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40 lines
815 B
ArmAsm
40 lines
815 B
ArmAsm
.global Fib
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.text
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.align 4
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Fib: str x30, [sp, -16]!
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// If w0 is 0 or 1, take the branch to return w0.
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cmp w0, 1
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bls 99f
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// If we get here, we need to do the recursion.
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// Save the parameter on the stack so we can
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// get it back between recursions.
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// nthNumber to be stored at 16 off sp
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str w0, [sp, -16]! // +1
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// Execute Fib(nthNumber - 1)
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sub w0, w0, 1
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bl Fib
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// Fib(n-1) stored at 32 of sp
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str w0, [sp, -16]! // +2
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// Execute Fib(nthNumber - 2)
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ldr w0, [sp, 16]
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sub w0, w0, 2
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bl Fib
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// Restore the results of Fib(nthNumber - 1) and also
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// undo the stack change associated with preserving it.
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ldr w1, [sp], 16 // +1
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add w0, w0, w1
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// Undo the stack change due to storing nthNumber
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ldr w1, [sp], 16 // 0
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99: ldr x30, [sp], 16
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ret
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