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 12 s64 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 } 101