fix expander: optimize lazily

Author: bksaiki

src/eval.c

@@ -860,7 +860,7 @@ obj eval_expr(obj e) {
     obj tc, k, env, v, ab;
     uptr aa, ac;
 
-    // check and expand
+    // check and expand expression
     check_expr(e);
     e = expand_expr(e);
 
@@ -892,16 +892,25 @@ obj eval_expr(obj e) {
 }
 
 void eval_module(obj mod) {
-    obj tc, k, env;
+    obj tc, k, env, ab;
+    uptr aa, ac;
 
-    // stash old continuation and environment
+    // check and expand module
+    check_module(mod);
+    expand_module(mod);
+
+    // stash mutable thread context info
     tc = Mcurr_tc();
     k = Mtc_cc(tc);
     env = Mtc_env(tc);
-
-    // check module syntax
-    check_module(mod);
-    expand_module(mod);
+    ab = Mtc_ab(tc);
+    aa = Mtc_aa(tc);
+    ac = Mtc_ac(tc);
+    
+    // create new argument buffer
+    Mtc_aa(tc) = INIT_ARGS_BUFFER_LEN;
+    Mtc_ab(tc) = GC_malloc(Mtc_aa(tc) * sizeof(obj));
+    Mtc_ac(tc) = 0;
 
     // set up thread context
     Mtc_env(tc) = empty_env();
@@ -913,7 +922,10 @@ void eval_module(obj mod) {
     do_module_body(mod);
     do_exports(tc, mod);
 
-    // restore old continuation and environment
+    // restore mutable thread context info
     Mtc_cc(tc) = k;
     Mtc_env(tc) = env;
+    Mtc_ab(tc) = ab;
+    Mtc_aa(tc) = aa;
+    Mtc_ac(tc) = ac;
 }

src/expand.c

@@ -5,10 +5,10 @@
 static obj condense_body(obj es) {
     if (Mnullp(Mcdr(es))) {
         // single expression => just use expression
-        return expand_expr(Mcar(es));
+        return Mcar(es);
     } else {
         // multiple expressions => wrap in begin
-        return expand_expr(Mcons(Mbegin_symbol, es));
+        return Mcons(Mbegin_symbol, es);
     }
 }
 
@@ -46,7 +46,7 @@ static obj expand_let_values_expr(obj e) {
         tl = Mcdr(tl);
     }
 
-    return Mlist3(Mlet_values_symbol, hd, condense_body(Mcddr(e)));
+    return Mlist3(Mlet_values_symbol, hd, expand_expr(condense_body(Mcddr(e))));
 }
 
 // ([(<id> ...) <expr>] ...)
@@ -265,29 +265,31 @@ obj expand_expr(obj e) {
             if (Msymbolp(Mcadr(e))) {
                 // named let => convert to letrec
                 e = expand_let_loop(e);
-                goto loop;
             } else if (Mnullp(Mcadr(e))) {
                 // empty bindings => just use body
-                return condense_body(Mcddr(e));
+                e = condense_body(Mcddr(e));
             } else {
                 // at least one binding
-                e = expand_let_expr(e);
-                goto loop;
+                e = expand_let_expr(e);   
             }
+
+            goto loop;
         } else if (hd == Mletrec_symbol) {
             // letrec => transforms to let
             if (Mnullp(Mcadr(e))) {
                 // empty bindings => just use body
-                return condense_body(Mcddr(e));
+                e = condense_body(Mcddr(e));
             } else {
                 // at least one binding
                 e = expand_letrec_expr(e);
-                goto loop;
             }
+
+            goto loop;
         } else if (hd == Mlet_values_symbol) {
             if (Mnullp(Mcadr(e))) {
                 // empty bindings => just use body
-                return condense_body(Mcddr(e));
+                e = condense_body(Mcddr(e));
+                goto loop;
             } else {
                 // at least one binding
                 return expand_let_values_expr(e);
@@ -327,19 +329,11 @@ obj expand_expr(obj e) {
                 expand_expr(Mcar(Mcdddr(e)))
             );
         } else if (hd == Mwhen_symbol) {
-            return Mlist4(
-                Mif_symbol,
-                expand_expr(Mcadr(e)),
-                expand_expr(Mcons(Mbegin_symbol, Mcddr(e))),
-                Mlist2(Mquote_symbol, Mvoid)
-            );
+            e = Mlist4(Mif_symbol, Mcadr(e), Mcons(Mbegin_symbol, Mcddr(e)), Mlist2(Mquote_symbol, Mvoid));
+            goto loop;
         } else if (hd == Munless_symbol) {
-            return Mlist4(
-                Mif_symbol,
-                expand_expr(Mcadr(e)),
-                Mlist2(Mquote_symbol, Mvoid),
-                expand_expr(Mcons(Mbegin_symbol, Mcddr(e)))
-            );
+            e = Mlist4(Mif_symbol, Mcadr(e), Mlist2(Mquote_symbol, Mvoid), Mcons(Mbegin_symbol, Mcddr(e)));
+            goto loop;
         } else if (hd == Mcond_symbol) {
             if (Mnullp(Mcdr(e))) {
                 // empty cond => void
@@ -374,7 +368,7 @@ obj expand_expr(obj e) {
                 goto loop;
             }
         } else if (hd == Mlambda_symbol) {
-            return Mlist3(Mlambda_symbol, Mcadr(e), condense_body(Mcddr(e)));
+            return Mlist3(Mlambda_symbol, Mcadr(e), expand_expr(condense_body(Mcddr(e))));
         } else if (hd == Msetb_symbol) {
             return Mlist3(Msetb_symbol, Mcadr(e), expand_expr(Mcaddr(e)));
         } else if (hd == Mquote_symbol) {