CODEWITHSUNDEEP
c++ssesimdintrinsics
Rotem
Rotem

Reputation: 21947

Extract 4 SSE integers to 4 chars

Suppose I have a __m128i containing 4 32-bit integer values.

Is there some way I can store it inside a char[4], where the lower char from each int value is stored in a char value?

Desired result:

           r1          r2          r3          r4
__m128i    0x00000012  0x00000034  0x00000056  0x00000078

  |
  V

char[4]    0x12        0x34        0x56        0x78

SSE2 and below is preferred. Compiling on MSVC++.

Upvotes: 2

Views: 703

Answers (2)

Antonio
Antonio

Reputation: 20296

Just for completeness, with SSSE3 you can do it with only one shuffling operation using _mm_shuffle_epi8. See here. You do consume one register more though, it depends on what is more important for you.

Upvotes: 2

Marat Dukhan
Marat Dukhan

Reputation: 12273

With SSE2 you can use the following code:

char[4] array;
x = _mm_packs_epi32(x, x);
x = _mm_packus_epi16(x, x);
*((int*)array) = _mm_cvtsi128_si32(x);

Upvotes: 4

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