2.3-InternetRadio/nutos/nut/include/contrib/hxmp3/assembly.h

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/**************************************************************************************
 * Fixed-point MP3 decoder
 * Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com)
 * June 2003
 *
 * assembly.h - assembly language functions and prototypes for supported platforms
 *
 * - inline rountines with access to 64-bit multiply results
 * - x86 (_WIN32) and ARM (ARM_ADS, _WIN32_WCE) versions included
 * - some inline functions are mix of asm and C for speed
 * - some functions are in native asm files, so only the prototype is given here
 *
 * MULSHIFT32(x, y)    signed multiply of two 32-bit integers (x and y), returns top 32 bits of 64-bit result
 * FASTABS(x)          branchless absolute value of signed integer x
 * CLZ(x)              count leading zeros in x
 * MADD64(sum, x, y)   (Windows only) sum [64-bit] += x [32-bit] * y [32-bit]
 * SHL64(sum, x, y)    (Windows only) 64-bit left shift using __int64
 * SAR64(sum, x, y)    (Windows only) 64-bit right shift using __int64
 */

#ifndef _ASSEMBLY_H
#define _ASSEMBLY_H

#if (defined _WIN32 && !defined _WIN32_WCE) || (defined __WINS__ && defined _SYMBIAN) || defined(_OPENWAVE_SIMULATOR) || defined(WINCE_EMULATOR)    /* Symbian emulator for Ix86 */

#pragma warning( disable : 4035 )   /* complains about inline asm not returning a value */

static __inline int MULSHIFT32(int x, int y)
{
    __asm {
        mov     eax, x
        imul    y
        mov     eax, edx
    }
}

static __inline int FASTABS(int x)
{
    int sign;

    sign = x >> (sizeof(int) * 8 - 1);
    x ^= sign;
    x -= sign;

    return x;
}

static __inline int CLZ(int x)
{
    int numZeros;

    if (!x)
        return (sizeof(int) * 8);

    numZeros = 0;
    while (!(x & 0x80000000)) {
        numZeros++;
        x <<= 1;
    }

    return numZeros;
}

/* MADD64, SHL64, SAR64:
 * write in assembly to avoid dependency on run-time lib for 64-bit shifts, muls
 *  (sometimes compiler thunks to function calls instead of code generating)
 * required for Symbian emulator
 */
static __inline __int64 MADD64(__int64 sum, int x, int y)
{
    unsigned int sumLo = ((unsigned int *)&sum)[0];
    int sumHi = ((int *)&sum)[1];

    __asm {
        mov     eax, x
        imul    y
        add     eax, sumLo
        adc     edx, sumHi
    }

    /* equivalent to return (sum + ((__int64)x * y)); */
}

static __inline __int64 SHL64(__int64 x, int n)
{
    unsigned int xLo = ((unsigned int *)&x)[0];
    int xHi = ((int *)&x)[1];
    unsigned char nb = (unsigned char)n;

    if (n < 32) {
        __asm {
            mov     edx, xHi
            mov     eax, xLo
            mov     cl, nb
            shld    edx, eax, cl
            shl     eax, cl
        }
    } else if (n < 64) {
        /* shl masks cl to 0x1f */
        __asm {
            mov     edx, xLo
            mov     cl, nb
            xor     eax, eax
            shl     edx, cl
        }
    } else {
        __asm {
            xor     edx, edx
            xor     eax, eax
        }
    }
}

static __inline __int64 SAR64(__int64 x, int n)
{
    unsigned int xLo = ((unsigned int *)&x)[0];
    int xHi = ((int *)&x)[1];
    unsigned char nb = (unsigned char)n;

    if (n < 32) {
        __asm {
            mov     edx, xHi
            mov     eax, xLo
            mov     cl, nb
            shrd    eax, edx, cl
            sar     edx, cl
        }
    } else if (n < 64) {
        /* sar masks cl to 0x1f */
        __asm {
            mov     edx, xHi
            mov     eax, xHi
            mov     cl, nb
            sar     edx, 31
            sar     eax, cl
        }
    } else {
        __asm {
            sar     xHi, 31
            mov     eax, xHi
            mov     edx, xHi
        }
    }
}

#elif (defined _WIN32) && (defined _WIN32_WCE)

/* use asm function for now (EVC++ 3.0 does horrible job compiling __int64 version) */
#define MULSHIFT32  xmp3_MULSHIFT32
int MULSHIFT32(int x, int y);

static __inline int FASTABS(int x)
{
    int sign;

    sign = x >> (sizeof(int) * 8 - 1);
    x ^= sign;
    x -= sign;

    return x;
}

static __inline int CLZ(int x)
{
    int numZeros;

    if (!x)
        return (sizeof(int) * 8);

    numZeros = 0;
    while (!(x & 0x80000000)) {
        numZeros++;
        x <<= 1;
    }

    return numZeros;
}

#elif defined ARM_ADS

static __inline int MULSHIFT32(int x, int y)
{
    /* important rules for smull RdLo, RdHi, Rm, Rs:
     *     RdHi and Rm can't be the same register
     *     RdLo and Rm can't be the same register
     *     RdHi and RdLo can't be the same register
     * Note: Rs determines early termination (leading sign bits) so if you want to specify
     *   which operand is Rs, put it in the SECOND argument (y)
     * For inline assembly, x and y are not assumed to be R0, R1 so it shouldn't matter
     *   which one is returned. (If this were a function call, returning y (R1) would
     *   require an extra "mov r0, r1")
     */
    int zlow;
    __asm {
        smull zlow,y,x,y
    }

    return y;
}

static __inline int FASTABS(int x)
{
    int t;

    __asm {
        eor t, x, x, asr #31
        sub t, t, x, asr #31
    }

    return t;
}

static __inline int CLZ(int x)
{
    int numZeros;

    if (!x)
        return (sizeof(int) * 8);

    numZeros = 0;
    while (!(x & 0x80000000)) {
        numZeros++;
        x <<= 1;
    }

    return numZeros;
}

#elif defined(__GNUC__) && defined(__arm__)

static __inline int MULSHIFT32(int x, int y)
{
    /* important rules for smull RdLo, RdHi, Rm, Rs:
     *     RdHi and Rm can't be the same register
     *     RdLo and Rm can't be the same register
     *     RdHi and RdLo can't be the same register
     * Note: Rs determines early termination (leading sign bits) so if you want to specify
     *   which operand is Rs, put it in the SECOND argument (y)
     * For inline assembly, x and y are not assumed to be R0, R1 so it shouldn't matter
     *   which one is returned. (If this were a function call, returning y (R1) would
     *   require an extra "mov r0, r1")
     */
    int zlow;
    __asm__ volatile ("smull %0,%1,%2,%3" : "=&r" (zlow), "=r" (y) : "r" (x), "1" (y)) ;

    return y;
}

static __inline int FASTABS(int x)
{
    int t = 0;

    __asm__ volatile (
        "eor %0,%2,%2, asr #31;"
        "sub %0,%1,%2, asr #31;"
        : "=&r" (t)
        : "0" (t), "r" (x)
     );

    return t;
}

static __inline int CLZ(int x)
{
    int numZeros;

    if (!x)
        return (sizeof(int) * 8);

    numZeros = 0;
    while (!(x & 0x80000000)) {
        numZeros++;
        x <<= 1;
    }

    return numZeros;
}

#else

#error Unsupported platform in assembly.h

#endif  /* platforms */

#endif /* _ASSEMBLY_H */