fdk-aac/libFDK/include/arm/scramble_arm.h

/* -----------------------------------------------------------------------------
Software License for The Fraunhofer FDK AAC Codec Library for Android

© Copyright  1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
Forschung e.V. All rights reserved.

 1.    INTRODUCTION
The Fraunhofer FDK AAC Codec Library for Android ("FDK AAC Codec") is software
that implements the MPEG Advanced Audio Coding ("AAC") encoding and decoding
scheme for digital audio. This FDK AAC Codec software is intended to be used on
a wide variety of Android devices.

AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient
general perceptual audio codecs. AAC-ELD is considered the best-performing
full-bandwidth communications codec by independent studies and is widely
deployed. AAC has been standardized by ISO and IEC as part of the MPEG
specifications.

Patent licenses for necessary patent claims for the FDK AAC Codec (including
those of Fraunhofer) may be obtained through Via Licensing
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already be covered under those patent licenses when it is used for those
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Commercially-licensed AAC software libraries, including floating-point versions
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5.    CONTACT INFORMATION

Fraunhofer Institute for Integrated Circuits IIS
Attention: Audio and Multimedia Departments - FDK AAC LL
Am Wolfsmantel 33
91058 Erlangen, Germany

www.iis.fraunhofer.de/amm
amm-info@iis.fraunhofer.de
----------------------------------------------------------------------------- */

/******************* Library for basic calculation routines ********************

   Author(s):

   Description: bitreversal of input data

*******************************************************************************/

#if !defined(SCRAMBLE_ARM_H)
#define SCRAMBLE_ARM_H

#if defined(FUNCTION_scramble)
#if defined(__GNUC__)

#define FUNCTION_scramble

#if defined(__ARM_ARCH_5TE__)
#define USE_LDRD_STRD /* LDRD requires 8 byte data alignment. */
#endif

inline void scramble(FIXP_DBL x[], INT n) {
  FDK_ASSERT(!(((INT)x) & (ALIGNMENT_DEFAULT - 1)));
  asm("mov     r2, #1;\n"     /* r2(m) = 1;           */
      "sub     r3, %1, #1;\n" /* r3 = n-1;            */
      "mov     r4, #0;\n"     /* r4(j) = 0;           */

      "scramble_m_loop%=:\n" /* {                    */
      "mov     r5, %1;\n"    /*  r5(k) = 1;          */

      "scramble_k_loop%=:\n"         /*  {                   */
      "mov     r5, r5, lsr #1;\n"    /*   k >>= 1;           */
      "eor     r4, r4, r5;\n"        /*   j ^=k;             */
      "ands    r10, r4, r5;\n"       /*   r10 = r4 & r5;      */
      "beq     scramble_k_loop%=;\n" /*  } while (r10 == 0);  */

      "cmp     r4, r2;\n" /*   if (r4 < r2) break;        */
      "bcc     scramble_m_loop_end%=;\n"

#ifdef USE_LDRD_STRD
      "mov     r5, r2, lsl #3;\n" /* m(r5) = r2*4*2               */
      "ldrd    r10, [%0, r5];\n"  /* r10 = x[r5], x7 = x[r5+1]     */
      "mov     r6, r4, lsl #3;\n" /* j(r6) = r4*4*2              */
      "ldrd    r8, [%0, r6];\n"   /* r8 = x[r6], r9 = x[r6+1];  */
      "strd    r10, [%0, r6];\n"  /* x[r6,r6+1] = r10,r11;        */
      "strd    r8, [%0, r5];\n"   /* x[r5,r5+1] = r8,r9;          */
#else
      "mov      r5, r2, lsl #3;\n" /* m(r5) = r2*4*2               */
      "ldr      r10, [%0, r5];\n"
      "mov      r6, r4, lsl #3;\n" /* j(r6) = r4*4*2              */
      "ldr      r11, [%0, r6];\n"

      "str      r10, [%0, r6];\n"
      "str      r11, [%0, r5];\n"

      "add      r5, r5, #4;"
      "ldr      r10, [%0, r5];\n"
      "add      r6, r6, #4;"
      "ldr      r11, [%0, r6];\n"
      "str      r10, [%0, r6];\n"
      "str      r11, [%0, r5];\n"
#endif
      "scramble_m_loop_end%=:\n"
      "add     r2, r2, #1;\n" /* r2++;                        */
      "cmp     r2, r3;\n"
      "bcc     scramble_m_loop%=;\n" /* } while (r2(m) < r3(n-1));   */
      :
      : "r"(x), "r"(n)
#ifdef USE_LDRD_STRD
      : "r2", "r3", "r4", "r5", "r10", "r11", "r8", "r9", "r6");
#else
      : "r2", "r3", "r4", "r5", "r10", "r11", "r6");
#endif
}
#else
/* Force C implementation if no assembler version available. */
#undef FUNCTION_scramble
#endif /* Toolchain selection. */

#endif /* defined(FUNCTION_scramble) */
#endif /* !defined(SCRAMBLE_ARM_H) */