# PMAXUB/PMAXUW — Maximum of Packed Unsigned Integers

Opcode/Instruction | Op / En | 64/32 bit Mode Support | CPUID Feature Flag | Description
--- | --- | --- | --- | ---
NP 0F DE /r1 PMAXUB mm1, mm2/m64 | A | V/V | SSE | Compare unsigned byte integers in mm2/m64 and mm1 and returns maximum values.
66 0F DE /r PMAXUB xmm1, xmm2/m128 | A | V/V | SSE2 | Compare packed unsigned byte integers in xmm1 and xmm2/m128 and store packed maximum values in xmm1.
66 0F 38 3E/r PMAXUW xmm1, xmm2/m128 | A | V/V | SSE4_1 | Compare packed unsigned word integers in xmm2/m128 and xmm1 and stores maximum packed values in xmm1.
VEX.128.66.0F DE /r VPMAXUB xmm1, xmm2, xmm3/m128 | B | V/V | AVX | Compare packed unsigned byte integers in xmm2 and xmm3/m128 and store packed maximum values in xmm1.
VEX.128.66.0F38 3E/r VPMAXUW xmm1, xmm2, xmm3/m128 | B | V/V | AVX | Compare packed unsigned word integers in xmm3/m128 and xmm2 and store maximum packed values in xmm1.
VEX.256.66.0F DE /r VPMAXUB ymm1, ymm2, ymm3/m256 | B | V/V | AVX2 | Compare packed unsigned byte integers in ymm2 and ymm3/m256 and store packed maximum values in ymm1.
VEX.256.66.0F38 3E/r VPMAXUW ymm1, ymm2, ymm3/m256 | B | V/V | AVX2 | Compare packed unsigned word integers in ymm3/m256 and ymm2 and store maximum packed values in ymm1.
EVEX.128.66.0F.WIG DE /r VPMAXUB xmm1{k1}{z}, xmm2, xmm3/m128 | C | V/V | AVX512VL AVX512BW | Compare packed unsigned byte integers in xmm2 and xmm3/m128 and store packed maximum values in xmm1 under writemask k1.
EVEX.256.66.0F.WIG DE /r VPMAXUB ymm1{k1}{z}, ymm2, ymm3/m256 | C | V/V | AVX512VL AVX512BW | Compare packed unsigned byte integers in ymm2 and ymm3/m256 and store packed maximum values in ymm1 under writemask k1.
EVEX.512.66.0F.WIG DE /r VPMAXUB zmm1{k1}{z}, zmm2, zmm3/m512 | C | V/V | AVX512BW | Compare packed unsigned byte integers in zmm2 and zmm3/m512 and store packed maximum values in zmm1 under writemask k1.
EVEX.128.66.0F38.WIG 3E /r VPMAXUW xmm1{k1}{z}, xmm2, xmm3/m128 | C | V/V | AVX512VL AVX512BW | Compare packed unsigned word integers in xmm2 and xmm3/m128 and store packed maximum values in xmm1 under writemask k1.
EVEX.256.66.0F38.WIG 3E /r VPMAXUW ymm1{k1}{z}, ymm2, ymm3/m256 | C | V/V | AVX512VL AVX512BW | Compare packed unsigned word integers in ymm2 and ymm3/m256 and store packed maximum values in ymm1 under writemask k1.
EVEX.512.66.0F38.WIG 3E /r VPMAXUW zmm1{k1}{z}, zmm2, zmm3/m512 | C | V/V | AVX512BW | Compare packed unsigned word integers in zmm2 and zmm3/m512 and store packed maximum values in zmm1 under writemask k1.

> 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 Mem | ModRM:reg (w) | EVEX.vvvv (r) | ModRM:r/m (r) | N/A

## Description ¶

Performs a SIMD compare of the packed unsigned byte, word integers in the second source operand and the first source operand and returns the maximum value for each pair of integers to the destination operand.

Legacy SSE version PMAXUB: 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 first source and destination operands are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (MAXVL-1:128) of the corresponding destination register remain unchanged.

VEX.128 encoded version: The first source and destination operands are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (MAXVL-1:128) of the corresponding destination register are zeroed.

VEX.256 encoded version: The second source operand can be an YMM register or a 256-bit memory location. The first source and destination operands are YMM registers.

EVEX encoded versions: The first source operand is a ZMM/YMM/XMM register; The second source operand is a ZMM/YMM/XMM register or a 512/256/128-bit memory location. The destination operand is conditionally updated based on writemask k1.

## Operation ¶

### PMAXUB (64-bit Operands) ¶

    IF DEST[7:0] > SRC[17:0]) THEN
        DEST[7:0] := DEST[7:0];
    ELSE
        DEST[7:0] := SRC[7:0]; FI;
    (* Repeat operation for 2nd through 7th bytes in source and destination operands *)
    IF DEST[63:56] > SRC[63:56]) THEN
        DEST[63:56] := DEST[63:56];
    ELSE
        DEST[63:56] := SRC[63:56]; FI;

### PMAXUB (128-bit Legacy SSE Version) ¶

        IF DEST[7:0] >SRC[7:0] THEN
            DEST[7:0] := DEST[7:0];
        ELSE
            DEST[15:0] := SRC[7:0]; FI;
        (* Repeat operation for 2nd through 15th bytes in source and destination operands *)
        IF DEST[127:120] >SRC[127:120] THEN
            DEST[127:120] := DEST[127:120];
        ELSE
            DEST[127:120] := SRC[127:120]; FI;
    DEST[MAXVL-1:128] (Unmodified)

### VPMAXUB (VEX.128 Encoded Version) ¶

        IF SRC1[7:0] >SRC2[7:0] THEN
            DEST[7:0] := SRC1[7:0];
        ELSE
            DEST[7:0] := SRC2[7:0]; FI;
        (* Repeat operation for 2nd through 15th bytes in source and destination operands *)
        IF SRC1[127:120] >SRC2[127:120] THEN
            DEST[127:120] := SRC1[127:120];
        ELSE
            DEST[127:120] := SRC2[127:120]; FI;
    DEST[MAXVL-1:128] := 0

### VPMAXUB (VEX.256 Encoded Version) ¶

        IF SRC1[7:0] >SRC2[7:0] THEN
            DEST[7:0] := SRC1[7:0];
        ELSE
            DEST[15:0] := SRC2[7:0]; FI;
        (* Repeat operation for 2nd through 31st bytes in source and destination operands *)
        IF SRC1[255:248] >SRC2[255:248] THEN
            DEST[255:248] := SRC1[255:248];
        ELSE
            DEST[255:248] := SRC2[255:248]; FI;
    DEST[MAXVL-1:128] := 0

### VPMAXUB (EVEX Encoded Versions) ¶

    (KL, VL) = (16, 128), (32, 256), (64, 512)
    FOR j := 0 TO KL-1
        i := j * 8
        IF k1[j] OR *no writemask* THEN
            IF SRC1[i+7:i] > SRC2[i+7:i]
                THEN DEST[i+7:i] := SRC1[i+7:i];
                ELSE DEST[i+7:i] := SRC2[i+7:i];
            FI;
            ELSE
                IF *merging-masking*
                    THEN *DEST[i+7:i] remains unchanged*
                    ELSE ; zeroing-masking
                        DEST[i+7:i] := 0
                FI
        FI;
    ENDFOR;
    DEST[MAXVL-1:VL] := 0

### PMAXUW (128-bit Legacy SSE Version) ¶

        IF DEST[15:0] >SRC[15:0] THEN
            DEST[15:0] := DEST[15:0];
        ELSE
            DEST[15:0] := SRC[15:0]; FI;
        (* Repeat operation for 2nd through 7th words in source and destination operands *)
        IF DEST[127:112] >SRC[127:112] THEN
            DEST[127:112] := DEST[127:112];
        ELSE
            DEST[127:112] := SRC[127:112]; FI;
    DEST[MAXVL-1:128] (Unmodified)

### VPMAXUW (VEX.128 Encoded Version) ¶

        IF SRC1[15:0] > SRC2[15:0] THEN
            DEST[15:0] := SRC1[15:0];
        ELSE
            DEST[15:0] := SRC2[15:0]; FI;
        (* Repeat operation for 2nd through 7th words in source and destination operands *)
        IF SRC1[127:112] >SRC2[127:112] THEN
            DEST[127:112] := SRC1[127:112];
        ELSE
            DEST[127:112] := SRC2[127:112]; FI;
    DEST[MAXVL-1:128] := 0

### VPMAXUW (VEX.256 Encoded Version) ¶

        IF SRC1[15:0] > SRC2[15:0] THEN
            DEST[15:0] := SRC1[15:0];
        ELSE
            DEST[15:0] := SRC2[15:0]; FI;
        (* Repeat operation for 2nd through 15th words in source and destination operands *)
        IF SRC1[255:240] >SRC2[255:240] THEN
            DEST[255:240] := SRC1[255:240];
        ELSE
            DEST[255:240] := SRC2[255:240]; FI;
    DEST[MAXVL-1:128] := 0

### VPMAXUW (EVEX Encoded Versions) ¶

    (KL, VL) = (8, 128), (16, 256), (32, 512)
    FOR j := 0 TO KL-1
        i := j * 16
        IF k1[j] OR *no writemask* THEN
            IF SRC1[i+15:i] > SRC2[i+15:i]
                THEN DEST[i+15:i] := SRC1[i+15:i];
                ELSE DEST[i+15:i] := SRC2[i+15:i];
            FI;
            ELSE
                IF *merging-masking*
                    THEN *DEST[i+15:i] remains unchanged*
                    ELSE ; zeroing-masking
                        DEST[i+15:i] := 0
                FI
        FI;
    ENDFOR;
    DEST[MAXVL-1:VL] := 0

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

    VPMAXUB __m512i _mm512_max_epu8( __m512i a, __m512i b);

    VPMAXUB __m512i _mm512_mask_max_epu8(__m512i s, __mmask64 k, __m512i a, __m512i b);

    VPMAXUB __m512i _mm512_maskz_max_epu8( __mmask64 k, __m512i a, __m512i b);

    VPMAXUW __m512i _mm512_max_epu16( __m512i a, __m512i b);

    VPMAXUW __m512i _mm512_mask_max_epu16(__m512i s, __mmask32 k, __m512i a, __m512i b);

    VPMAXUW __m512i _mm512_maskz_max_epu16( __mmask32 k, __m512i a, __m512i b);

    VPMAXUB __m256i _mm256_mask_max_epu8(__m256i s, __mmask32 k, __m256i a, __m256i b);

    VPMAXUB __m256i _mm256_maskz_max_epu8( __mmask32 k, __m256i a, __m256i b);

    VPMAXUW __m256i _mm256_mask_max_epu16(__m256i s, __mmask16 k, __m256i a, __m256i b);

    VPMAXUW __m256i _mm256_maskz_max_epu16( __mmask16 k, __m256i a, __m256i b);

    VPMAXUB __m128i _mm_mask_max_epu8(__m128i s, __mmask16 k, __m128i a, __m128i b);

    VPMAXUB __m128i _mm_maskz_max_epu8( __mmask16 k, __m128i a, __m128i b);

    VPMAXUW __m128i _mm_mask_max_epu16(__m128i s, __mmask8 k, __m128i a, __m128i b);

    VPMAXUW __m128i _mm_maskz_max_epu16( __mmask8 k, __m128i a, __m128i b);

    (V)PMAXUB __m128i _mm_max_epu8 ( __m128i a, __m128i b);

    (V)PMAXUW __m128i _mm_max_epu16 ( __m128i a, __m128i b)

    VPMAXUB __m256i _mm256_max_epu8 ( __m256i a, __m256i b);

    VPMAXUW __m256i _mm256_max_epu16 ( __m256i a, __m256i b);

    PMAXUB __m64 _mm_max_pu8(__m64 a, __m64 b);

## SIMD Floating-Point Exceptions ¶

None.

## Other Exceptions ¶

Non-EVEX-encoded instruction, see Table 2-21, “Type 4 Class Exception Conditions.”

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