_mm_alignr_epi8
Microsoft Specific
Emits the Supplemental Streaming SIMD Extensions 3 (SSSE3) instruction palignr to extract a 128-bit byte aligned value.
__m128i _mm_alignr_epi8(
__m128i a,
__m128i b,
const int ralign
);
Parameters
[in] a
A 128-bit parameter that contains sixteen 8-bit integers.[in] b
A 128-bit parameter that contains sixteen 8-bit integers.[in] ralign
A constant that specifies how many bytes the interim result will be shifted to the right.
Return value
r := (CONCAT(a, b) >> (ralign * 8)) & 0xffffffffffffffff
Requirements
Intrinsic |
Architecture |
|---|---|
_mm_alignr_epi8 |
x86, x64 |
Header file <tmmintrin.h>
Remarks
r is the 128-bit result value.
CONCAT(a, b) is the 256-bit unsigned intermediate value that is a concatenation of parameters a and b. The result is this intermediate value shifted right by ralign bytes.
If ralign > 32, the result value is zero.
Before using this intrinsic, software must ensure that the processor supports the instruction.
Example
// _mm_alignr_epi8
#include <stdio.h>
#include <tmmintrin.h>
int main () {
__m128i a, b;
a.m128i_u32[3] = 0x01234567;
a.m128i_u32[2] = 0x89ABDCEF;
a.m128i_u32[1] = 0x01234567;
a.m128i_u32[0] = 0x89ABCDEF;
b.m128i_u32[3] = 0xFFFFEEEE;
b.m128i_u32[2] = 0xDDDDCCCC;
b.m128i_u32[1] = 0xBBBBAAAA;
b.m128i_u32[0] = 0x99998888;
// A right align value of four should remove the lowest 4 bytes of "b"
__m128i res = _mm_alignr_epi8( a, b, 4 );
printf_s("Original a: 0x%016I64x%016I64x\nOriginal b: 0x%016I64x%016I64x\n",
a.m128i_u64[1], a.m128i_u64[0],
b.m128i_u64[1], b.m128i_u64[0]);
printf_s("Result res: 0x%016I64x%016I64x\n",
res.m128i_u64[1], res.m128i_u64[0]);
return 0;
}
Original a: 0x0123456789abdcef0123456789abcdef
Original b: 0xffffeeeeddddccccbbbbaaaa99998888
Result res: 0x89abcdefffffeeeeddddccccbbbbaaaa