOp * primOp() const

tests/unit/libexpr/value/print.cc

@@ -110,6 +110,7 @@ TEST_F(ValuePrintingTests, vApp)
 
 TEST_F(ValuePrintingTests, vLambda)
 {
+    EvalMemory mem;
     Env env {
         .up = nullptr,
         .values = { }
@@ -120,8 +121,7 @@ TEST_F(ValuePrintingTests, vLambda)
     ExprLambda eLambda(posIdx, std::make_unique<AttrsPattern>(), std::make_unique<ExprLiteral>(noPos, NewValueAs::integer, 0));
     eLambda.pattern->name = createSymbol("a");
 
-    Value vLambda;
-    vLambda.mkLambda(&env, &eLambda);
+    Value vLambda{NewValueAs::lambda, mem, env, eLambda};
 
     test(vLambda, "«lambda @ «none»:1:1»");
 
@@ -546,6 +546,7 @@ TEST_F(ValuePrintingTests, ansiColorsList)
 
 TEST_F(ValuePrintingTests, ansiColorsLambda)
 {
+    EvalMemory mem;
     Env env {
         .up = nullptr,
         .values = { }
@@ -556,8 +557,7 @@ TEST_F(ValuePrintingTests, ansiColorsLambda)
     ExprLambda eLambda(posIdx, std::make_unique<AttrsPattern>(), std::make_unique<ExprLiteral>(noPos, NewValueAs::integer, 0));
     eLambda.pattern->name = createSymbol("a");
 
-    Value vLambda;
-    vLambda.mkLambda(&env, &eLambda);
+    Value vLambda{NewValueAs::lambda, mem, env, eLambda};
 
     test(vLambda,
          ANSI_BLUE "«lambda @ «none»:1:1»" ANSI_NORMAL,