Multiplication Intrinsics

These Intel® Supplemental Streaming SIMD Extensions 3 (Intel® SSSE3) intrinsics are used for multiplication. The prototypes for these intrinsics are in tmmintrin.h. You can also use the ia32intrin.h header file for these intrinsics.

Multiply signed and unsigned bytes, add horizontal pair of signed words, pack saturated signed words.

Interpreting a as array of unsigned 8-bit integers, b as arrays of signed 8-bit integers, and r as arrays of 16-bit signed integers:

for (i = 0; i < 8; i++) {

  r[i] = signed_saturate_to_word(a[2*i+1] * b[2*i+1] + a[2*i]*b[2*i]);

}

Multiply signed and unsigned bytes, add horizontal pair of signed words, pack saturated signed words.

Interpreting a as array of unsigned 8-bit integers, b as arrays of signed 8-bit integers, and r as arrays of 16-bit signed integers:

for (i = 0; i < 4; i++) {

  r[i] = signed_saturate_to_word(a[2*i+1] * b[2*i+1] + a[2*i]*b[2*i]);

}

Multiply signed words, scale and round signed dwords, pack high 16-bits.

Interpreting a, b, and r as arrays of signed 16-bit integers:

for (i = 0; i < 8; i++) {

  r[i] =  (( (int32)((a[i] * b[i]) >> 14) + 1) >> 1) & 0xFFFF;

}

Multiply signed words, scale and round signed dwords, pack high 16-bits.

Interpreting a, b, and r as arrays of signed 16-bit integers:

for (i = 0; i < 4; i++) {

  r[i] =  (( (int32)((a[i] * b[i]) >> 14) + 1) >> 1) & 0xFFFF;

}