39 lines
720 B
Go
39 lines
720 B
Go
// +build ignore
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package main
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import (
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. "github.com/mmcloughlin/avo/build"
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. "github.com/mmcloughlin/avo/operand"
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)
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func main() {
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TEXT("Sum", "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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// Initialize sum register to zero.
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s := GP64()
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XORQ(s, s)
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// Loop until zero bytes remain.
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Label("loop")
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CMPQ(n, Imm(0))
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JE(LabelRef("done"))
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// Load from pointer and add to running sum.
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ADDQ(Mem{Base: ptr}, s)
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// 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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// Store sum to return value.
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Label("done")
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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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