Improve construction of local environments and stores

runtime/src/main/java/dev/ionfusion/fusion/LambdaForm.java

@@ -41,14 +41,11 @@ SyntaxValue<?> expand(Expander expander, Environment env, SyntaxSexp stx)
         var formals = children[1];
         var args = flattenFormals(eval, check, formals);
 
-        // When there's no args, we can avoid an empty binding rib at runtime.
-        // TODO #67 This will need changing for internal definitions
-        //      since we won't know yet whether the rib will be empty or not.
         LocalEnvironment localEnv = null;
         if (args.length != 0)
         {
             ensureUniqueIdentifiers(eval, args, stx);
-            env = localEnv = new LocalEnvironment(env, args);
+            env = localEnv = LocalEnvironment.forExpansion(env, args);
         }
 
         // Prepare the bound names so they resolve to their own binding.
@@ -149,11 +146,8 @@ CompiledForm compile(Compiler comp, Environment env, SyntaxSexp stx)
 
         var formalsDecl = stx.get(eval, 1);
         var formals = flattenFormals(eval, formalsDecl);
-        if (formals.length != 0)
-        {
-            // We micro-optimize by avoiding an environment frame for no-arg procedures.
-            env = LocalEnvironment.forBinders(env, formals);
-        }
+
+        env = LocalEnvironment.forCompilation(env, formals);
 
         CompiledForm body = comp.compileBegin(env, stx, 2);
 
@@ -414,8 +408,7 @@ Object doApply(Evaluator eval, Object[] args)
         {
             checkArityExact(eval, myArity, args);
 
-            Store localStore = new LocalStore(myEnclosure, args);
-
+            Store localStore = LocalStore.forExecution(myEnclosure, args);
             return eval.bounceTailForm(localStore, myBody);
         }
     }

runtime/src/main/java/dev/ionfusion/fusion/LetValuesForm.java

@@ -68,7 +68,7 @@ SyntaxValue expand(Expander expander, Environment env, SyntaxSexp stx)
         {
             boundNames = boundNameList.toArray(SyntaxSymbol.EMPTY_ARRAY);
             ensureUniqueIdentifiers(eval, boundNames, stx);
-            var localEnv = new LocalEnvironment(env, boundNames);
+            var localEnv = LocalEnvironment.forExpansion(env, boundNames);
             localWrap = localEnv.getWrap();
             bodyEnv   = localEnv;
         }
@@ -171,11 +171,7 @@ CompiledForm compile(Compiler comp, Environment env, SyntaxSexp expr)
             valuePosns[i] = boundExpr.getPosition();
         }
 
-        if (bindingCount != 0)
-        {
-            // Dummy environment to keep track of depth
-            env = LocalEnvironment.forBinders(env, binders.toArray(new SyntaxSymbol[0]));
-        }
+        env = LocalEnvironment.forCompilation(env, binders.toArray(new SyntaxSymbol[0]));
 
         CompiledForm body = comp.compileBegin(env, expr, 2);
 
@@ -249,7 +245,7 @@ public Object doEval(Evaluator eval, Store store)
                 boundValues[i] = values;
             }
 
-            Store localStore = new LocalStore(store, boundValues);
+            Store localStore = LocalStore.forExecution(store, boundValues);
             return eval.bounceTailForm(localStore, myBody);
         }
     }
@@ -393,7 +389,7 @@ else if (values instanceof Object[])
                 }
             }
 
-            Store localStore = LocalStore.forLocals(store, boundValues);
+            Store localStore = LocalStore.forExecution(store, boundValues);
             return eval.bounceTailForm(localStore, myBody);
         }
     }

runtime/src/main/java/dev/ionfusion/fusion/LetrecForm.java

@@ -37,7 +37,7 @@ SyntaxValue expand(Expander expander, Environment env, SyntaxSexp stx)
         }
         ensureUniqueIdentifiers(eval, boundNames, stx);
 
-        var bodyEnv = new LocalEnvironment(env, boundNames);
+        var bodyEnv = LocalEnvironment.forExpansion(env, boundNames);
         SyntaxWrap localWrap = bodyEnv.getWrap();
 
         // Expand the bound-value expressions
@@ -107,10 +107,7 @@ CompiledForm compile(Compiler comp, Environment env, SyntaxSexp stx)
 
         var bindingForms = (SyntaxSequence) stx.get(eval, 1);
         var binders = collectBinders(eval, bindingForms);
-        if (binders.length != 0)
-        {
-            env = LocalEnvironment.forBinders(env, binders);
-        }
+        env = LocalEnvironment.forCompilation(env, binders);
 
         final int numBindings = binders.length;
         CompiledForm    [] valueForms = new CompiledForm    [numBindings];
@@ -168,7 +165,7 @@ public Object doEval(Evaluator eval, Store store)
             Object[] boundValues = new Object[numBindings];
             Arrays.fill(boundValues, UNDEF);
 
-            Store localStore = new LocalStore(store, boundValues);
+            Store localStore = LocalStore.forExecution(store, boundValues);
 
             for (int i = 0; i < numBindings; i++)
             {

runtime/src/main/java/dev/ionfusion/fusion/LocalEnvironment.java

@@ -130,61 +130,64 @@ Binding resolveMaybe(BaseSymbol name,
 
     /** Not null */
     private final Environment    myEnclosure;
-    private final Namespace      myNamespace;
     private final LocalBinding[] myBindings;
     private final SyntaxWrap     myWrap;
 
 
-    /**
-     * Expand-time environment construction.
-     */
-    LocalEnvironment(Environment enclosure, SyntaxSymbol[] identifiers)
+    private LocalEnvironment(Environment enclosure,
+                             LocalBinding[] bindings,
+                             boolean makeWrap)
     {
         myEnclosure = enclosure;
-        myNamespace = enclosure.namespace();
+        myBindings = bindings;
+        myWrap = makeWrap ? new LocalEnvironmentWrap() : null;
+    }
 
+
+    /**
+     * Expand-time environment construction creates bindings for each identifier.
+     */
+    static LocalEnvironment forExpansion(Environment enclosure,
+                                         SyntaxSymbol[] identifiers)
+    {
         // 2019-04 Stats from the standard library and test suite:
         //   85% of local envs have 1 entry, 12% have 2.
         //   99% have 3 or fewer entries and none have more than 5.
         int count = identifiers.length;
-        myBindings = new LocalBinding[count];
+        var bindings = new LocalBinding[count];
         for (int i = 0; i < count; i++)
         {
             SyntaxSymbol identifier = identifiers[i];
-            myBindings[i] = new LocalBinding(identifier);
+            bindings[i] = new LocalBinding(identifier);
         }
 
-        myWrap = new LocalEnvironmentWrap();
+        return new LocalEnvironment(enclosure, bindings, true);
     }
 
 
     /**
-     * Compile-time environment does not create bindings but uses them to
-     * determine access coordinates.
+     * Compile-time environment does not create bindings but uses them to determine
+     * variable addresses.
+     * <p>
+     * Logic for empty layers must mirror {@link LocalStore#forExecution}.
      */
-    private LocalEnvironment(Environment enclosure, LocalBinding[] bindings)
+    static Environment forCompilation(Environment enclosure, SyntaxSymbol[] binders)
     {
-        myEnclosure = enclosure;
-        myNamespace = enclosure.namespace();
-        myBindings = bindings;
-        myWrap = null;
-    }
+        if (binders.length == 0) return enclosure;
 
-    static LocalEnvironment forBinders(Environment enclosure, SyntaxSymbol[] binders)
-    {
         LocalBinding[] bindings = new LocalBinding[binders.length];
         for (int i = 0; i < binders.length; i++)
         {
             bindings[i] = (LocalBinding) binders[i].resolve();
         }
-        return new LocalEnvironment(enclosure, bindings);
+        return new LocalEnvironment(enclosure, bindings, false);
     }
 
 
     @Override
     public Namespace namespace()
     {
-        return myNamespace;
+        return myEnclosure.namespace();
     }
 
     public SyntaxWrap getWrap()

runtime/src/main/java/dev/ionfusion/fusion/LocalStore.java

@@ -18,7 +18,7 @@ final class LocalStore
      * Caller can (and does) mutate the array elements after constructing the
      * store!
      */
-    LocalStore(Store enclosure, Object[] values)
+    private LocalStore(Store enclosure, Object[] values)
     {
         assert values.length > 0;
         myEnclosure = enclosure;
@@ -68,9 +68,15 @@ public void set(int rib, int address, Object value)
     //==================================================================================
     // Factories
 
-    public static Store forLocals(Store enclosure, Object[] locals)
+
+    /**
+     * Logic for empty layers must mirror {@link LocalEnvironment#forCompilation}.
+     *
+     * @param values THE STORE ASSUMES OWNERSHIP OF THIS ARRAY.
+     */
+    public static Store forExecution(Store enclosure, Object[] values)
     {
-        if (locals.length == 0) return enclosure;
-        return new LocalStore(enclosure, locals);
+        if (values.length == 0) return enclosure;
+        return new LocalStore(enclosure, values);
     }
 }