_mm_cmpistri

Artikel
11/16/2012

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
);

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

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.

Requirements

Intrinsic	Architecture
_mm_cmpistri	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 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.

Example

See the example for _mm_cmpistra.

Change History

Date	History	Reason
July 2008	Revised the constant names.	Content bug fix.

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