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/arch/mips/math-emu/dp_tlong.c

http://github.com/mirrors/linux
C | 100 lines | 75 code | 9 blank | 16 comment | 31 complexity | 862028f9b96602fc77745b625865c752 MD5 | raw file
  1// SPDX-License-Identifier: GPL-2.0-only
  2/* IEEE754 floating point arithmetic
  3 * double precision: common utilities
  4 */
  5/*
  6 * MIPS floating point support
  7 * Copyright (C) 1994-2000 Algorithmics Ltd.
  8 */
  9
 10#include "ieee754dp.h"
 11
 12s64 ieee754dp_tlong(union ieee754dp x)
 13{
 14	u64 residue;
 15	int round;
 16	int sticky;
 17	int odd;
 18
 19	COMPXDP;
 20
 21	ieee754_clearcx();
 22
 23	EXPLODEXDP;
 24	FLUSHXDP;
 25
 26	switch (xc) {
 27	case IEEE754_CLASS_SNAN:
 28	case IEEE754_CLASS_QNAN:
 29		ieee754_setcx(IEEE754_INVALID_OPERATION);
 30		return ieee754di_indef();
 31
 32	case IEEE754_CLASS_INF:
 33		ieee754_setcx(IEEE754_INVALID_OPERATION);
 34		return ieee754di_overflow(xs);
 35
 36	case IEEE754_CLASS_ZERO:
 37		return 0;
 38
 39	case IEEE754_CLASS_DNORM:
 40	case IEEE754_CLASS_NORM:
 41		break;
 42	}
 43	if (xe >= 63) {
 44		/* look for valid corner case */
 45		if (xe == 63 && xs && xm == DP_HIDDEN_BIT)
 46			return -0x8000000000000000LL;
 47		/* Set invalid. We will only use overflow for floating
 48		   point overflow */
 49		ieee754_setcx(IEEE754_INVALID_OPERATION);
 50		return ieee754di_overflow(xs);
 51	}
 52	/* oh gawd */
 53	if (xe > DP_FBITS) {
 54		xm <<= xe - DP_FBITS;
 55	} else if (xe < DP_FBITS) {
 56		if (xe < -1) {
 57			residue = xm;
 58			round = 0;
 59			sticky = residue != 0;
 60			xm = 0;
 61		} else {
 62			/* Shifting a u64 64 times does not work,
 63			* so we do it in two steps. Be aware that xe
 64			* may be -1 */
 65			residue = xm << (xe + 1);
 66			residue <<= 63 - DP_FBITS;
 67			round = (residue >> 63) != 0;
 68			sticky = (residue << 1) != 0;
 69			xm >>= DP_FBITS - xe;
 70		}
 71		odd = (xm & 0x1) != 0x0;
 72		switch (ieee754_csr.rm) {
 73		case FPU_CSR_RN:
 74			if (round && (sticky || odd))
 75				xm++;
 76			break;
 77		case FPU_CSR_RZ:
 78			break;
 79		case FPU_CSR_RU:	/* toward +Infinity */
 80			if ((round || sticky) && !xs)
 81				xm++;
 82			break;
 83		case FPU_CSR_RD:	/* toward -Infinity */
 84			if ((round || sticky) && xs)
 85				xm++;
 86			break;
 87		}
 88		if ((xm >> 63) != 0) {
 89			/* This can happen after rounding */
 90			ieee754_setcx(IEEE754_INVALID_OPERATION);
 91			return ieee754di_overflow(xs);
 92		}
 93		if (round || sticky)
 94			ieee754_setcx(IEEE754_INEXACT);
 95	}
 96	if (xs)
 97		return -xm;
 98	else
 99		return xm;
100}