Revert "Implement noAllocationValue for Expr's and use it to avoid so…

…me allocs"

This reverts commit 4a2c47a.

src/libexpr/eval.cc

@@ -826,21 +826,15 @@ void EvalState::mkPos(Value & v, Pos * pos)
         mkNull(v);
 }
 
-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 * Expr::maybeThunk(EvalState & state, Env & env)
 {
-    Value * v = noAllocationValue(state, env);
-    if (!v) {
-        v = state.allocValue();
-        mkThunk(*v, env, this);
-    } else {
-        nrAvoided++;
-    }
+    Value * v = state.allocValue();
+    mkThunk(*v, env, this);
     return v;
 }
 
@@ -849,35 +843,39 @@ void Expr::evalWithStrategy(EvalState & state, Env & env, Value & v, EvalStrateg
     abort();
 }
 
-Value * Expr::noAllocationValue(EvalState & state, Env & env)
-{
-    return nullptr;
-}
+unsigned long nrAvoided = 0;
 
-Value * ExprVar::noAllocationValue(EvalState & state, Env & env)
+Value * ExprVar::maybeThunk(EvalState & state, Env & env)
 {
+    Value * v = state.lookupVar(&env, *this, true);
     /* The value might not be initialised in the environment yet.
        In that case, ignore it. */
-    return state.lookupVar(&env, *this, true);
+    if (v) { nrAvoided++; return v; }
+    return Expr::maybeThunk(state, env);
 }
 
-Value * ExprString::noAllocationValue(EvalState & state, Env & env)
+
+Value * ExprString::maybeThunk(EvalState & state, Env & env)
 {
+    nrAvoided++;
     return &v;
 }
 
-Value * ExprInt::noAllocationValue(EvalState & state, Env & env)
+Value * ExprInt::maybeThunk(EvalState & state, Env & env)
 {
+    nrAvoided++;
     return &v;
 }
 
-Value * ExprFloat::noAllocationValue(EvalState & state, Env & env)
+Value * ExprFloat::maybeThunk(EvalState & state, Env & env)
 {
+    nrAvoided++;
     return &v;
 }
 
-Value * ExprPath::noAllocationValue(EvalState & state, Env & env)
+Value * ExprPath::maybeThunk(EvalState & state, Env & env)
 {
+    nrAvoided++;
     return &v;
 }
 

src/libexpr/nixexpr.hh

@@ -99,8 +99,6 @@ struct Expr
 
 
     virtual Value * maybeThunk(EvalState & state, Env & env);
-    // Return a Value if it can be obtained without doing any allocations
-    virtual Value * noAllocationValue(EvalState & state, Env & env);
     virtual void setName(Symbol & name);
     virtual Pos getPos() { return noPos; };
 };
@@ -118,7 +116,7 @@ struct ExprInt : Expr
     Value v;
     ExprInt(NixInt n) : n(n) { mkInt(v, n); };
     COMMON_METHODS
-    Value * noAllocationValue(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env);
 };
 
 struct ExprFloat : Expr
@@ -127,7 +125,7 @@ struct ExprFloat : Expr
     Value v;
     ExprFloat(NixFloat nf) : nf(nf) { mkFloat(v, nf); };
     COMMON_METHODS
-    Value * noAllocationValue(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env);
 };
 
 struct ExprString : Expr
@@ -136,7 +134,7 @@ struct ExprString : Expr
     Value v;
     ExprString(const Symbol & s) : s(s) { mkString(v, s); };
     COMMON_METHODS
-    Value * noAllocationValue(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env);
 };
 
 /* Temporary class used during parsing of indented strings. */
@@ -152,7 +150,7 @@ struct ExprPath : Expr
     Value v;
     ExprPath(const string & s) : s(s) { mkPathNoCopy(v, this->s.c_str()); };
     COMMON_METHODS
-    Value * noAllocationValue(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env);
 };
 
 struct ExprVar : Expr
@@ -176,7 +174,7 @@ struct ExprVar : Expr
     ExprVar(const Symbol & name) : name(name) { };
     ExprVar(const Pos & pos, const Symbol & name) : pos(pos), name(name) { };
     COMMON_METHODS
-    Value * noAllocationValue(EvalState & state, Env & env);
+    Value * maybeThunk(EvalState & state, Env & env);
     Pos getPos() { return pos; };
 };