explain how work pcmpestri

align 16 s1 db "This is a string!ss",0 s2 db "This is a string!ss",0 Call CmpStrings invoke ExitProcess,0 proc CmpStrings mov eax, s2 mov edx, s1 StringCMP: sub eax, edx sub edx, 16 strcmpLoop: add edx, 16 movups xmm0, [edx] pcmpistri xmm0, [edx+eax],0011000b ja strcmpLoop jc strcmpDiff invoke MessageBox,0,"Text !","Found !",0 sub eax, eax ret strcmpDiff: invoke MessageBox,0,"Text","Not found",0 ret endp

Check out this link:
http://www.strchr.com/strcmp_and_strlen_using_sse_4.2

This section describes what you want:
Equal ordered (imm[3:2] = 11). Substring search (strstr). The first operand contains a string to search for, the second is a string to search in. The bit mask includes 1 if the substring is found at the corresponding position:

operand2 = "WhenWeWillBeWed!", operand1 = "We"
IntRes1 = 000010000000100

There's also code posted to do just that:

Code:

; compile with FASM
; Immediate byte constants
EQUAL_ANY           = 0000b
RANGES              = 0100b
EQUAL_EACH          = 1000b
EQUAL_ORDERED       = 1100b
NEGATIVE_POLARITY = 010000b
BYTE_MASK        = 1000000b

; ==== strstr ====
strstr_sse42:
  ; ecx = haystack, edx = needle

  push esi
  push edi
  MovDqU xmm2, dqword[edx] ; load the first 16 bytes of neddle
  Pxor xmm3, xmm3
  lea eax, [ecx - 16]

  ; find the first possible match of 16-byte fragment in haystack
STRSTR_MAIN_LOOP:
    add eax, 16
    PcmpIstrI xmm2, dqword[eax], EQUAL_ORDERED
    ja STRSTR_MAIN_LOOP

  jnc STRSTR_NOT_FOUND

  add eax, ecx ; save the possible match start
  mov edi, edx
  mov esi, eax
  sub edi, esi
  sub esi, 16

  ; compare the strings
@@:
    add esi, 16
    MovDqU    xmm1, dqword[esi + edi]
    ; mask out invalid bytes in the haystack
    PcmpIstrM xmm3, xmm1, EQUAL_EACH + NEGATIVE_POLARITY + BYTE_MASK
    MovDqU xmm4, dqword[esi]
    PAnd xmm4, xmm0
    PcmpIstrI xmm1, xmm4, EQUAL_EACH + NEGATIVE_POLARITY
    ja @B

  jnc STRSTR_FOUND

  ; continue searching from the next byte
  sub eax, 15
  jmp STRSTR_MAIN_LOOP

STRSTR_NOT_FOUND:
  xor eax, eax

STRSTR_FOUND:
  pop edi
  pop esi
  ret