forked from OSchip/llvm-project
320 lines
10 KiB
C
320 lines
10 KiB
C
//===-- lib/fp_lib.h - Floating-point utilities -------------------*- C -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a configuration header for soft-float routines in compiler-rt.
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// This file does not provide any part of the compiler-rt interface, but defines
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// many useful constants and utility routines that are used in the
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// implementation of the soft-float routines in compiler-rt.
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//
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// Assumes that float, double and long double correspond to the IEEE-754
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// binary32, binary64 and binary 128 types, respectively, and that integer
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// endianness matches floating point endianness on the target platform.
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//
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//===----------------------------------------------------------------------===//
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#ifndef FP_LIB_HEADER
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#define FP_LIB_HEADER
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#include "int_lib.h"
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#include "int_math.h"
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#include <limits.h>
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#include <stdbool.h>
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#include <stdint.h>
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// x86_64 FreeBSD prior v9.3 define fixed-width types incorrectly in
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// 32-bit mode.
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#if defined(__FreeBSD__) && defined(__i386__)
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#include <sys/param.h>
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#if __FreeBSD_version < 903000 // v9.3
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#define uint64_t unsigned long long
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#define int64_t long long
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#undef UINT64_C
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#define UINT64_C(c) (c##ULL)
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#endif
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#endif
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#if defined SINGLE_PRECISION
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typedef uint32_t rep_t;
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typedef int32_t srep_t;
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typedef float fp_t;
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#define REP_C UINT32_C
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#define significandBits 23
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static __inline int rep_clz(rep_t a) { return __builtin_clz(a); }
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// 32x32 --> 64 bit multiply
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static __inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
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const uint64_t product = (uint64_t)a * b;
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*hi = product >> 32;
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*lo = product;
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}
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COMPILER_RT_ABI fp_t __addsf3(fp_t a, fp_t b);
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#elif defined DOUBLE_PRECISION
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typedef uint64_t rep_t;
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typedef int64_t srep_t;
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typedef double fp_t;
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#define REP_C UINT64_C
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#define significandBits 52
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static __inline int rep_clz(rep_t a) {
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#if defined __LP64__
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return __builtin_clzl(a);
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#else
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if (a & REP_C(0xffffffff00000000))
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return __builtin_clz(a >> 32);
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else
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return 32 + __builtin_clz(a & REP_C(0xffffffff));
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#endif
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}
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#define loWord(a) (a & 0xffffffffU)
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#define hiWord(a) (a >> 32)
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// 64x64 -> 128 wide multiply for platforms that don't have such an operation;
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// many 64-bit platforms have this operation, but they tend to have hardware
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// floating-point, so we don't bother with a special case for them here.
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static __inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
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// Each of the component 32x32 -> 64 products
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const uint64_t plolo = loWord(a) * loWord(b);
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const uint64_t plohi = loWord(a) * hiWord(b);
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const uint64_t philo = hiWord(a) * loWord(b);
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const uint64_t phihi = hiWord(a) * hiWord(b);
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// Sum terms that contribute to lo in a way that allows us to get the carry
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const uint64_t r0 = loWord(plolo);
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const uint64_t r1 = hiWord(plolo) + loWord(plohi) + loWord(philo);
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*lo = r0 + (r1 << 32);
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// Sum terms contributing to hi with the carry from lo
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*hi = hiWord(plohi) + hiWord(philo) + hiWord(r1) + phihi;
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}
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#undef loWord
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#undef hiWord
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COMPILER_RT_ABI fp_t __adddf3(fp_t a, fp_t b);
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#elif defined QUAD_PRECISION
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#if __LDBL_MANT_DIG__ == 113 && defined(__SIZEOF_INT128__)
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#define CRT_LDBL_128BIT
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typedef __uint128_t rep_t;
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typedef __int128_t srep_t;
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typedef long double fp_t;
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#define REP_C (__uint128_t)
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// Note: Since there is no explicit way to tell compiler the constant is a
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// 128-bit integer, we let the constant be casted to 128-bit integer
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#define significandBits 112
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static __inline int rep_clz(rep_t a) {
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const union {
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__uint128_t ll;
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#if _YUGA_BIG_ENDIAN
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struct {
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uint64_t high, low;
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} s;
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#else
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struct {
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uint64_t low, high;
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} s;
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#endif
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} uu = {.ll = a};
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uint64_t word;
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uint64_t add;
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if (uu.s.high) {
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word = uu.s.high;
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add = 0;
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} else {
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word = uu.s.low;
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add = 64;
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}
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return __builtin_clzll(word) + add;
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}
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#define Word_LoMask UINT64_C(0x00000000ffffffff)
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#define Word_HiMask UINT64_C(0xffffffff00000000)
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#define Word_FullMask UINT64_C(0xffffffffffffffff)
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#define Word_1(a) (uint64_t)((a >> 96) & Word_LoMask)
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#define Word_2(a) (uint64_t)((a >> 64) & Word_LoMask)
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#define Word_3(a) (uint64_t)((a >> 32) & Word_LoMask)
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#define Word_4(a) (uint64_t)(a & Word_LoMask)
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// 128x128 -> 256 wide multiply for platforms that don't have such an operation;
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// many 64-bit platforms have this operation, but they tend to have hardware
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// floating-point, so we don't bother with a special case for them here.
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static __inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
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const uint64_t product11 = Word_1(a) * Word_1(b);
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const uint64_t product12 = Word_1(a) * Word_2(b);
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const uint64_t product13 = Word_1(a) * Word_3(b);
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const uint64_t product14 = Word_1(a) * Word_4(b);
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const uint64_t product21 = Word_2(a) * Word_1(b);
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const uint64_t product22 = Word_2(a) * Word_2(b);
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const uint64_t product23 = Word_2(a) * Word_3(b);
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const uint64_t product24 = Word_2(a) * Word_4(b);
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const uint64_t product31 = Word_3(a) * Word_1(b);
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const uint64_t product32 = Word_3(a) * Word_2(b);
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const uint64_t product33 = Word_3(a) * Word_3(b);
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const uint64_t product34 = Word_3(a) * Word_4(b);
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const uint64_t product41 = Word_4(a) * Word_1(b);
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const uint64_t product42 = Word_4(a) * Word_2(b);
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const uint64_t product43 = Word_4(a) * Word_3(b);
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const uint64_t product44 = Word_4(a) * Word_4(b);
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const __uint128_t sum0 = (__uint128_t)product44;
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const __uint128_t sum1 = (__uint128_t)product34 + (__uint128_t)product43;
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const __uint128_t sum2 =
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(__uint128_t)product24 + (__uint128_t)product33 + (__uint128_t)product42;
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const __uint128_t sum3 = (__uint128_t)product14 + (__uint128_t)product23 +
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(__uint128_t)product32 + (__uint128_t)product41;
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const __uint128_t sum4 =
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(__uint128_t)product13 + (__uint128_t)product22 + (__uint128_t)product31;
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const __uint128_t sum5 = (__uint128_t)product12 + (__uint128_t)product21;
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const __uint128_t sum6 = (__uint128_t)product11;
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const __uint128_t r0 = (sum0 & Word_FullMask) + ((sum1 & Word_LoMask) << 32);
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const __uint128_t r1 = (sum0 >> 64) + ((sum1 >> 32) & Word_FullMask) +
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(sum2 & Word_FullMask) + ((sum3 << 32) & Word_HiMask);
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*lo = r0 + (r1 << 64);
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*hi = (r1 >> 64) + (sum1 >> 96) + (sum2 >> 64) + (sum3 >> 32) + sum4 +
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(sum5 << 32) + (sum6 << 64);
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}
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#undef Word_1
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#undef Word_2
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#undef Word_3
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#undef Word_4
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#undef Word_HiMask
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#undef Word_LoMask
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#undef Word_FullMask
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#endif // __LDBL_MANT_DIG__ == 113 && __SIZEOF_INT128__
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#else
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#error SINGLE_PRECISION, DOUBLE_PRECISION or QUAD_PRECISION must be defined.
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#endif
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#if defined(SINGLE_PRECISION) || defined(DOUBLE_PRECISION) || \
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defined(CRT_LDBL_128BIT)
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#define typeWidth (sizeof(rep_t) * CHAR_BIT)
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#define exponentBits (typeWidth - significandBits - 1)
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#define maxExponent ((1 << exponentBits) - 1)
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#define exponentBias (maxExponent >> 1)
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#define implicitBit (REP_C(1) << significandBits)
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#define significandMask (implicitBit - 1U)
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#define signBit (REP_C(1) << (significandBits + exponentBits))
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#define absMask (signBit - 1U)
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#define exponentMask (absMask ^ significandMask)
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#define oneRep ((rep_t)exponentBias << significandBits)
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#define infRep exponentMask
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#define quietBit (implicitBit >> 1)
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#define qnanRep (exponentMask | quietBit)
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static __inline rep_t toRep(fp_t x) {
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const union {
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fp_t f;
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rep_t i;
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} rep = {.f = x};
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return rep.i;
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}
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static __inline fp_t fromRep(rep_t x) {
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const union {
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fp_t f;
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rep_t i;
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} rep = {.i = x};
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return rep.f;
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}
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static __inline int normalize(rep_t *significand) {
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const int shift = rep_clz(*significand) - rep_clz(implicitBit);
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*significand <<= shift;
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return 1 - shift;
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}
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static __inline void wideLeftShift(rep_t *hi, rep_t *lo, int count) {
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*hi = *hi << count | *lo >> (typeWidth - count);
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*lo = *lo << count;
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}
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static __inline void wideRightShiftWithSticky(rep_t *hi, rep_t *lo,
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unsigned int count) {
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if (count < typeWidth) {
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const bool sticky = (*lo << (typeWidth - count)) != 0;
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*lo = *hi << (typeWidth - count) | *lo >> count | sticky;
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*hi = *hi >> count;
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} else if (count < 2 * typeWidth) {
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const bool sticky = *hi << (2 * typeWidth - count) | *lo;
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*lo = *hi >> (count - typeWidth) | sticky;
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*hi = 0;
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} else {
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const bool sticky = *hi | *lo;
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*lo = sticky;
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*hi = 0;
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}
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}
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// Implements logb methods (logb, logbf, logbl) for IEEE-754. This avoids
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// pulling in a libm dependency from compiler-rt, but is not meant to replace
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// it (i.e. code calling logb() should get the one from libm, not this), hence
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// the __compiler_rt prefix.
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static __inline fp_t __compiler_rt_logbX(fp_t x) {
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rep_t rep = toRep(x);
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int exp = (rep & exponentMask) >> significandBits;
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// Abnormal cases:
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// 1) +/- inf returns +inf; NaN returns NaN
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// 2) 0.0 returns -inf
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if (exp == maxExponent) {
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if (((rep & signBit) == 0) || (x != x)) {
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return x; // NaN or +inf: return x
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} else {
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return -x; // -inf: return -x
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}
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} else if (x == 0.0) {
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// 0.0: return -inf
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return fromRep(infRep | signBit);
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}
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if (exp != 0) {
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// Normal number
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return exp - exponentBias; // Unbias exponent
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} else {
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// Subnormal number; normalize and repeat
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rep &= absMask;
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const int shift = 1 - normalize(&rep);
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exp = (rep & exponentMask) >> significandBits;
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return exp - exponentBias - shift; // Unbias exponent
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}
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}
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#endif
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#if defined(SINGLE_PRECISION)
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static __inline fp_t __compiler_rt_logbf(fp_t x) {
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return __compiler_rt_logbX(x);
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}
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#elif defined(DOUBLE_PRECISION)
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static __inline fp_t __compiler_rt_logb(fp_t x) {
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return __compiler_rt_logbX(x);
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}
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#elif defined(QUAD_PRECISION)
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#if defined(CRT_LDBL_128BIT)
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static __inline fp_t __compiler_rt_logbl(fp_t x) {
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return __compiler_rt_logbX(x);
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}
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#else
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// The generic implementation only works for ieee754 floating point. For other
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// floating point types, continue to rely on the libm implementation for now.
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static __inline long double __compiler_rt_logbl(long double x) {
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return crt_logbl(x);
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}
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#endif
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#endif
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#endif // FP_LIB_HEADER
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