forked from Github_Repos/cvw
33 lines
816 B
ArmAsm
33 lines
816 B
ArmAsm
// sum.s
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// David_Harris@hmc.edu 24 December 2021
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// Add up numbers from 1 to N.
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// result in s0, i in s1, N in a0, return answer in a0
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//
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// long sum(long N) {
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// long result, i;
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// result = 0;
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// for (i=1; i<=N; i++) result = result + i;
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// return result;
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// }
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.global sum
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sum:
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addi sp, sp, -16 # make room to save s0 and s1 on the stack
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sd s0, 0(sp)
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sd s1, 8(sp)
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li s0, 0 # result = 0
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li s1, 1 # i = 1
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for: bgt s1, a0, done # exit loop if i > n
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add s0, s0, s1 # result = result + i
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addi s1, s1, 1 # i++
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j for # repeat
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done:
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mv a0, s0 # put result in a0 to return
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ld s0, 0(sp) # restore s0 and s1 from stack
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ld s1, 8(sp)
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addi sp, sp, 16
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ret # return from function
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