Reduce unnecessary symbol table entry

include/mruby/symbol.h

@@ -16,6 +16,7 @@ MRB_BEGIN_DECL
 
 typedef enum mrb_reserved_symbol {
   mrb_sym_null = 0, // NULL symbol
+
   mrb_sym_add = 1, // +
   mrb_sym_sub = 2, // -
   mrb_sym_mul = 3, // *
@@ -25,9 +26,15 @@ typedef enum mrb_reserved_symbol {
   mrb_sym_le = 7, // <=
   mrb_sym_gt = 8, // >
   mrb_sym_ge = 9, // >=
+
   mrb_sym_method_missing = 10, // method_missing
 } mrb_reserved_symbol;
 
+static inline mrb_bool
+mrb_symbol_constsym_send_p(mrb_sym sym) {
+  return mrb_sym_add <= sym && sym <= mrb_sym_ge;
+}
+
 MRB_END_DECL
 
 #endif  /* MRUBY_SYMBOL_H */

mrbgems/mruby-compiler/core/codegen.c

@@ -18,6 +18,7 @@
 #include <mruby/opcode.h>
 #include <mruby/re.h>
 #include <mruby/throw.h>
+#include <mruby/symbol.h>
 
 #ifndef MRB_CODEGEN_LEVEL_MAX
 #define MRB_CODEGEN_LEVEL_MAX 1024
@@ -982,8 +983,9 @@ gen_call(codegen_scope *s, node *tree, mrb_sym name, int sp, int val, int safe)
     gen_move(s, cursp(), recv, 1);
     skip = genjmp2(s, OP_JMPNIL, cursp(), 0, val);
   }
-  // TODO: don't new when unused
-  idx = new_sym(s, sym);
+  if (!mrb_symbol_constsym_send_p(sym)) {
+    idx = new_sym(s, sym);
+  }
   tree = tree->cdr->cdr->car;
   if (tree) {
     n = gen_values(s, tree->car, VAL, sp?1:0);
@@ -2024,7 +2026,9 @@ codegen(codegen_scope *s, node *tree, int val)
       push(); pop();
       pop(); pop();
 
-      idx = new_sym(s, sym);
+      if (!mrb_symbol_constsym_send_p(sym)) {
+        idx = new_sym(s, sym);
+      }
       if (len == 1 && name[0] == '+')  {
         gen_addsub(s, OP_ADD, cursp());
       }