37 lines
732 B
Markdown
37 lines
732 B
Markdown
# sum
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Sum a slice of `uint64`s.
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[embedmd]:# (asm.go go /func main/ /^}/)
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```go
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func main() {
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TEXT("Sum", NOSPLIT, "func(xs []uint64) uint64")
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Doc("Sum returns the sum of the elements in xs.")
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ptr := Load(Param("xs").Base(), GP64())
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n := Load(Param("xs").Len(), GP64())
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Comment("Initialize sum register to zero.")
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s := GP64()
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XORQ(s, s)
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Label("loop")
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Comment("Loop until zero bytes remain.")
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CMPQ(n, Imm(0))
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JE(LabelRef("done"))
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Comment("Load from pointer and add to running sum.")
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ADDQ(Mem{Base: ptr}, s)
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Comment("Advance pointer, decrement byte count.")
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ADDQ(Imm(8), ptr)
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DECQ(n)
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JMP(LabelRef("loop"))
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Label("done")
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Comment("Store sum to return value.")
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Store(s, ReturnIndex(0))
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RET()
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Generate()
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}
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```
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