llvm/compiler-rt/lib/builtins/fp_trunc.h

//=== lib/fp_trunc.h - high precision -> low precision conversion *- C -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Set source and destination precision setting
//
//===----------------------------------------------------------------------===//

#ifndef FP_TRUNC_HEADER
#define FP_TRUNC_HEADER

#include "int_lib.h"

#if defined SRC_SINGLE
typedef float src_t;
typedef uint32_t src_rep_t;
#define SRC_REP_C …
static const int srcBits = sizeof(src_t) * CHAR_BIT;
static const int srcSigFracBits = 23;
// -1 accounts for the sign bit.
// srcBits - srcSigFracBits - 1
static const int srcExpBits = 8;

#elif defined SRC_DOUBLE
src_t;
src_rep_t;
#define SRC_REP_C …
static const int srcBits = …;
static const int srcSigFracBits = …;
// -1 accounts for the sign bit.
// srcBits - srcSigFracBits - 1
static const int srcExpBits = …;

#elif defined SRC_80
typedef xf_float src_t;
typedef __uint128_t src_rep_t;
#define SRC_REP_C …
// sign bit, exponent and significand occupy the lower 80 bits.
static const int srcBits = 80;
static const int srcSigFracBits = 63;
// -1 accounts for the sign bit.
// -1 accounts for the explicitly stored integer bit.
// srcBits - srcSigFracBits - 1 - 1
static const int srcExpBits = 15;

#elif defined SRC_QUAD
typedef tf_float src_t;
typedef __uint128_t src_rep_t;
#define SRC_REP_C …
static const int srcBits = sizeof(src_t) * CHAR_BIT;
static const int srcSigFracBits = 112;
// -1 accounts for the sign bit.
// srcBits - srcSigFracBits - 1
static const int srcExpBits = 15;

#else
#error Source should be double precision or quad precision!
#endif // end source precision

#if defined DST_DOUBLE
typedef double dst_t;
typedef uint64_t dst_rep_t;
#define DST_REP_C …
static const int dstBits = sizeof(dst_t) * CHAR_BIT;
static const int dstSigFracBits = 52;
// -1 accounts for the sign bit.
// dstBits - dstSigFracBits - 1
static const int dstExpBits = 11;

#elif defined DST_80
typedef xf_float dst_t;
typedef __uint128_t dst_rep_t;
#define DST_REP_C …
static const int dstBits = 80;
static const int dstSigFracBits = 63;
// -1 accounts for the sign bit.
// -1 accounts for the explicitly stored integer bit.
// dstBits - dstSigFracBits - 1 - 1
static const int dstExpBits = 15;

#elif defined DST_SINGLE
typedef float dst_t;
typedef uint32_t dst_rep_t;
#define DST_REP_C …
static const int dstBits = sizeof(dst_t) * CHAR_BIT;
static const int dstSigFracBits = 23;
// -1 accounts for the sign bit.
// dstBits - dstSigFracBits - 1
static const int dstExpBits = 8;

#elif defined DST_HALF
#ifdef COMPILER_RT_HAS_FLOAT16
dst_t;
#else
typedef uint16_t dst_t;
#endif
dst_rep_t;
#define DST_REP_C …
static const int dstBits = …;
static const int dstSigFracBits = …;
// -1 accounts for the sign bit.
// dstBits - dstSigFracBits - 1
static const int dstExpBits = …;

#elif defined DST_BFLOAT
typedef __bf16 dst_t;
typedef uint16_t dst_rep_t;
#define DST_REP_C …
static const int dstBits = sizeof(dst_t) * CHAR_BIT;
static const int dstSigFracBits = 7;
// -1 accounts for the sign bit.
// dstBits - dstSigFracBits - 1
static const int dstExpBits = 8;

#else
#error Destination should be single precision or double precision!
#endif // end destination precision

// TODO: These helper routines should be placed into fp_lib.h
// Currently they depend on macros/constants defined above.

static inline src_rep_t extract_sign_from_src(src_rep_t x) { … }

static inline src_rep_t extract_exp_from_src(src_rep_t x) { … }

static inline src_rep_t extract_sig_frac_from_src(src_rep_t x) { … }

static inline dst_rep_t construct_dst_rep(dst_rep_t sign, dst_rep_t exp, dst_rep_t sigFrac) { … }

// End of specialization parameters.  Two helper routines for conversion to and
// from the representation of floating-point data as integer values follow.

static inline src_rep_t srcToRep(src_t x) { … }

static inline dst_t dstFromRep(dst_rep_t x) { … }

#endif // FP_TRUNC_HEADER