pcmpeqw

Packed Compare Equal Word

PCMPEQW xmm, xmm/m128

Compares words for equality.

Details

Performs a packed comparison for equality on 16-bit word elements. For each word position, the result is 0xFFFF if the elements are equal, or 0x0000 if they are not equal. No traditional flags are affected; results are stored in the destination register. Available in SSE2 and later; operates on 128-bit vectors (eight 16-bit elements).

Pseudocode Operation

for i ← 0 to 7 do
  if dest.word[i] == src.word[i] then
    dest.word[i] ← 0xFFFF
  else
    dest.word[i] ← 0x0000
  end if
end for

Example

PCMPEQW xmm0, xmm1

Encoding

Binary Layout
66
+0
0F
+1
75
+2
 
Format SSE2
Opcode 66 0F 75
Extension SSE2

Operands

  • dest
    128-bit SSE/AVX register (XMM)
  • src
    128-bit XMM register or 128-bit memory

Reference (Intel® SDM)

Instruction Forms

Opcode Instruction Op/En 64/32-bit Mode CPUID Description
NP 0F 74 /r1 PCMPEQB mm, mm/m64 A V/V MMX Compare packed bytes in mm/m64 and mm for equality.
66 0F 74 /r PCMPEQB xmm1, xmm2/m128 A V/V SSE2 Compare packed bytes in xmm2/m128 and xmm1 for equality.
NP 0F 75 /r1 PCMPEQW mm, mm/m64 A V/V MMX Compare packed words in mm/m64 and mm for equality.
66 0F 75 /r PCMPEQW xmm1, xmm2/m128 A V/V SSE2 Compare packed words in xmm2/m128 and xmm1 for equality.
NP 0F 76 /r1 PCMPEQD mm, mm/m64 A V/V MMX Compare packed doublewords in mm/m64 and mm for equality.
66 0F 76 /r PCMPEQD xmm1, xmm2/m128 A V/V SSE2 Compare packed doublewords in xmm2/m128 and xmm1 for equality.
VEX.128.66.0F.WIG 74 /r VPCMPEQB xmm1, xmm2, xmm3/m128 B V/V AVX Compare packed bytes in xmm3/m128 and xmm2 for equality.
VEX.128.66.0F.WIG 75 /r VPCMPEQW xmm1, xmm2, xmm3/m128 B V/V AVX Compare packed words in xmm3/m128 and xmm2 for equality.
VEX.128.66.0F.WIG 76 /r VPCMPEQD xmm1, xmm2, xmm3/m128 B V/V AVX Compare packed doublewords in xmm3/m128 and xmm2 for equality.
VEX.256.66.0F.WIG 74 /r VPCMPEQB ymm1, ymm2, ymm3 /m256 B V/V AVX2 Compare packed bytes in ymm3/m256 and ymm2 for equality.
VEX.256.66.0F.WIG 75 /r VPCMPEQW ymm1, ymm2, ymm3 /m256 B V/V AVX2 Compare packed words in ymm3/m256 and ymm2 for equality.
VEX.256.66.0F.WIG 76 /r VPCMPEQD ymm1, ymm2, ymm3 /m256 B V/V AVX2 Compare packed doublewords in ymm3/m256 and ymm2 for equality.
EVEX.128.66.0F.W0 76 /r VPCMPEQD k1 {k2}, xmm2, xmm3/m128/m32bcst C V/V (AVX512VL AND AVX512F) OR AVX10.1 Compare Equal between int32 vector xmm2 and int32 vector xmm3/m128/m32bcst, and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask.
EVEX.256.66.0F.W0 76 /r VPCMPEQD k1 {k2}, ymm2, ymm3/m256/m32bcst C V/V (AVX512VL AND AVX512F) OR AVX10.1 Compare Equal between int32 vector ymm2 and int32 vector ymm3/m256/m32bcst, and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask.
EVEX.512.66.0F.W0 76 /r VPCMPEQD k1 {k2}, zmm2, zmm3/m512/m32bcst C V/V AVX512F OR AVX10.1 Compare Equal between int32 vectors in zmm2 and zmm3/m512/m32bcst, and set destination k1 according to the comparison results under writemask k2.
EVEX.128.66.0F.WIG 74 /r VPCMPEQB k1 {k2}, xmm2, xmm3 /m128 D V/V (AVX512VL AND AVX512BW) OR AVX10.1 Compare packed bytes in xmm3/m128 and xmm2 for equality and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask. PCMPEQB/PCMPEQW/PCMPEQD— Compare Packed Data for Equal Vol. 2B 4-245 Opcode/ Op/ En 64/32 bit CPUID Feature Description Instruction Mode Flag Support
EVEX.256.66.0F.WIG 74 /r VPCMPEQB k1 {k2}, ymm2, ymm3 /m256 D V/V (AVX512VL AND AVX512BW) OR AVX10.1 Compare packed bytes in ymm3/m256 and ymm2 for equality and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask.
EVEX.512.66.0F.WIG 74 /r VPCMPEQB k1 {k2}, zmm2, zmm3 /m512 D V/V AVX512BW OR AVX10.1 Compare packed bytes in zmm3/m512 and zmm2 for equality and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask.
EVEX.128.66.0F.WIG 75 /r VPCMPEQW k1 {k2}, xmm2, xmm3 /m128 D V/V (AVX512VL AND AVX512BW) OR AVX10.1 Compare packed words in xmm3/m128 and xmm2 for equality and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask.
EVEX.256.66.0F.WIG 75 /r VPCMPEQW k1 {k2}, ymm2, ymm3 /m256 D V/V (AVX512VL AND AVX512BW) OR AVX10.1 Compare packed words in ymm3/m256 and ymm2 for equality and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask.
EVEX.512.66.0F.WIG 75 /r VPCMPEQW k1 {k2}, zmm2, zmm3 /m512 D V/V AVX512BW OR AVX10.1 Compare packed words in zmm3/m512 and zmm2 for equality and set vector mask k1 to reflect the zero/nonzero status of each element of the result, under writemask.

Instruction Operand Encoding

Op/En Tuple Type Operand 1 Operand 2 Operand 3 Operand 4
A N/A ModRM:reg (r, w) ModRM:r/m (r) N/A N/A
B N/A ModRM:reg (w) VEX.vvvv (r) ModRM:r/m (r) N/A
C Full ModRM:reg (w) EVEX.vvvv (r) ModRM:r/m (r) N/A
D Full Mem ModRM:reg (w) EVEX.vvvv (r) ModRM:r/m (r) N/A

Description

Performs a SIMD compare for equality of the packed bytes, words, or doublewords in the destination operand (first operand) and the source operand (second operand). If a pair of data elements is equal, the corresponding data element in the destination operand is set to all 1s; otherwise, it is set to all 0s. The (V)PCMPEQB instruction compares the corresponding bytes in the destination and source operands; the (V)PCMPEQW instruction compares the corresponding words in the destination and source operands; and the (V)PCMPEQD instruction compares the corresponding doublewords in the destination and source operands. In 64-bit mode and not encoded with VEX/EVEX, using a REX prefix in the form of REX.R permits this instruction to access additional registers (XMM8-XMM15). Legacy SSE instructions: The source operand can be an MMX technology register or a 64-bit memory location. The destination operand can be an MMX technology register. 128-bit Legacy SSE version: The second source operand can be an XMM register or a 128-bit memory location. The first source and destination operands are XMM registers. Bits (MAXVL-1:128) of the corresponding YMM destination register remain unchanged. PCMPEQB/PCMPEQW/PCMPEQD— Compare Packed Data for Equal Vol. 2B 4-246 VEX.128 encoded version: The second source operand can be an XMM register or a 128-bit memory location. The first source and destination operands are XMM registers. Bits (MAXVL-1:128) of the corresponding YMM register are zeroed. VEX.256 encoded version: The first source operand is a YMM register. The second source operand is a YMM register or a 256-bit memory location. The destination operand is a YMM register. EVEX encoded VPCMPEQD: The first source operand (second operand) is a ZMM/YMM/XMM register. The second source operand can be a ZMM/YMM/XMM register, a 512/256/128-bit memory location or a 512/256/128-bit vector broadcasted from a 32-bit memory location. The destination operand (first operand) is a mask register updated according to the writemask k2. EVEX encoded VPCMPEQB/W: The first source operand (second operand) is a ZMM/YMM/XMM register. The second source operand can be a ZMM/YMM/XMM register, a 512/256/128-bit memory location. The destination operand (first operand) is a mask register updated according to the writemask k2.

Operation

PCMPEQB (With 64-bit Operands)
IF DEST[7:0] = SRC[7:0]
THEN DEST[7:0) := FFH;
ELSE DEST[7:0] := 0; FI;
(* Continue comparison of 2nd through 7th bytes in DEST and SRC *)
IF DEST[63:56] = SRC[63:56]
THEN DEST[63:56] := FFH;
ELSE DEST[63:56] := 0; FI;

COMPARE_BYTES_EQUAL (SRC1, SRC2)
IF SRC1[7:0] = SRC2[7:0]
THEN DEST[7:0] := FFH;
ELSE DEST[7:0] := 0; FI;
(* Continue comparison of 2nd through 15th bytes in SRC1 and SRC2 *)
IF SRC1[127:120] = SRC2[127:120]
THEN DEST[127:120] := FFH;
ELSE DEST[127:120] := 0; FI;

COMPARE_WORDS_EQUAL (SRC1, SRC2)
IF SRC1[15:0] = SRC2[15:0]
THEN DEST[15:0] := FFFFH;
ELSE DEST[15:0] := 0; FI;
(* Continue comparison of 2nd through 7th 16-bit words in SRC1 and SRC2 *)
IF SRC1[127:112] = SRC2[127:112]
THEN DEST[127:112] := FFFFH;
ELSE DEST[127:112] := 0; FI;

COMPARE_DWORDS_EQUAL (SRC1, SRC2)
IF SRC1[31:0] = SRC2[31:0]
THEN DEST[31:0] := FFFFFFFFH;
ELSE DEST[31:0] := 0; FI;
(* Continue comparison of 2nd through 3rd 32-bit dwords in SRC1 and SRC2 *)
IF SRC1[127:96] = SRC2[127:96]
THEN DEST[127:96] := FFFFFFFFH;
ELSE DEST[127:96] := 0; FI;

PCMPEQB (With 128-bit Operands)
DEST[127:0] := COMPARE_BYTES_EQUAL(DEST[127:0],SRC[127:0])
DEST[MAXVL-1:128] (Unmodified)


PCMPEQB/PCMPEQW/PCMPEQD— Compare Packed Data for Equal                                                                              Vol. 2B 4-247
VPCMPEQB (VEX.128 Encoded Version)
DEST[127:0] := COMPARE_BYTES_EQUAL(SRC1[127:0],SRC2[127:0])
DEST[MAXVL-1:128] := 0

VPCMPEQB (VEX.256 Encoded Version)
DEST[127:0] := COMPARE_BYTES_EQUAL(SRC1[127:0],SRC2[127:0])
DEST[255:128] := COMPARE_BYTES_EQUAL(SRC1[255:128],SRC2[255:128])
DEST[MAXVL-1:256] := 0

VPCMPEQB (EVEX Encoded Versions)
(KL, VL) = (16, 128), (32, 256), (64, 512)

FOR j := 0 TO KL-1
i := j * 8
IF k2[j] OR *no writemask*
THEN
/* signed comparison */
CMP := SRC1[i+7:i] == SRC2[i+7:i];
IF CMP = TRUE
THEN DEST[j] := 1;
ELSE DEST[j] := 0; FI;
ELSE    DEST[j] := 0                                  ; zeroing-masking onlyFI;
FI;
ENDFOR
DEST[MAX_KL-1:KL] := 0

PCMPEQW (With 64-bit Operands)
IF DEST[15:0] = SRC[15:0]
THEN DEST[15:0] := FFFFH;
ELSE DEST[15:0] := 0; FI;
(* Continue comparison of 2nd and 3rd words in DEST and SRC *)
IF DEST[63:48] = SRC[63:48]
THEN DEST[63:48] := FFFFH;
ELSE DEST[63:48] := 0; FI;

PCMPEQW (With 128-bit Operands)
DEST[127:0] := COMPARE_WORDS_EQUAL(DEST[127:0],SRC[127:0])
DEST[MAXVL-1:128] (Unmodified)

VPCMPEQW (VEX.128 Encoded Version)
DEST[127:0] := COMPARE_WORDS_EQUAL(SRC1[127:0],SRC2[127:0])
DEST[MAXVL-1:128] := 0

VPCMPEQW (VEX.256 Encoded Version)
DEST[127:0] := COMPARE_WORDS_EQUAL(SRC1[127:0],SRC2[127:0])
DEST[255:128] := COMPARE_WORDS_EQUAL(SRC1[255:128],SRC2[255:128])
DEST[MAXVL-1:256] := 0





PCMPEQB/PCMPEQW/PCMPEQD— Compare Packed Data for Equal                                                                              Vol. 2B 4-248
VPCMPEQW (EVEX Encoded Versions)
(KL, VL) = (8, 128), (16, 256), (32, 512)
FOR j := 0 TO KL-1
i := j * 16
IF k2[j] OR *no writemask*
THEN
/* signed comparison */
CMP := SRC1[i+15:i] == SRC2[i+15:i];
IF CMP = TRUE
THEN DEST[j] := 1;
ELSE DEST[j] := 0; FI;
ELSE    DEST[j] := 0                                  ; zeroing-masking onlyFI;
FI;
ENDFOR
DEST[MAX_KL-1:KL] := 0

PCMPEQD (With 64-bit Operands)
IF DEST[31:0] = SRC[31:0]
THEN DEST[31:0] := FFFFFFFFH;
ELSE DEST[31:0] := 0; FI;
IF DEST[63:32] = SRC[63:32]
THEN DEST[63:32] := FFFFFFFFH;
ELSE DEST[63:32] := 0; FI;

PCMPEQD (With 128-bit Operands)
DEST[127:0] := COMPARE_DWORDS_EQUAL(DEST[127:0],SRC[127:0])
DEST[MAXVL-1:128] (Unmodified)

VPCMPEQD (VEX.128 Encoded Version)
DEST[127:0] := COMPARE_DWORDS_EQUAL(SRC1[127:0],SRC2[127:0])
DEST[MAXVL-1:128] := 0

VPCMPEQD (VEX.256 Encoded Version)
DEST[127:0] := COMPARE_DWORDS_EQUAL(SRC1[127:0],SRC2[127:0])
DEST[255:128] := COMPARE_DWORDS_EQUAL(SRC1[255:128],SRC2[255:128])
DEST[MAXVL-1:256] := 0

VPCMPEQD (EVEX Encoded Versions)
(KL, VL) = (4, 128), (8, 256), (16, 512)
FOR j := 0 TO KL-1
i := j * 32
IF k2[j] OR *no writemask*
THEN
/* signed comparison */
IF (EVEX.b = 1) AND (SRC2 *is memory*)
THEN CMP := SRC1[i+31:i] = SRC2[31:0];
ELSE CMP := SRC1[i+31:i] = SRC2[i+31:i];
FI;
IF CMP = TRUE
THEN DEST[j] := 1;
ELSE DEST[j] := 0; FI;
ELSE    DEST[j] := 0                                  ; zeroing-masking only
FI;
ENDFOR


PCMPEQB/PCMPEQW/PCMPEQD— Compare Packed Data for Equal                                                                              Vol. 2B 4-249
DEST[MAX_KL-1:KL] := 0

Intel C/C++ Compiler Intrinsic Equivalent

VPCMPEQB __mmask64 _mm512_cmpeq_epi8_mask(__m512i a, __m512i b);
VPCMPEQB __mmask64 _mm512_mask_cmpeq_epi8_mask(__mmask64 k, __m512i a, __m512i b);
VPCMPEQB __mmask32 _mm256_cmpeq_epi8_mask(__m256i a, __m256i b);
VPCMPEQB __mmask32 _mm256_mask_cmpeq_epi8_mask(__mmask32 k, __m256i a, __m256i b);
VPCMPEQB __mmask16 _mm_cmpeq_epi8_mask(__m128i a, __m128i b);
VPCMPEQB __mmask16 _mm_mask_cmpeq_epi8_mask(__mmask16 k, __m128i a, __m128i b);
VPCMPEQW __mmask32 _mm512_cmpeq_epi16_mask(__m512i a, __m512i b);
VPCMPEQW __mmask32 _mm512_mask_cmpeq_epi16_mask(__mmask32 k, __m512i a, __m512i b);
VPCMPEQW __mmask16 _mm256_cmpeq_epi16_mask(__m256i a, __m256i b);
VPCMPEQW __mmask16 _mm256_mask_cmpeq_epi16_mask(__mmask16 k, __m256i a, __m256i b);
VPCMPEQW __mmask8 _mm_cmpeq_epi16_mask(__m128i a, __m128i b);
VPCMPEQW __mmask8 _mm_mask_cmpeq_epi16_mask(__mmask8 k, __m128i a, __m128i b);
VPCMPEQD __mmask16 _mm512_cmpeq_epi32_mask( __m512i a, __m512i b);
VPCMPEQD __mmask16 _mm512_mask_cmpeq_epi32_mask(__mmask16 k, __m512i a, __m512i b);
VPCMPEQD __mmask8 _mm256_cmpeq_epi32_mask(__m256i a, __m256i b);
VPCMPEQD __mmask8 _mm256_mask_cmpeq_epi32_mask(__mmask8 k, __m256i a, __m256i b);
VPCMPEQD __mmask8 _mm_cmpeq_epi32_mask(__m128i a, __m128i b);
VPCMPEQD __mmask8 _mm_mask_cmpeq_epi32_mask(__mmask8 k, __m128i a, __m128i b);
PCMPEQB __m64 _mm_cmpeq_pi8 (__m64 m1, __m64 m2)
PCMPEQW __m64 _mm_cmpeq_pi16 (__m64 m1, __m64 m2)
PCMPEQD __m64 _mm_cmpeq_pi32 (__m64 m1, __m64 m2)
(V)PCMPEQB __m128i _mm_cmpeq_epi8 ( __m128i a, __m128i b)
(V)PCMPEQW __m128i _mm_cmpeq_epi16 ( __m128i a, __m128i b)
(V)PCMPEQD __m128i _mm_cmpeq_epi32 ( __m128i a, __m128i b)
VPCMPEQB __m256i _mm256_cmpeq_epi8 ( __m256i a, __m256i b)
VPCMPEQW __m256i _mm256_cmpeq_epi16 ( __m256i a, __m256i b)
VPCMPEQD __m256i _mm256_cmpeq_epi32 ( __m256i a, __m256i b)

Flags Affected

None.

Exceptions

SIMD Floating-Point Exceptions

None.

Other Exceptions

Non-EVEX-encoded instruction, see Table 2-21, “Type 4 Class Exception Conditions.” EVEX-encoded VPCMPEQD, see Table 2-51, “Type E4 Class Exception Conditions.” EVEX-encoded VPCMPEQB/W, see Exceptions Type E4.nb in Table 2-51, “Type E4 Class Exception Conditions.” PCMPEQB/PCMPEQW/PCMPEQD— Compare Packed Data for Equal Vol. 2B 4-250