# PCMPEQB/PCMPEQW/PCMPEQD — Compare Packed Data for Equal

Opcode/Instruction | Op/ En | 64/32 bit Mode Support | CPUID Feature Flag | 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 AVX512F | 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 AVX512F | 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 | 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 AVX512BW | 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.
EVEX.256.66.0F.WIG 74 /r VPCMPEQB k1 {k2}, ymm2, ymm3 /m256 | D | V/V | AVX512VL AVX512BW | 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 | 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 AVX512BW | 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 AVX512BW | 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 | 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.

> 1. See note in Section 2.5, “Intel® AVX and Intel® SSE Instruction Exception Classification,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A, and Section 23.25.3, “Exception Conditions of Legacy SIMD Instructions Operating on MMX Registers,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3B.

## 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.

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)

### 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

### 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
    DEST[MAX_KL-1:KL] := 0

## Intel C/C++ Compiler Intrinsic Equivalents ¶

    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.

## 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 2-49, “Type E4 Class Exception Conditions.”

EVEX-encoded VPCMPEQB/W, see Exceptions Type E4.nb in Table 2-49, “Type E4 Class Exception Conditions.”