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_mm_cmpistri

Microsoft Specific

Emits the Streaming SIMD Extensions 4 (SSE4) instruction pcmpistri. This instruction compares two parameters.

int _mm_cmpistri (
   __m128i a, 
   __m128i b, 
   const int mode
); 

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.

An integer between 0 and Maxsize. MaxSize when the computed mask equals 0. Otherwise, the index of the leftmost or rightmost bit set to 1 in this mask. A bit in mode determines whether the leftmost or rightmost index is returned.

The pcmpistri instruction computes the bitmask, where bit0, bit1, bit2… in the mask correspond to the result of the operation on a0, a1, a2… in a.

Intrinsic

Architecture

_mm_cmpistri

x86, x64

Header file <nmmintrin.h>

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 table:

mode in binary

Defined 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 pcmpstri instruction).

x0xxxxxx

_SIDD_LEAST_SIGNIFICANT

Index of the rightmost bit set to 1 in the resulting mask is returned.

x1xxxxxx

_SIDD_MOST_SIGNIFICANT

Index of the leftmost bit set to 1 in the resulting mask is returned.

Before using this intrinsic, software must ensure that the processor supports the instruction.

See the example for _mm_cmpistra.

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