mirror of https://github.com/gtank/ristretto255
19 lines
659 B
Go
19 lines
659 B
Go
// Copyright (c) 2017 George Tankersley. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package radix51
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import "unsafe"
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// mul64x64 multiples two 64-bit numbers and adds them to two accumulators.
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// This function is written to ensure it inlines. I am so sorry.
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func mul64x64(lo, hi, a, b uint64) (ol uint64, oh uint64) {
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t1 := (a>>32)*(b&0xFFFFFFFF) + ((a & 0xFFFFFFFF) * (b & 0xFFFFFFFF) >> 32)
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t2 := (a&0xFFFFFFFF)*(b>>32) + (t1 & 0xFFFFFFFF)
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ol = (a * b) + lo
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cmp := ol < lo
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oh = hi + (a>>32)*(b>>32) + t1>>32 + t2>>32 + uint64(*(*byte)(unsafe.Pointer(&cmp)))
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return
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}
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