Source file src/runtime/internal/math/math.go
Documentation: runtime/internal/math
1 // Copyright 2018 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package math 6 7 import "runtime/internal/sys" 8 9 const MaxUintptr = ^uintptr(0) 10 11 // MulUintptr returns a * b and whether the multiplication overflowed. 12 // On supported platforms this is an intrinsic lowered by the compiler. 13 func MulUintptr(a, b uintptr) (uintptr, bool) { 14 if a|b < 1<<(4*sys.PtrSize) || a == 0 { 15 return a * b, false 16 } 17 overflow := b > MaxUintptr/a 18 return a * b, overflow 19 } 20 21 // Mul64 returns the 128-bit product of x and y: (hi, lo) = x * y 22 // with the product bits' upper half returned in hi and the lower 23 // half returned in lo. 24 // This is a copy from math/bits.Mul64 25 // On supported platforms this is an intrinsic lowered by the compiler. 26 func Mul64(x, y uint64) (hi, lo uint64) { 27 const mask32 = 1<<32 - 1 28 x0 := x & mask32 29 x1 := x >> 32 30 y0 := y & mask32 31 y1 := y >> 32 32 w0 := x0 * y0 33 t := x1*y0 + w0>>32 34 w1 := t & mask32 35 w2 := t >> 32 36 w1 += x0 * y1 37 hi = x1*y1 + w2 + w1>>32 38 lo = x * y 39 return 40 } 41