compiler-rt/lib/builtins/fp_trunc.h

   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
  19 typedef float src_t;
  20 typedef uint32_t src_rep_t;
  21 #define SRC_REP_C UINT32_C
  22 static const int srcBits = sizeof(src_t) * CHAR_BIT;
  23 static const int srcSigFracBits = 23;
  24 // -1 accounts for the sign bit.
  25 // srcBits - srcSigFracBits - 1
  26 static const int srcExpBits = 8;
  27
  28 #elif defined SRC_DOUBLE
  29 typedef double src_t;
  30 typedef uint64_t src_rep_t;
  31 #define SRC_REP_C UINT64_C
  32 static const int srcBits = sizeof(src_t) * CHAR_BIT;
  33 static const int srcSigFracBits = 52;
  34 // -1 accounts for the sign bit.
  35 // srcBits - srcSigFracBits - 1
  36 static const int srcExpBits = 11;
  37
  38 #elif defined SRC_QUAD
  39 typedef tf_float src_t;
  40 typedef __uint128_t src_rep_t;
  41 #define SRC_REP_C (__uint128_t)
  42 static const int srcBits = sizeof(src_t) * CHAR_BIT;
  43 static const int srcSigFracBits = 112;
  44 // -1 accounts for the sign bit.
  45 // srcBits - srcSigFracBits - 1
  46 static 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
  53 typedef double dst_t;
  54 typedef uint64_t dst_rep_t;
  55 #define DST_REP_C UINT64_C
  56 static const int dstBits = sizeof(dst_t) * CHAR_BIT;
  57 static const int dstSigFracBits = 52;
  58 // -1 accounts for the sign bit.
  59 // dstBits - dstSigFracBits - 1
  60 static const int dstExpBits = 11;
  61
  62 #elif defined DST_80
  63 typedef xf_float dst_t;
  64 typedef __uint128_t dst_rep_t;
  65 #define DST_REP_C (__uint128_t)
  66 static const int dstBits = 80;
  67 static 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
  71 static const int dstExpBits = 15;
  72
  73 #elif defined DST_SINGLE
  74 typedef float dst_t;
  75 typedef uint32_t dst_rep_t;
  76 #define DST_REP_C UINT32_C
  77 static const int dstBits = sizeof(dst_t) * CHAR_BIT;
  78 static const int dstSigFracBits = 23;
  79 // -1 accounts for the sign bit.
  80 // dstBits - dstSigFracBits - 1
  81 static const int dstExpBits = 8;
  82
  83 #elif defined DST_HALF
  84 #ifdef COMPILER_RT_HAS_FLOAT16
  85 typedef _Float16 dst_t;
  86 #else
  87 typedef uint16_t dst_t;
  88 #endif
  89 typedef uint16_t dst_rep_t;
  90 #define DST_REP_C UINT16_C
  91 static const int dstBits = sizeof(dst_t) * CHAR_BIT;
  92 static const int dstSigFracBits = 10;
  93 // -1 accounts for the sign bit.
  94 // dstBits - dstSigFracBits - 1
  95 static const int dstExpBits = 5;
  96
  97 #elif defined DST_BFLOAT
  98 typedef __bf16 dst_t;
  99 typedef uint16_t dst_rep_t;
 100 #define DST_REP_C UINT16_C
 101 static const int dstBits = sizeof(dst_t) * CHAR_BIT;
 102 static const int dstSigFracBits = 7;
 103 // -1 accounts for the sign bit.
 104 // dstBits - dstSigFracBits - 1
 105 static 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
 114 static 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
 119 static 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
 125 static 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
 130 static 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
 142 static 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
 150 static 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