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.globl factorial

.text
factorial:
        lda         $sp,-0x10($sp)
        stq         $ra,0x8($sp)
        stq         $s0,0x0($sp)
        bis         $zero,$a0,$s0
        zapnot      $s0,0xf,$a0
        cmpule      $a0,0x1,$a0
        bne         $a0,1f
        br          $zero,2f
1:      lda         $v0,0x1($zero)
        br          $zero,3f
2:      lda         $v0,-0x1($zero)
        addl        $s0,$v0,$v0
        zapnot      $v0,0xf,$a0
        bsr         $ra,factorial
        mull        $s0,$v0,$v0
3:      ldq         $s0,0x0($sp)
        ldq         $ra,0x8($sp)
        lda         $sp,0x10($sp)
        ret         $zero,($ra),0x1
