factorial

code/factorial/factorial.c

@@ -0,0 +1,28 @@
+#include <stdio.h>
+
+int factorial(int num) {
+  int i;      // $t1
+  int j;      // $t2
+  int temp;   // $t3
+  int sum;    // $t4
+ 
+  temp = 1;
+  sum = 1;
+  i = 1;
+  while (i <= num) {
+    sum = 0;
+    j = 0;
+    while (j < i) {
+      sum += temp;
+      j++;
+    }
+    temp = sum;
+    i++;
+  }
+  return sum;
+}
+
+int main() {
+  printf("fac(%d) = %d\n", 6, factorial(6));
+  return 0;
+}

code/factorial/factorial.s

@@ -0,0 +1,80 @@
+.psx
+.create "factorial.bin", 0x80010000
+
+; Entry Point of Code
+.org 0x80010000
+
+; Constant declaration
+BASE_ADDR equ 0x0000
+
+; Symbol Alias Table
+
+; Instructions
+; Load
+load_imm   equ li ; dst_reg, immeidate value
+; Store
+store_word equ sw ; src_reg, dst_address 
+; Addition
+add_s  equ add   ; dst_reg, reg_a, reg_b (signed)
+add_u  equ add   ; dst_reg, reg_a, reg_b (unsigned)
+add_si equ addi  ; dst_reg, src_reg, immediate value (signed)
+add_ui equ addiu ; dst_reg, src_reg, immediate value (unsigned)
+; Subtraction
+sub_s equ sub    ; 
+sub_u equ subu   ; 
+; Branch
+branch_equal    equ beq ; reg, value(reg, immediate), dst_label
+branch_gt_equal equ bge ; reg, value(reg, immediate), dst_label
+branch_gt       equ bgt ; reg, value(reg, immediate), dst_label
+branch_lt       equ blt ; reg, value(reg, immediate), dst_label
+; Jump
+jump       equ j   ; address:    immediate
+jump_nlink equ jal ; subroutine: immeidate
+jump_reg   equ jr  ; address:    register
+jump_nreg  equ jrl ; subroutine: register
+
+; Registers
+; Temporaries, may be changed by subroutines
+rtmp_0 equ $t0
+rtmp_1 equ $t1
+rtmp_2 equ $t2
+rtmp_3 equ $t3
+rtmp_4 equ $t4
+; Subroutine arguments
+rarg_0 equ $a0
+rarg_1 equ $a1
+rarg_2 equ $a2
+rarg_3 equ $a3
+; Subroutine return values
+rret_0 equ $v0
+rret_1 equ $v1
+
+main:
+		li rarg_0, 5
+	jump_nlink factorial
+
+; args:
+;	num: rarg_0
+.func factorial
+num        equ rarg_0
+id_term    equ rtmp_0
+id_product equ rtmp_1
+term       equ rtmp_2
+sum        equ rtmp_3
+	li term,    1
+	li sum,     1
+	li id_term, 1
+	loop_term: branch_gt id_term, num, break_loop_term :: nop
+		li sum,        0
+		li id_product, 0
+		loop_prod: branch_gt_equal id_product, id_term, break_loop_prod :: nop
+			add_s  sum,        sum,        term
+			add_si id_product, id_product, 1
+		jump loop_prod :: nop :: break_loop_prod:
+		move   term,    sum
+		add_si id_term, id_term, 1
+	jump loop_term :: nop :: break_loop_term:
+	move rret_0, sum
+.endfunc	
+
+.close