add 'call', 'callr', and 'ret' instrs

Author: vytdev

impl.h

@@ -362,4 +362,33 @@ DEF(wr64) {
   vmnext;
 }
 
+DEF(call) {
+  rvm_reg_t s_top = reg[RVM_RSP] -= 8;
+  util_checkaccs(s_top, 8);
+  RVM_ENC64(pc << 2, &mem[s_top]);
+  /* jump to addr */
+  pc += imm23s;
+  util_checkpc();
+  vmnext;
+}
+
+DEF(callr) {
+  rvm_reg_t s_top = reg[RVM_RSP] -= 8;
+  util_checkaccs(s_top, 8);
+  RVM_ENC64(pc << 2, &mem[s_top]);
+  /* jump to addr in reg */
+  pc += rgA >> 2;
+  util_checkpc();
+  vmnext;
+}
+
+DEF(ret) {
+  rvm_reg_t s_top = reg[RVM_RSP];
+  util_checkaccs(s_top, 8);
+  pc = RVM_DEC64(&mem[s_top]) >> 2;
+  reg[RVM_RSP] += 8;   /* dealloc 8 bytes from stack */
+  util_checkpc();
+  vmnext;
+}
+
 #endif /* impl.h */

opcodes.h

@@ -75,5 +75,8 @@ DEF(rd32,   53)   /* [I] 4B: rgA = mem[rgB + imm15s] */
 DEF(wr32,   54)   /* [I] 4B: mem[rgB + imm15s] = rgA */
 DEF(rd64,   55)   /* [I] 8B: rgA = mem[rgB + imm15s] */
 DEF(wr64,   56)   /* [I] 8B: mem[rgB + imm15s] = rgA */
+DEF(call,   57)   /* [J] call a subroutine */
+DEF(callr,  58)   /* [M] call a subroutine from reg addr */
+DEF(ret,    59)   /* [J] return to caller */
 
 #endif /* opcodes.h */

test/naive_fib_40

@@ -0,0 +1,22 @@
+10005003:    li r1, #40
+00000239:    call fib
+00000002:    trap #0x0
+
+             fib:
+10000206:    cmpi r1, #1
+0000042a:    ja _eval
+01000001:    mov r0, r1
+0000003b:    ret
+             _eval:
+ff00080a:    subi sp, sp, #4
+2f000036:    wr32 r2, #0(sp)
+10000022:    dec r1
+fffff039:    call fib
+20000001:    mov r2, r0
+10000022:    dec r1
+ffffea39:    call fib
+00200007:    add r0, r0, r2
+11000408:    addi r1, r1, #2
+2f000035:    rd32 r2, #0(sp)
+ff000808:    addi sp, sp, #4
+0000003b:    ret