Add a new instruction `OP_LOADI16`.

Which loads 16bit integer to the register. The instruction number should
be reorder on massive instruction refactoring. The instruction is added
for `mruby/c` which had performance issue with `OP_EXT`. With this
instruction, `mruby/c` VM can just raise errors on `OP_EXT` extension
instructions.

include/mruby/ops.h

@@ -115,3 +115,4 @@ OPCODE(EXT1,       Z)        /* make 1st operand 16bit */
 OPCODE(EXT2,       Z)        /* make 2nd operand 16bit */
 OPCODE(EXT3,       Z)        /* make 1st and 2nd operands 16bit */
 OPCODE(STOP,       Z)        /* stop VM */
+OPCODE(LOADI16,    BS)       /* R(a) = mrb_int(b) */

mrbgems/mruby-compiler/core/codegen.c

@@ -2440,12 +2440,20 @@ codegen(codegen_scope *s, node *tree, int val)
       else
 #endif
       {
-        if (i == -1) genop_1(s, OP_LOADI__1, cursp());
-        else if (i < 0) genop_2(s, OP_LOADINEG, cursp(), (uint16_t)-i);
+        if (i < 0) {
+          if (i == -1) genop_1(s, OP_LOADI__1, cursp());
+          else if (i >= -0xff) genop_2(s, OP_LOADINEG, cursp(), (uint16_t)-i); 
+          else if (i >= -0x8000) genop_2S(s, OP_LOADI16, cursp(), (uint16_t)i);
+          else goto lit_int;
+        }
         else if (i < 8) genop_1(s, OP_LOADI_0 + (uint8_t)i, cursp());
-        else if (i <= 0xffff) genop_2(s, OP_LOADI, cursp(), (uint16_t)i);
+        else if (i <= 0xff) genop_2(s, OP_LOADI, cursp(), (uint16_t)i);
+        else if (i <= 0xffff) genop_2S(s, OP_LOADI16, cursp(), (uint16_t)i);
         else {
-          int off = new_lit(s, mrb_fixnum_value(i));
+          int off;
+
+        lit_int:
+          off = new_lit(s, mrb_fixnum_value(i));
           genop_2(s, OP_LOADL, cursp(), off);
         }
       }
@@ -2501,9 +2509,12 @@ codegen(codegen_scope *s, node *tree, int val)
           else {
 #endif
             if (i == -1) genop_1(s, OP_LOADI__1, cursp());
-            else if (i >= -0xffff) {
+            else if (i >= -0xff) {
               genop_2(s, OP_LOADINEG, cursp(), (uint16_t)-i);
             }
+            else if (i >= -0x8000) {
+              genop_2S(s, OP_LOADI16, cursp(), (uint16_t)i);
+            }
             else {
               int off = new_lit(s, mrb_fixnum_value(i));
               genop_2(s, OP_LOADL, cursp(), off);

src/codedump.c

@@ -130,6 +130,10 @@ codedump(mrb_state *mrb, mrb_irep *irep)
       printf("OP_LOADI\tR%d\t-%d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
+    CASE(OP_LOADI16, BS):
+      printf("OP_LOADI16\tR%d\t%d\t", a, (int)(int16_t)b);
+      print_lv_a(mrb, irep, a);
+      break;
     CASE(OP_LOADI__1, B):
       printf("OP_LOADI__1\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);

src/vm.c

@@ -1047,6 +1047,11 @@ RETRY_TRY_BLOCK:
       NEXT;
     }
 
+    CASE(OP_LOADI16, BS) {
+      SET_INT_VALUE(regs[a], (mrb_int)(int16_t)b);
+      NEXT;
+    }
+
     CASE(OP_LOADSYM, BB) {
       SET_SYM_VALUE(regs[a], syms[b]);
       NEXT;