PCMPISTRM (Packed Compare Implicit Length Strings, Return Mask)

Opcodes

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description
66 0F 3A 62 /r imm8 PCMPISTRM xmm1, xmm2/m128, imm8 RM V/V SSE4_2 Perform a packed comparison of string data with implicit lengths, generating a mask, and storing the result in XMM0.
VEX.128.66.0F3A.WIG 62 /r ib VPCMPISTRM xmm1, xmm2/m128, imm8 RM V/V AVX Perform a packed comparison of string data with implicit lengths, generating a Mask, and storing the result in XMM0.

Instruction Operand Encoding

Op/En Operand 1 Operand 2 Operand 3 Operand 4
RM ModRM:reg (r) ModRM:r/m (r) imm8 NA

Description

The instruction compares data from two strings based on the encoded value in the imm8 byte (see Section 4.1, “Imm8 Control Byte Operation for PCMPESTRI / PCMPESTRM / PCMPISTRI / PCMPISTRM”) generating a mask stored to XMM0.

Each string is represented by a single value. The value is an xmm (or possibly m128 for the second operand) which contains the data elements of the string (byte or word data). Each input byte/word is augmented with a valid/invalid tag. A byte/word is considered valid only if it has a lower index than the least significant null byte/word. (The least significant null byte/word is also considered invalid.)

The comparison and aggregation operation are performed according to the encoded value of Imm8 bit fields (see Section 4.1). As defined by imm8[6], IntRes2 is then either stored to the least significant bits of XMM0 (zero extended to 128 bits) or expanded into a byte/word-mask and then stored to XMM0.

Note that the Arithmetic Flags are written in a non-standard manner in order to supply the most relevant informa-tion:

CFlag – Reset if IntRes2 is equal to zero, set otherwise

ZFlag – Set if any byte/word of xmm2/mem128 is null, reset otherwise

SFlag – Set if any byte/word of xmm1 is null, reset otherwise

OFlag – IntRes2[0]

AFlag – Reset

PFlag – Reset

Note: In VEX.128 encoded versions, bits (VLMAX-1:128) of XMM0 are zeroed. VEX.vvvv is reserved and must be 1111b, VEX.L must be 0, otherwise the instruction will #UD.

Effective Operand Size

Operating mode/size Operand1 Operand 2 Result
16 bit xmm xmm/m128 XMM0
32 bit xmm xmm/m128 XMM0
64 bit xmm xmm/m128 XMM0
64 bit + REX.W xmm xmm/m128 XMM0

Intel C/C++ Compiler Intrinsic Equivalent For Returning Mask

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

Intel C/C++ Compiler Intrinsics For Reading EFlag Results

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

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

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

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

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

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Exceptions Type 4; additionally, this instruction does not cause #GP if the memory operand is not aligned to 16 Byte boundary, and

#UD If VEX.L = 1. If VEX.vvvv ≠ 1111B.