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_QUAD
39typedef tf_float src_t;
40typedef __uint128_t src_rep_t;
41#define SRC_REP_C (__uint128_t)
42static const int srcBits = sizeof(src_t) * CHAR_BIT;
43static const int srcSigFracBits = 112;
44// -1 accounts for the sign bit.
45// srcBits - srcSigFracBits - 1
46static const int srcExpBits = 15;
47
48#else
49#error Source should be double precision or quad precision!
50#endif // end source precision
51
52#if defined DST_DOUBLE
53typedef double dst_t;
54typedef uint64_t dst_rep_t;
55#define DST_REP_C UINT64_C
56static const int dstBits = sizeof(dst_t) * CHAR_BIT;
57static const int dstSigFracBits = 52;
58// -1 accounts for the sign bit.
59// dstBits - dstSigFracBits - 1
60static const int dstExpBits = 11;
61
62#elif defined DST_80
63typedef xf_float dst_t;
64typedef __uint128_t dst_rep_t;
65#define DST_REP_C (__uint128_t)
66static const int dstBits = 80;
67static const int dstSigFracBits = 63;
68// -1 accounts for the sign bit.
69// -1 accounts for the explicitly stored integer bit.
70// dstBits - dstSigFracBits - 1 - 1
71static const int dstExpBits = 15;
72
73#elif defined DST_SINGLE
74typedef float dst_t;
75typedef uint32_t dst_rep_t;
76#define DST_REP_C UINT32_C
77static const int dstBits = sizeof(dst_t) * CHAR_BIT;
78static const int dstSigFracBits = 23;
79// -1 accounts for the sign bit.
80// dstBits - dstSigFracBits - 1
81static const int dstExpBits = 8;
82
83#elif defined DST_HALF
84#ifdef COMPILER_RT_HAS_FLOAT16
85typedef _Float16 dst_t;
86#else
87typedef uint16_t dst_t;
88#endif
89typedef uint16_t dst_rep_t;
90#define DST_REP_C UINT16_C
91static const int dstBits = sizeof(dst_t) * CHAR_BIT;
92static const int dstSigFracBits = 10;
93// -1 accounts for the sign bit.
94// dstBits - dstSigFracBits - 1
95static const int dstExpBits = 5;
96
97#elif defined DST_BFLOAT
98typedef __bf16 dst_t;
99typedef uint16_t dst_rep_t;
100#define DST_REP_C UINT16_C
101static const int dstBits = sizeof(dst_t) * CHAR_BIT;
102static const int dstSigFracBits = 7;
103// -1 accounts for the sign bit.
104// dstBits - dstSigFracBits - 1
105static const int dstExpBits = 8;
106
107#else
108#error Destination should be single precision or double precision!
109#endif // end destination precision
110
111// TODO: These helper routines should be placed into fp_lib.h
112// Currently they depend on macros/constants defined above.
113
114static inline src_rep_t extract_sign_from_src(src_rep_t x) {
115 const src_rep_t srcSignMask = SRC_REP_C(1) << (srcBits - 1);
116 return (x & srcSignMask) >> (srcBits - 1);
117}
118
119static inline src_rep_t extract_exp_from_src(src_rep_t x) {
120 const int srcSigBits = srcBits - 1 - srcExpBits;
121 const src_rep_t srcExpMask = ((SRC_REP_C(1) << srcExpBits) - 1) << srcSigBits;
122 return (x & srcExpMask) >> srcSigBits;
123}
124
125static inline src_rep_t extract_sig_frac_from_src(src_rep_t x) {
126 const src_rep_t srcSigFracMask = (SRC_REP_C(1) << srcSigFracBits) - 1;
127 return x & srcSigFracMask;
128}
129
130static inline dst_rep_t construct_dst_rep(dst_rep_t sign, dst_rep_t exp, dst_rep_t sigFrac) {
131 dst_rep_t result = (sign << (dstBits - 1)) | (exp << (dstBits - 1 - dstExpBits)) | sigFrac;
132 // Set the explicit integer bit in F80 if present.
133 if (dstBits == 80 && exp) {
134 result |= (DST_REP_C(1) << dstSigFracBits);
135 }
136 return result;
137}
138
139// End of specialization parameters. Two helper routines for conversion to and
140// from the representation of floating-point data as integer values follow.
141
142static inline src_rep_t srcToRep(src_t x) {
143 const union {
144 src_t f;
145 src_rep_t i;
146 } rep = {.f = x};
147 return rep.i;
148}
149
150static inline dst_t dstFromRep(dst_rep_t x) {
151 const union {
152 dst_t f;
153 dst_rep_t i;
154 } rep = {.i = x};
155 return rep.f;
156}
157
158#endif // FP_TRUNC_HEADER
159

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