//=-lib/fp_extend_impl.inc - low precision -> high precision conversion -*-- -//

//

//                     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 narrower to a wider

// IEEE-754 floating-point type.  The constants and types defined following the

// includes below parameterize the conversion.

//

// 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

// *widening* operations; if you need to convert to a *narrower* floating-point

// type (e.g. double -> float), 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.  You also may

// run into trouble finding an appropriate CLZ function for wide source types;

// you will likely need to roll your own on some platforms.

//

// 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 "fp_extend.h"

static __inline dst_t __extendXfYf2__(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 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 srcQNaN = SRC_REP_C(1) << (srcSigBits - 1);

    const src_rep_t srcNaNCode = srcQNaN - 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 dst_rep_t dstMinNormal = DST_REP_C(1) << dstSigBits;

    // Break a into a sign and representation of the absolute value

    dst_rep_t absResult;

    // If sizeof(src_rep_t) < sizeof(int), the subtraction result is promoted

    // to (signed) int.  To avoid that, explicitly cast to src_rep_t.

        // a is a normal number.

        // Extend to the destination type by shifting the significand and

        // exponent into the proper position and rebiasing the exponent.

    }

        // a is NaN or infinity.

        // Conjure the result by beginning with infinity, then setting the qNaN

        // bit (if needed) and right-aligning the rest of the trailing NaN

        // payload field.

        absResult = (dst_rep_t)dstInfExp << dstSigBits;

    }

        // a is denormal.

        // renormalize the significand and clear the leading bit, then insert

        // the correct adjusted exponent in the destination type.

    }

    else {

        // a is zero.

        absResult = 0;

    }

    // Apply the signbit to (dst_t)abs(a).

}