github.com/primecitizens/pcz/std@v0.2.1/core/emu64/emu64.go

// SPDX-License-Identifier: Apache-2.0
// Copyright 2023 The Prime Citizens
//
// Inferno's libkern/vlrt-arm.c
// https://bitbucket.org/inferno-os/inferno-os/src/master/libkern/vlrt-arm.c
//
//         Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
//         Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).  All rights reserved.
//         Portions Copyright 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

//go:build arm || 386 || mips || mipsle

package emu64

import (
	"unsafe"

	"github.com/primecitizens/pcz/std/core/assert"
)

const (
	sign32 = 1 << (32 - 1)
	sign64 = 1 << (64 - 1)
)

func Float64ToInt64(d float64) (y uint64) {
	_d2v(&y, d)
	return
}

func Float64ToUint64(d float64) (y uint64) {
	_d2v(&y, d)
	return
}

func Int64ToFloat64(y int64) float64 {
	if y < 0 {
		return -Uint64ToFloat64(-uint64(y))
	}
	return Uint64ToFloat64(uint64(y))
}

func Uint64ToFloat64(y uint64) float64 {
	hi := float64(uint32(y >> 32))
	lo := float64(uint32(y))
	d := hi*(1<<32) + lo
	return d
}

func Int64ToFloat32(y int64) float32 {
	if y < 0 {
		return -Uint64ToFloat32(-uint64(y))
	}
	return Uint64ToFloat32(uint64(y))
}

func Uint64ToFloat32(y uint64) float32 {
	// divide into top 18, mid 23, and bottom 23 bits.
	// (23-bit integers fit into a float32 without loss.)
	top := uint32(y >> 46)
	mid := uint32(y >> 23 & (1<<23 - 1))
	bot := uint32(y & (1<<23 - 1))
	if top == 0 {
		return float32(mid)*(1<<23) + float32(bot)
	}
	if bot != 0 {
		// Top is not zero, so the bits in bot
		// won't make it into the final mantissa.
		// In fact, the bottom bit of mid won't
		// make it into the mantissa either.
		// We only need to make sure that if top+mid
		// is about to round down in a round-to-even
		// scenario, and bot is not zero, we make it
		// round up instead.
		mid |= 1
	}
	return float32(top)*(1<<46) + float32(mid)*(1<<23)
}

func _d2v(y *uint64, d float64) {
	x := *(*uint64)(unsafe.Pointer(&d))

	xhi := uint32(x>>32)&0xfffff | 0x100000
	xlo := uint32(x)
	sh := 1075 - int32(uint32(x>>52)&0x7ff)

	var ylo, yhi uint32
	if sh >= 0 {
		sh := uint32(sh)
		/* v = (hi||lo) >> sh */
		if sh < 32 {
			if sh == 0 {
				ylo = xlo
				yhi = xhi
			} else {
				ylo = xlo>>sh | xhi<<(32-sh)
				yhi = xhi >> sh
			}
		} else {
			if sh == 32 {
				ylo = xhi
			} else if sh < 64 {
				ylo = xhi >> (sh - 32)
			}
		}
	} else {
		/* v = (hi||lo) << -sh */
		sh := uint32(-sh)
		if sh <= 11 {
			ylo = xlo << sh
			yhi = xhi<<sh | xlo>>(32-sh)
		} else {
			/* overflow */
			yhi = uint32(d) /* causes something awful */
		}
	}
	if x&sign64 != 0 {
		if ylo != 0 {
			ylo = -ylo
			yhi = ^yhi
		} else {
			yhi = -yhi
		}
	}

	*y = uint64(yhi)<<32 | uint64(ylo)
}

func Uint64Div(n, d uint64) uint64 {
	// Check for 32 bit operands
	if uint32(n>>32) == 0 && uint32(d>>32) == 0 {
		if uint32(d) == 0 {
			panicdivide()
		}
		return uint64(uint32(n) / uint32(d))
	}
	q, _ := dodiv(n, d)
	return q
}

func Uint64Mod(n, d uint64) uint64 {
	// Check for 32 bit operands
	if uint32(n>>32) == 0 && uint32(d>>32) == 0 {
		if uint32(d) == 0 {
			panicdivide()
		}
		return uint64(uint32(n) % uint32(d))
	}
	_, r := dodiv(n, d)
	return r
}

func Int64Div(n, d int64) int64 {
	// Check for 32 bit operands
	if int64(int32(n)) == n && int64(int32(d)) == d {
		if int32(n) == -0x80000000 && int32(d) == -1 {
			// special case: 32-bit -0x80000000 / -1 = -0x80000000,
			// but 64-bit -0x80000000 / -1 = 0x80000000.
			return 0x80000000
		}
		if int32(d) == 0 {
			panicdivide()
		}
		return int64(int32(n) / int32(d))
	}

	nneg := n < 0
	dneg := d < 0
	if nneg {
		n = -n
	}
	if dneg {
		d = -d
	}
	uq, _ := dodiv(uint64(n), uint64(d))
	q := int64(uq)
	if nneg != dneg {
		q = -q
	}
	return q
}

//go:nosplit
func Int64Mod(n, d int64) int64 {
	// Check for 32 bit operands
	if int64(int32(n)) == n && int64(int32(d)) == d {
		if int32(d) == 0 {
			panicdivide()
		}
		return int64(int32(n) % int32(d))
	}

	nneg := n < 0
	if nneg {
		n = -n
	}
	if d < 0 {
		d = -d
	}
	_, ur := dodiv(uint64(n), uint64(d))
	r := int64(ur)
	if nneg {
		r = -r
	}
	return r
}

//go:nosplit
func slowdodiv(n, d uint64) (q, r uint64) {
	if d == 0 {
		panicdivide()
	}

	// Set up the divisor and find the number of iterations needed.
	capn := n
	if n >= sign64 {
		capn = sign64
	}
	i := 0
	for d < capn {
		d <<= 1
		i++
	}

	for ; i >= 0; i-- {
		q <<= 1
		if n >= d {
			n -= d
			q |= 1
		}
		d >>= 1
	}
	return q, n
}

func panicdivide() { assert.Throw("integer", "divide", "by", "zero") }