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Diffstat (limited to 'compiler-rt/lib/builtins/floatdidf.c')
-rw-r--r-- | compiler-rt/lib/builtins/floatdidf.c | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/compiler-rt/lib/builtins/floatdidf.c b/compiler-rt/lib/builtins/floatdidf.c new file mode 100644 index 000000000000..8f887314b9e1 --- /dev/null +++ b/compiler-rt/lib/builtins/floatdidf.c @@ -0,0 +1,103 @@ +//===-- floatdidf.c - Implement __floatdidf -------------------------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// +// +// This file implements __floatdidf for the compiler_rt library. +// +//===----------------------------------------------------------------------===// + +#include "int_lib.h" + +// Returns: convert a to a double, rounding toward even. + +// Assumption: double is a IEEE 64 bit floating point type +// di_int is a 64 bit integral type + +// seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm +// mmmm + +#ifndef __SOFT_FP__ +// Support for systems that have hardware floating-point; we'll set the inexact +// flag as a side-effect of this computation. + +COMPILER_RT_ABI double __floatdidf(di_int a) { + static const double twop52 = 4503599627370496.0; // 0x1.0p52 + static const double twop32 = 4294967296.0; // 0x1.0p32 + + union { + int64_t x; + double d; + } low = {.d = twop52}; + + const double high = (int32_t)(a >> 32) * twop32; + low.x |= a & INT64_C(0x00000000ffffffff); + + const double result = (high - twop52) + low.d; + return result; +} + +#else +// Support for systems that don't have hardware floating-point; there are no +// flags to set, and we don't want to code-gen to an unknown soft-float +// implementation. + +COMPILER_RT_ABI double __floatdidf(di_int a) { + if (a == 0) + return 0.0; + const unsigned N = sizeof(di_int) * CHAR_BIT; + const di_int s = a >> (N - 1); + a = (a ^ s) - s; + int sd = N - __builtin_clzll(a); // number of significant digits + int e = sd - 1; // exponent + if (sd > DBL_MANT_DIG) { + // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx + // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR + // 12345678901234567890123456 + // 1 = msb 1 bit + // P = bit DBL_MANT_DIG-1 bits to the right of 1 + // Q = bit DBL_MANT_DIG bits to the right of 1 + // R = "or" of all bits to the right of Q + switch (sd) { + case DBL_MANT_DIG + 1: + a <<= 1; + break; + case DBL_MANT_DIG + 2: + break; + default: + a = ((du_int)a >> (sd - (DBL_MANT_DIG + 2))) | + ((a & ((du_int)(-1) >> ((N + DBL_MANT_DIG + 2) - sd))) != 0); + }; + // finish: + a |= (a & 4) != 0; // Or P into R + ++a; // round - this step may add a significant bit + a >>= 2; // dump Q and R + // a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits + if (a & ((du_int)1 << DBL_MANT_DIG)) { + a >>= 1; + ++e; + } + // a is now rounded to DBL_MANT_DIG bits + } else { + a <<= (DBL_MANT_DIG - sd); + // a is now rounded to DBL_MANT_DIG bits + } + double_bits fb; + fb.u.s.high = ((su_int)s & 0x80000000) | // sign + ((e + 1023) << 20) | // exponent + ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high + fb.u.s.low = (su_int)a; // mantissa-low + return fb.f; +} +#endif + +#if defined(__ARM_EABI__) +#if defined(COMPILER_RT_ARMHF_TARGET) +AEABI_RTABI double __aeabi_l2d(di_int a) { return __floatdidf(a); } +#else +COMPILER_RT_ALIAS(__floatdidf, __aeabi_l2d) +#endif +#endif |