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
 
#include "fl/stl/noexcept.h"
 
namespace fl {
namespace third_party {
 
#if (defined _WIN32 && !defined _WIN32_WCE && defined _M_IX86) || (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 */
 
__inline int32_t MULSHIFT32(int32_t x, int32_t y)
{
    __asm {
        mov     eax, x
        imul    y
        mov     eax, edx
    }
}
 
__inline int FASTABS(int x)
{
    int sign;
 
    sign = x >> (sizeof(int) * 8 - 1);
    x ^= sign;
    x -= sign;
 
    return x;
}
 
__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
 */
#ifdef __CW32__
typedef long long Word64;
#else
typedef __int64 Word64;
#endif
 
__inline Word64 MADD64(Word64 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)); */
}
 
__inline Word64 SHL64(Word64 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
        }
    }
}
 
__inline Word64 SAR64(Word64 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
int32_t MULSHIFT32(int32_t x, int32_t y);
 
__inline int FASTABS(int x)
{
    int sign;
 
    sign = x >> (sizeof(int) * 8 - 1);
    x ^= sign;
    x -= sign;
 
    return x;
}
 
__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
 
__inline int32_t MULSHIFT32(int32_t x, int32_t 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;
}
 
__inline int FASTABS(int x)
{
    int t=0; /*Really is not necessary to initialiaze only to avoid warning*/
 
    __asm {
        eor t, x, x, asr #31
        sub t, t, x, asr #31
    }
 
    return t;
}
 
__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)
 
#if defined(ARM7DI)
    
typedef long long Word64;
 
__inline int32_t MULSHIFT32(int32_t x, int32_t y) {
    return x * y;
}
 
__inline Word64 SAR64(Word64 x, int n) {
    return x >>= n;
}
 
 
typedef union _U64 {
    Word64 w64;
    struct {
        /* x86 = little endian */
        unsigned int lo32;
        signed int   hi32;
    } r;
} U64;
 
__inline Word64 MADD64(Word64 sum64, int x, int y)
{
    sum64 += (Word64)x * (Word64)y;
 
    return sum64;
}
 
#else
 
__inline int32_t MULSHIFT32(int32_t x, int32_t 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;
}
 
#endif
 
__inline int FASTABS(int x)
{
    int t=0; /*Really is not necessary to initialiaze only to avoid warning*/
 
    __asm__ volatile (
        "eor %0,%2,%2, asr #31;"
        "sub %0,%1,%2, asr #31;"
        : "=&r" (t)
        : "0" (t), "r" (x)
     );
 
    return t;
}
 
__inline int CLZ(int x)
{
    int numZeros;
 
    if (!x)
        return (sizeof(int) * 8);
 
    numZeros = 0;
    while (!(x & 0x80000000)) {
        numZeros++;
        x <<= 1;
    }
 
    return numZeros;
}
 
#else
 
#ifdef __riscv
 
typedef long long Word64;
 
__inline int32_t MULSHIFT32(int32_t x, int32_t y)
{
    unsigned int result = 0;
    asm volatile ("mulh %0, %1, %2" : "=r"(result): "r"(x), "r"(y));
    return result;
}
 
__inline int FASTABS(int x) 
{
    int sign;
 
    sign = x >> (sizeof(int) * 8 - 1);
    x ^= sign;
    x -= sign;
 
    return x;
}
 
__inline int CLZ(int x)
{
    int numZeros;
 
    if (!x)
        return (sizeof(int) * 8);
 
    numZeros = 0;
    while (!(x & 0x80000000)) {
        numZeros++;
        x <<= 1;
    } 
 
    return numZeros;
}
 
__inline Word64 MADD64(Word64 sum, int a, int b)
{
    unsigned int result_hi = 0;
    unsigned int result_lo = 0;
    asm volatile ("mulh %0, %1, %2" : "=r"(result_hi): "r"(a), "r"(b));
    asm volatile ("mul  %0, %1, %2" : "=r"(result_lo): "r"(a), "r"(b));
 
    Word64 result = result_hi;
    result <<= 32;
    result += result_lo;
    result += sum;
    return result;
}
 
__inline Word64 SHL64(Word64 x, int n)
{
    return (x<<n);
}
 
__inline Word64 SAR64(Word64 x, int n)
{
    return (x >> n);
}
 
#elif defined(__xtensa__)
 
#include "xtensa/config/core-isa.h"
 
typedef long long Word64;
 
__inline Word64 MADD64(Word64 sum64, int x, int y)
{
    return (sum64 + ((long long)x * y));
}
 
#if XCHAL_HAVE_MUL32_HIGH
 
__inline int32_t MULSHIFT32(int32_t x, int32_t 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 doesn't matter
     *   which one is returned. (If this were a function call, returning y (R1) would
     *   require an extra "mov r0, r1")
     */
    int ret;
    asm volatile ("mulsh %0, %1, %2" : "=r" (ret) : "r" (x), "r" (y));
    return ret;
}
 
#else
 
// Fallback for Xtensa without MUL32_HIGH (e.g., ESP8266)
__inline int32_t MULSHIFT32(int32_t x, int32_t y) FL_NOEXCEPT
{
    Word64 result = ((Word64) x) * y;
    return (int32_t)(result >> 32);
}
 
#endif
 
#if XCHAL_HAVE_ABS
 
__inline int FASTABS(int x)
{
    int ret;
    asm volatile ("abs %0, %1" : "=r" (ret) : "r" (x));
    return ret;
}
 
#else
 
// Fallback for Xtensa without ABS instruction (e.g., ESP8266)
__inline int FASTABS(int x)
{
    int sign;
    sign = x >> (sizeof(int) * 8 - 1);
    x ^= sign;
    x -= sign;
    return x;
}
 
#endif
 
__inline Word64 SAR64(Word64 x, int n) FL_NOEXCEPT
{
    return x >> n;
}
 
__inline int CLZ(int x)
{
    return __builtin_clz(x);
}
 
#else
 
typedef long long Word64;

__inline int32_t MULSHIFT32(int32_t x, int32_t y) FL_NOEXCEPT
{
    Word64 result = ((Word64) x) * y;
 
    return (int32_t)(result >> 32);
}

__inline int32_t FASTABS(int32_t x) FL_NOEXCEPT
{
    int32_t sign;
 
    sign = x >> (sizeof(int32_t) * 8 - 1);
    x ^= sign;
    x -= sign;
 
    return x;
}

__inline int32_t CLZ(int32_t x) FL_NOEXCEPT
{
    int32_t numZeros;
 
    if (!x)
        return (sizeof(int32_t) * 8);
 
    numZeros = 0;
    while (!(x & 0x80000000)) {
        numZeros++;
        x <<= 1;
    }
 
    return numZeros;
}

__inline Word64 MADD64(Word64 sum64, int x, int y) FL_NOEXCEPT
{
    sum64 += (Word64)x * (Word64)y;
 
    return sum64;
}

__inline Word64 SHL64(Word64 x, int n) FL_NOEXCEPT
{
    return ((Word64) x) << n;
}

__inline Word64 SAR64(Word64 x, int n) FL_NOEXCEPT
{
    return x >> n;
}
 
#endif
 
#endif  /* platforms */
 
} /* namespace third_party */
} /* namespace fl */
 
#endif /* _ASSEMBLY_H */