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Diffstat (limited to 'lib/truncdfsf2.c')
| -rw-r--r-- | lib/truncdfsf2.c | 168 |
1 files changed, 0 insertions, 168 deletions
diff --git a/lib/truncdfsf2.c b/lib/truncdfsf2.c deleted file mode 100644 index 61c909a22d8a9..0000000000000 --- a/lib/truncdfsf2.c +++ /dev/null @@ -1,168 +0,0 @@ -//===-- lib/truncdfsf2.c - double -> single conversion ------------*- C -*-===// -// -// The LLVM Compiler Infrastructure -// -// This file is dual licensed under the MIT and the University of Illinois Open -// Source Licenses. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements a fairly generic conversion from a wider to a narrower -// IEEE-754 floating-point type in the default (round to nearest, ties to even) -// rounding mode. The constants and types defined following the includes below -// parameterize the conversion. -// -// This routine can be trivially adapted to support conversions to -// half-precision or from quad-precision. It does not support types that don't -// use the usual IEEE-754 interchange formats; specifically, some work would be -// needed to adapt it to (for example) the Intel 80-bit format or PowerPC -// double-double format. -// -// Note please, however, that this implementation is only intended to support -// *narrowing* operations; if you need to convert to a *wider* floating-point -// type (e.g. float -> double), then this routine will not do what you want it -// to. -// -// It also requires that integer types at least as large as both formats -// are available on the target platform; this may pose a problem when trying -// to add support for quad on some 32-bit systems, for example. -// -// Finally, the following assumptions are made: -// -// 1. floating-point types and integer types have the same endianness on the -// target platform -// -// 2. quiet NaNs, if supported, are indicated by the leading bit of the -// significand field being set -// -//===----------------------------------------------------------------------===// - -#include "int_lib.h" - -typedef double src_t; -typedef uint64_t src_rep_t; -#define SRC_REP_C UINT64_C -static const int srcSigBits = 52; - -typedef float dst_t; -typedef uint32_t dst_rep_t; -#define DST_REP_C UINT32_C -static const int dstSigBits = 23; - -// 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) { - const union { src_t f; src_rep_t i; } rep = {.f = x}; - return rep.i; -} - -static inline dst_t dstFromRep(dst_rep_t x) { - const union { dst_t f; dst_rep_t i; } rep = {.i = x}; - return rep.f; -} - -// End helper routines. Conversion implementation follows. - -ARM_EABI_FNALIAS(d2f, truncdfsf2) - -COMPILER_RT_ABI dst_t -__truncdfsf2(src_t a) { - - // Various constants whose values follow from the type parameters. - // Any reasonable optimizer will fold and propagate all of these. - const int srcBits = sizeof(src_t)*CHAR_BIT; - const int srcExpBits = srcBits - srcSigBits - 1; - const int srcInfExp = (1 << srcExpBits) - 1; - const int srcExpBias = srcInfExp >> 1; - - const src_rep_t srcMinNormal = SRC_REP_C(1) << srcSigBits; - const src_rep_t significandMask = srcMinNormal - 1; - const src_rep_t srcInfinity = (src_rep_t)srcInfExp << srcSigBits; - const src_rep_t srcSignMask = SRC_REP_C(1) << (srcSigBits + srcExpBits); - const src_rep_t srcAbsMask = srcSignMask - 1; - const src_rep_t roundMask = (SRC_REP_C(1) << (srcSigBits - dstSigBits)) - 1; - const src_rep_t halfway = SRC_REP_C(1) << (srcSigBits - dstSigBits - 1); - - const int dstBits = sizeof(dst_t)*CHAR_BIT; - const int dstExpBits = dstBits - dstSigBits - 1; - const int dstInfExp = (1 << dstExpBits) - 1; - const int dstExpBias = dstInfExp >> 1; - - const int underflowExponent = srcExpBias + 1 - dstExpBias; - const int overflowExponent = srcExpBias + dstInfExp - dstExpBias; - const src_rep_t underflow = (src_rep_t)underflowExponent << srcSigBits; - const src_rep_t overflow = (src_rep_t)overflowExponent << srcSigBits; - - const dst_rep_t dstQNaN = DST_REP_C(1) << (dstSigBits - 1); - const dst_rep_t dstNaNCode = dstQNaN - 1; - - // Break a into a sign and representation of the absolute value - const src_rep_t aRep = srcToRep(a); - const src_rep_t aAbs = aRep & srcAbsMask; - const src_rep_t sign = aRep & srcSignMask; - dst_rep_t absResult; - - if (aAbs - underflow < aAbs - overflow) { - // The exponent of a is within the range of normal numbers in the - // destination format. We can convert by simply right-shifting with - // rounding and adjusting the exponent. - absResult = aAbs >> (srcSigBits - dstSigBits); - absResult -= (dst_rep_t)(srcExpBias - dstExpBias) << dstSigBits; - - const src_rep_t roundBits = aAbs & roundMask; - - // Round to nearest - if (roundBits > halfway) - absResult++; - - // Ties to even - else if (roundBits == halfway) - absResult += absResult & 1; - } - - else if (aAbs > srcInfinity) { - // a is NaN. - // Conjure the result by beginning with infinity, setting the qNaN - // bit and inserting the (truncated) trailing NaN field. - absResult = (dst_rep_t)dstInfExp << dstSigBits; - absResult |= dstQNaN; - absResult |= aAbs & dstNaNCode; - } - - else if (aAbs > overflow) { - // a overflows to infinity. - absResult = (dst_rep_t)dstInfExp << dstSigBits; - } - - else { - // a underflows on conversion to the destination type or is an exact - // zero. The result may be a denormal or zero. Extract the exponent - // to get the shift amount for the denormalization. - const int aExp = aAbs >> srcSigBits; - const int shift = srcExpBias - dstExpBias - aExp + 1; - - const src_rep_t significand = (aRep & significandMask) | srcMinNormal; - - // Right shift by the denormalization amount with sticky. - if (shift > srcSigBits) { - absResult = 0; - } else { - const bool sticky = significand << (srcBits - shift); - src_rep_t denormalizedSignificand = significand >> shift | sticky; - absResult = denormalizedSignificand >> (srcSigBits - dstSigBits); - const src_rep_t roundBits = denormalizedSignificand & roundMask; - // Round to nearest - if (roundBits > halfway) - absResult++; - // Ties to even - else if (roundBits == halfway) - absResult += absResult & 1; - } - } - - // Apply the signbit to (dst_t)abs(a). - const dst_rep_t result = absResult | sign >> (srcBits - dstBits); - return dstFromRep(result); - -} |