43 lines
811 B
Go
43 lines
811 B
Go
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// +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("Triangle", NOSPLIT, "func(n uint64) uint64")
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Doc("Triangle computes the nth triangle number.")
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n := Load(Param("n"), 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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// Use two labels for the top of the loop.
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Label("loop_even")
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Label("loop_odd")
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Comment("Loop until n is zero.")
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CMPQ(n, Imm(0))
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JE(LabelRef("done"))
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Comment("Add n to sum.")
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ADDQ(n, s)
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Comment("Decrement n.")
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DECQ(n)
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Comment("Jump to one of the loop labels depending on parity.")
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TESTQ(U32(1), n)
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JZ(LabelRef("loop_even"))
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JMP(LabelRef("loop_odd"))
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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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