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Convert arm_bitreversal2.S file to c code

Hi,

I am working on porting FFT functionality from CMSIS DSP library to another architecture.
Unfortunate I faced with problem that arm_bitreversal_32 function is implemented in assembler.

Does any body tried to convert it to C code?

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0 Yasuhiko Koumoto over 9 years ago in reply to Yasuhiko Koumoto

Hello,

I'm very sorry. I revised the code again.

This revision would be identical to the original.

Best regards.

Yasuhiko Koumoto.

void
arm_bitreversal_32 (uint32_t * pSrc, const uint16_t bitRevLen,
                    const uint16_t * pBitRevTable)
{
  uint32_t r7,r6,r5,r4,r3;
  if (bitRevLen <= 0)
    return;
  r3 = ((bitRevLen+1) >> 2);
  while (r3 > 0)
    {
      r7 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[3]);
      r6 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[2]);
      r5 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[1]);
      r4 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[0]);
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[3]) = r6;
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[2]) = r7;
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[1]) = r4;
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[0]) = r5;
      r7 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[3] + 4);
      r6 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[2] + 4);
      r5 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[1] + 4);
      r4 = *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[0] + 4);
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[3] + 4) = r6;
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[2] + 4) = r7;
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[1] + 4) = r4;
      *(uint32_t*)((uint8_t*) pSrc + pBitRevTable[0] + 4) = r5;
      pBitRevTable += 4;
      r3--;
    }
}

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