_mm_cmpistrm
Microsoft Specific
Emits the Streaming SIMD Extensions 4 (SSE4) instruction pcmpistrm. This instruction compares two parameters.
__m128i _mm_cmpistrm (
__m128i a,
__m128i b,
const int mode
);
Parameters
Parameter |
Description |
[in] a |
A string fragment with a maximum size of 16 byte characters or 8 word characters. |
[in] b |
A string fragment with a maximum size of 16 byte characters or 8 word characters. |
[in] mode |
A constant that indicates if characters are bytes or words, the type of comparison to do, and the format of the returned value. |
Return value
Either the computed mask of MaxSize bits or its expansion to a 128-bit parameter. If the return value is expanded, each bit of the result mask is expanded to a byte or a word.
The pcmpistrm instruction computes the result mask, where bit0, bit1, bit2… in the mask correspond to the result of the operation on a0, a1, a2… in a.
Requirements
Intrinsic |
Architecture |
_mm_cmpistrm |
x86, x64 |
Header file <nmmintrin.h>
Remarks
b0, b1, b2… indicate the first, second, third… characters in b. b0 is stored in the least significant bits of b. The same notation applies to a. MaxSize is either 16 for byte characters or 8 for word characters. This is the maximum number of characters that fit into a __m128i data type. The lower 7 bits in mode determine the type of the input characters, which comparison to run, and the format of the return value. They are described in the following:
mode in binary |
Predefined constant |
Description |
xxxxxx00 |
_SIDD_UBYTE_OPS |
a and b contain strings of unsigned 8-bit characters. |
xxxxxx01 |
_SIDD_UWORD_OPS |
a and b contain strings of unsigned 16-bit characters. |
xxxxxx10 |
_SIDD_SBYTE_OPS |
a and b contain strings of signed 8-bit characters. |
xxxxxx11 |
_SIDD_SWORD_OPS |
a and b contain strings of signed 16-bit characters. |
xxxx00xx |
_SIDD_CMP_EQUAL_ANY |
Find if equal any mode: For each character c in a, determine whether any character in b is equal to c. |
xxxx01xx |
_SIDD_CMP_RANGES |
Find in ranges mode: For each character c in a, determine whether b0 <= c <= b1or b2 <= c <= b3… |
xxxx10xx |
_SIDD_CMP_EQUAL_EACH |
Find if equal each mode: This implements the string equality algorithm. |
xxxx11xx |
_SIDD_CMP_EQUAL_ORDERED |
Find if equal ordered mode: This implements the substring search algorithm. |
xxx0xxxx |
_SIDD_POSITIVE_POLARITY |
No effect. |
xx01xxxx |
_SIDD_NEGATIVE_POLARITY |
Negation of resulting bitmask. |
xx11xxxx |
_SIDD_MASKED_NEGATIVE_POLARITY |
Negation of resulting bitmask except for bits that have an index larger than the size of a or b (see details of pcmpstrm instruction). |
x0xxxxxx |
_SIDD_BIT_MASK |
The result mask is returned. |
x1xxxxxx |
_SIDD_UNIT_MASK |
Each bit of the result mask is expanded to 16 bytes or 8 words before it is returned. |
Before using this intrinsic, software must ensure that the processor supports the instruction.
Example
See the example for _mm_cmpistra.