Add: loop and multiplication source code test | expend instruction memory size | Fix: on empty test file

tb/test_source_code/tb_risc_v_cpu/loop.S

@@ -0,0 +1,22 @@
+/*
+ *  0:zero, 1:ra, 2:sp, 3:gp, 4:tp, 5:t0-2, 8:s0/fp
+ *  9:s1, 10:a0-7, 18:s2-11, 28:t3-6
+ */
+
+li      t0, 0  # R[5]=0
+li      t1, 10 # R[6]=10
+loop_pos_start:
+bge     t0, t1, loop_pos_end
+addi    t0, t0, 1
+j		loop_pos_start
+loop_pos_end:
+
+li      a0, 10  # R[10]=10
+loop_neg_start:
+ble     a0, zero, loop_neg_end
+addi    a0, a0, -1
+j		loop_neg_start
+loop_neg_end:
+
+# R[5]=10
+# R[10]=0

tb/test_source_code/tb_risc_v_cpu/multiplication.S

@@ -0,0 +1,63 @@
+/*
+ *  0:zero, 1:ra, 2:sp, 3:gp, 4:tp, 5:t0-2, 8:s0/fp
+ *  9:s1, 10:a0-7, 18:s2-11, 28:t3-6
+ */
+
+j test
+
+mult:
+li a0, 0
+li a2, 1
+mult_loop_start:
+blt t1, a2, mult_loop_end
+and a1, t1, 1
+beq a1, zero, mult_even_compute
+add a0, a0, t2
+mult_even_compute:
+add t2, t2, t2
+srl t1, t1, 1
+j mult_loop_start
+mult_loop_end:
+jalr ra, t0, 0
+
+test:
+li t1, 0
+li t2, 0
+jal t0, mult
+nop # R[10]=0
+li t1, 0
+li t2, 1
+jal t0, mult
+nop # R[10]=0
+li t1, 1
+li t2, 0
+jal t0, mult
+nop # R[10]=0
+li t1, 1
+li t2, 1
+jal t0, mult
+nop # R[10]=1
+li t1, 2
+li t2, 1
+jal t0, mult
+nop # R[10]=2
+li t1, 1
+li t2, 3
+jal t0, mult
+nop # R[10]=3
+li t1, 2
+li t2, 2
+jal t0, mult
+nop # R[10]=4
+li t1, 2
+li t2, 3
+jal t0, mult
+nop # R[10]=6
+li t1, 5
+li t2, 3
+jal t0, mult
+nop # R[10]=15
+li t1, 5
+li t2, 25
+jal t0, mult
+nop # R[10]=125