ARM Compiler armcc User Guide : 12.16 _

12.16 __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.

Syntax

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.

Return value

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.

Examples

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;
}

Related reference

10.147 ARMv6 SIMD intrinsics

Related information

SHADD8

ARM and Thumb instruction summary

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