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Compiler Reference Guide

Conventions and Feedback Introduction Compiler Command-line Options Language Extensions Compiler-specific Features C and C++ Implementation Details Semihosting ARMv6 SIMD Instruction Intrinsics ARMv6 SIMD intrinsics by prefix ARMv6 SIMD intrinsics, summary descriptions, byte ARMv6 SIMD intrinsics, compatible processors and a ARMv6 SIMD instruction intrinsics and APSR GE flag __qadd16 intrinsic __qadd8 intrinsic __qasx intrinsic __qsax intrinsic __qsub16 intrinsic __qsub8 intrinsic __sadd16 intrinsic __sadd8 intrinsic __sasx intrinsic __sel intrinsic __shadd16 intrinsic __shadd8 intrinsic __shasx intrinsic __shsax intrinsic __shsub16 intrinsic __shsub8 intrinsic __smlad intrinsic __smladx intrinsic __smlald intrinsic __smlaldx intrinsic __smlsd intrinsic __smlsdx intrinsic __smlsld intrinsic __smlsldx intrinsic __smuad intrinsic __smuadx intrinsic __smusd intrinsic __smusdx intrinsic __ssat16 intrinsic __ssax intrinsic __ssub16 intrinsic __ssub8 intrinsic __sxtab16 intrinsic __sxtb16 intrinsic __uadd16 intrinsic __uadd8 intrinsic __uasx intrinsic __uhadd16 intrinsic __uhadd8 intrinsic __uhasx intrinsic __uhsax intrinsic __uhsub16 intrinsic __uhsub8 intrinsic __uqadd16 intrinsic __uqadd8 intrinsic __uqasx intrinsic __uqsax intrinsic __uqsub16 intrinsic __uqsub8 intrinsic __usad8 intrinsic __usada8 intrinsic __usax intrinsic __usat16 intrinsic __usub16 intrinsic __usub8 intrinsic __uxtab16 intrinsic __uxtb16 intrinsic Via File Syntax Standard C Implementation Definition Standard C++ Implementation Definition C and C++ Compiler Implementation Limits

Compiler Reference Guide

__shadd8 intrinsic

__shadd8 intrinsic

This intrinsic inserts a SHADD8 instruction into the instruction stream generated by the compiler. It enables you to perform four signed 8-bit integer additions, halving the results.

unsigned int __shadd8(unsigned int val1, unsigned int val2)

where:

val1

holds the first four 8-bit summands

val2

holds the second four 8-bit summands.

The __shadd8 intrinsic returns:

  • the halved addition of the first bytes from each operand, in the first byte of the return value

  • the halved addition of the second bytes from each operand, in the second byte of the return value

  • the halved addition of the third bytes from each operand, in the third byte of the return value

  • the halved addition of the fourth bytes from each operand, in the fourth byte of the return value.

Example:

unsigned int add_and_halve(unsigned int val1, unsigned int val2)
{
  unsigned int res;

    res = __shadd8(val1,val2); /* res[7:0] = (val1[7:0] + val2[7:0]) >> 1
                                  res[15:8] = (val1[15:8] + val2[15:8]) >> 1
                                  res[23:16] = (val1[23:16] + val2[23:16]) >> 1
                                  res[31:24] = (val1[31:24] + val2[31:24]) >> 1
                               */
    return res;
}

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