Introduced instructions to engage with a call stack

Essentially you may "call" an absolute program address, which pushes
the current address onto the call stack.  CALL_STACK does the same
thing but the absolute program address is taken from the data stack.
RET pops an address off the call stack then jumps to that address.

2 files changed, 23 insertions, 8 deletions

diff --git a/lib/inst.c b/lib/inst.c
index da951fe..30612d8 100644
--- a/lib/inst.c
+++ b/lib/inst.c
@@ -199,6 +199,12 @@ const char *opcode_as_cstr(opcode_t code)
     return "JUMP_IF_HWORD";
   case OP_JUMP_IF_WORD:
     return "JUMP_IF_WORD";
+  case OP_CALL:
+    return "CALL";
+  case OP_CALL_STACK:
+    return "CALL_STACK";
+  case OP_RET:
+    return "RET";
   case OP_PRINT_CHAR:
     return "PRINT_CHAR";
   case OP_PRINT_BYTE:
@@ -239,7 +245,7 @@ void data_print(data_t datum, data_type_t type, FILE *fp)
 
 void inst_print(inst_t instruction, FILE *fp)
 {
-  static_assert(NUMBER_OF_OPCODES == 95, "inst_bytecode_size: Out of date");
+  static_assert(NUMBER_OF_OPCODES == 98, "inst_bytecode_size: Out of date");
   fprintf(fp, "%s(", opcode_as_cstr(instruction.opcode));
   if (OPCODE_IS_TYPE(instruction.opcode, OP_PUSH))
   {
@@ -261,7 +267,8 @@ void inst_print(inst_t instruction, FILE *fp)
     fprintf(fp, "n=%lu", instruction.operand.as_word);
   }
   else if (instruction.opcode == OP_JUMP_ABS ||
-           OPCODE_IS_TYPE(instruction.opcode, OP_JUMP_IF))
+           OPCODE_IS_TYPE(instruction.opcode, OP_JUMP_IF) ||
+           instruction.opcode == OP_CALL)
   {
     fprintf(fp, "address=0x");
     data_print(instruction.operand, DATA_TYPE_WORD, fp);
@@ -271,7 +278,7 @@ void inst_print(inst_t instruction, FILE *fp)
 
 size_t inst_bytecode_size(inst_t inst)
 {
-  static_assert(NUMBER_OF_OPCODES == 95, "inst_bytecode_size: Out of date");
+  static_assert(NUMBER_OF_OPCODES == 98, "inst_bytecode_size: Out of date");
   size_t size = 1; // for opcode
   if (OPCODE_IS_TYPE(inst.opcode, OP_PUSH))
   {
@@ -288,14 +295,14 @@ size_t inst_bytecode_size(inst_t inst)
            OPCODE_IS_TYPE(inst.opcode, OP_MALLOC) ||
            OPCODE_IS_TYPE(inst.opcode, OP_MSET) ||
            OPCODE_IS_TYPE(inst.opcode, OP_MGET) || inst.opcode == OP_JUMP_ABS ||
-           OPCODE_IS_TYPE(inst.opcode, OP_JUMP_IF))
+           OPCODE_IS_TYPE(inst.opcode, OP_JUMP_IF) || inst.opcode == OP_CALL)
     size += WORD_SIZE;
   return size;
 }
 
 void inst_write_bytecode(inst_t inst, darr_t *darr)
 {
-  static_assert(NUMBER_OF_OPCODES == 95, "inst_write_bytecode: Out of date");
+  static_assert(NUMBER_OF_OPCODES == 98, "inst_write_bytecode: Out of date");
   // Append opcode
   darr_append_byte(darr, inst.opcode);
   // Then append 0 or more operands
@@ -308,7 +315,7 @@ void inst_write_bytecode(inst_t inst, darr_t *darr)
            OPCODE_IS_TYPE(inst.opcode, OP_MALLOC) ||
            OPCODE_IS_TYPE(inst.opcode, OP_MSET) ||
            OPCODE_IS_TYPE(inst.opcode, OP_MGET) || inst.opcode == OP_JUMP_ABS ||
-           OPCODE_IS_TYPE(inst.opcode, OP_JUMP_IF))
+           OPCODE_IS_TYPE(inst.opcode, OP_JUMP_IF) || inst.opcode == OP_CALL)
     to_append = DATA_TYPE_WORD;
 
   switch (to_append)
@@ -370,7 +377,7 @@ data_t read_type_from_darr(darr_t *darr, data_type_t type)
 
 inst_t inst_read_bytecode(darr_t *darr)
 {
-  static_assert(NUMBER_OF_OPCODES == 95, "inst_read_bytecode: Out of date");
+  static_assert(NUMBER_OF_OPCODES == 98, "inst_read_bytecode: Out of date");
   if (darr->used >= darr->available)
     return (inst_t){0};
   inst_t inst     = {0};
@@ -385,7 +392,8 @@ inst_t inst_read_bytecode(darr_t *darr)
            OPCODE_IS_TYPE(opcode, OP_MOV) || OPCODE_IS_TYPE(opcode, OP_DUP) ||
            OPCODE_IS_TYPE(opcode, OP_MALLOC) ||
            OPCODE_IS_TYPE(opcode, OP_MSET) || OPCODE_IS_TYPE(opcode, OP_MGET) ||
-           opcode == OP_JUMP_ABS || OPCODE_IS_TYPE(opcode, OP_JUMP_IF))
+           opcode == OP_JUMP_ABS || OPCODE_IS_TYPE(opcode, OP_JUMP_IF) ||
+           opcode == OP_CALL)
     inst.operand = read_type_from_darr(darr, DATA_TYPE_WORD);
   // Otherwise opcode doesn't take operands
 
diff --git a/lib/inst.h b/lib/inst.h
index 55c062f..3877a2b 100644
--- a/lib/inst.h
+++ b/lib/inst.h
@@ -148,6 +148,10 @@ typedef enum
   OP_JUMP_IF_BYTE,
   OP_JUMP_IF_HWORD,
   OP_JUMP_IF_WORD,
+  // Subroutines
+  OP_CALL,
+  OP_CALL_STACK,
+  OP_RET,
 
   // Should not be an opcode
   NUMBER_OF_OPCODES,
@@ -231,6 +235,9 @@ inst_t *insts_read_bytecode_file(FILE *, size_t *);
 #define INST_JUMP_STACK ((inst_t){.opcode = OP_JUMP_STACK})
 #define INST_JUMP_IF(TYPE, OP) \
   ((inst_t){.opcode = OP_JUMP_IF_##TYPE, .operand = DWORD(OP)})
+#define INST_CALL(OP)   ((inst_t){.opcode = OP_CALL, .operand = DWORD(OP)})
+#define INST_CALL_STACK ((inst_t){.opcode = OP_CALL_STACK})
+#define INST_RET        ((inst_t){.opcode = OP_RET})
 
 #define INST_PRINT(TYPE) ((inst_t){.opcode = OP_PRINT_##TYPE})
 #endif