1//=== lib/fp_trunc.h - high precision -> low precision conversion *- C -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Set source and destination precision setting
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef FP_TRUNC_HEADER
14#define FP_TRUNC_HEADER
15
16#include "int_lib.h"
17
18#if defined SRC_SINGLE
19typedef float src_t;
20typedef uint32_t src_rep_t;
21#define SRC_REP_C UINT32_C
22static const int srcBits = sizeof(src_t) * CHAR_BIT;
23static const int srcSigFracBits = 23;
24// -1 accounts for the sign bit.
25// srcBits - srcSigFracBits - 1
26static const int srcExpBits = 8;
27
28#elif defined SRC_DOUBLE
29typedef double src_t;
30typedef uint64_t src_rep_t;
31#define SRC_REP_C UINT64_C
32static const int srcBits = sizeof(src_t) * CHAR_BIT;
33static const int srcSigFracBits = 52;
34// -1 accounts for the sign bit.
35// srcBits - srcSigFracBits - 1
36static const int srcExpBits = 11;
37
38#elif defined SRC_80
39typedef xf_float src_t;
40typedef __uint128_t src_rep_t;
41#define SRC_REP_C (__uint128_t)
42// sign bit, exponent and significand occupy the lower 80 bits.
43static const int srcBits = 80;
44static const int srcSigFracBits = 63;
45// -1 accounts for the sign bit.
46// -1 accounts for the explicitly stored integer bit.
47// srcBits - srcSigFracBits - 1 - 1
48static const int srcExpBits = 15;
49
50#elif defined SRC_QUAD
51typedef tf_float src_t;
52typedef __uint128_t src_rep_t;
53#define SRC_REP_C (__uint128_t)
54static const int srcBits = sizeof(src_t) * CHAR_BIT;
55static const int srcSigFracBits = 112;
56// -1 accounts for the sign bit.
57// srcBits - srcSigFracBits - 1
58static const int srcExpBits = 15;
59
60#else
61#error Source should be double precision or quad precision!
62#endif // end source precision
63
64#if defined DST_DOUBLE
65typedef double dst_t;
66typedef uint64_t dst_rep_t;
67#define DST_REP_C UINT64_C
68static const int dstBits = sizeof(dst_t) * CHAR_BIT;
69static const int dstSigFracBits = 52;
70// -1 accounts for the sign bit.
71// dstBits - dstSigFracBits - 1
72static const int dstExpBits = 11;
73
74#elif defined DST_80
75typedef xf_float dst_t;
76typedef __uint128_t dst_rep_t;
77#define DST_REP_C (__uint128_t)
78static const int dstBits = 80;
79static const int dstSigFracBits = 63;
80// -1 accounts for the sign bit.
81// -1 accounts for the explicitly stored integer bit.
82// dstBits - dstSigFracBits - 1 - 1
83static const int dstExpBits = 15;
84
85#elif defined DST_SINGLE
86typedef float dst_t;
87typedef uint32_t dst_rep_t;
88#define DST_REP_C UINT32_C
89static const int dstBits = sizeof(dst_t) * CHAR_BIT;
90static const int dstSigFracBits = 23;
91// -1 accounts for the sign bit.
92// dstBits - dstSigFracBits - 1
93static const int dstExpBits = 8;
94
95#elif defined DST_HALF
96#ifdef COMPILER_RT_HAS_FLOAT16
97typedef _Float16 dst_t;
98#else
99typedef uint16_t dst_t;
100#endif
101typedef uint16_t dst_rep_t;
102#define DST_REP_C UINT16_C
103static const int dstBits = sizeof(dst_t) * CHAR_BIT;
104static const int dstSigFracBits = 10;
105// -1 accounts for the sign bit.
106// dstBits - dstSigFracBits - 1
107static const int dstExpBits = 5;
108
109#elif defined DST_BFLOAT
110typedef __bf16 dst_t;
111typedef uint16_t dst_rep_t;
112#define DST_REP_C UINT16_C
113static const int dstBits = sizeof(dst_t) * CHAR_BIT;
114static const int dstSigFracBits = 7;
115// -1 accounts for the sign bit.
116// dstBits - dstSigFracBits - 1
117static const int dstExpBits = 8;
118
119#else
120#error Destination should be single precision or double precision!
121#endif // end destination precision
122
123// TODO: These helper routines should be placed into fp_lib.h
124// Currently they depend on macros/constants defined above.
125
126static inline src_rep_t extract_sign_from_src(src_rep_t x) {
127 const src_rep_t srcSignMask = SRC_REP_C(1) << (srcBits - 1);
128 return (x & srcSignMask) >> (srcBits - 1);
129}
130
131static inline src_rep_t extract_exp_from_src(src_rep_t x) {
132 const int srcSigBits = srcBits - 1 - srcExpBits;
133 const src_rep_t srcExpMask = ((SRC_REP_C(1) << srcExpBits) - 1) << srcSigBits;
134 return (x & srcExpMask) >> srcSigBits;
135}
136
137static inline src_rep_t extract_sig_frac_from_src(src_rep_t x) {
138 const src_rep_t srcSigFracMask = (SRC_REP_C(1) << srcSigFracBits) - 1;
139 return x & srcSigFracMask;
140}
141
142static inline dst_rep_t construct_dst_rep(dst_rep_t sign, dst_rep_t exp, dst_rep_t sigFrac) {
143 dst_rep_t result = (sign << (dstBits - 1)) | (exp << (dstBits - 1 - dstExpBits)) | sigFrac;
144 // Set the explicit integer bit in F80 if present.
145 if (dstBits == 80 && exp) {
146 result |= (DST_REP_C(1) << dstSigFracBits);
147 }
148 return result;
149}
150
151// End of specialization parameters. Two helper routines for conversion to and
152// from the representation of floating-point data as integer values follow.
153
154static inline src_rep_t srcToRep(src_t x) {
155 const union {
156 src_t f;
157 src_rep_t i;
158 } rep = {.f = x};
159 return rep.i;
160}
161
162static inline dst_t dstFromRep(dst_rep_t x) {
163 const union {
164 dst_t f;
165 dst_rep_t i;
166 } rep = {.i = x};
167 return rep.f;
168}
169
170#endif // FP_TRUNC_HEADER
171

source code of compiler-rt/lib/builtins/fp_trunc.h