# VPERMI2B — Full Permute of Bytes From Two Tables Overwriting the Index

Opcode/Instruction | Op/En | 64/32 bit Mode Support | CPUID Feature Flag | Description
--- | --- | --- | --- | ---
EVEX.128.66.0F38.W0 75 /r VPERMI2B xmm1 {k1}{z}, xmm2, xmm3/m128 | A | V/V | AVX512VL AVX512_VBMI | Permute bytes in xmm3/m128 and xmm2 using byte indexes in xmm1 and store the byte results in xmm1 using writemask k1.
EVEX.256.66.0F38.W0 75 /r VPERMI2B ymm1 {k1}{z}, ymm2, ymm3/m256 | A | V/V | AVX512VL AVX512_VBMI | Permute bytes in ymm3/m256 and ymm2 using byte indexes in ymm1 and store the byte results in ymm1 using writemask k1.
EVEX.512.66.0F38.W0 75 /r VPERMI2B zmm1 {k1}{z}, zmm2, zmm3/m512 | A | V/V | AVX512_VBMI | Permute bytes in zmm3/m512 and zmm2 using byte indexes in zmm1 and store the byte results in zmm1 using writemask k1.

## Instruction Operand Encoding ¶

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

### Description ¶

Permutes byte values in the second operand (the first source operand) and the third operand (the second source operand) using the byte indices in the first operand (the destination operand) to select byte elements from the second or third source operands. The selected byte elements are written to the destination at byte granularity under the writemask k1.

The first and second operands are ZMM/YMM/XMM registers. The first operand contains input indices to select elements from the two input tables in the 2nd and 3rd operands. The first operand is also the destination of the result. The third operand can be a ZMM/YMM/XMM register, or a 512/256/128-bit memory location. In each index byte, the id bit for table selection is bit 6/5/4, and bits [5:0]/[4:0]/[3:0] selects element within each input table.

Note that these instructions permit a byte value in the source operands to be copied to more than one location in the destination operand. Also, the same tables can be reused in subsequent iterations, but the index elements are overwritten.

Bits (MAX_VL-1:256/128) of the destination are zeroed for VL=256,128.

### Operation ¶

#### VPERMI2B (EVEX encoded versions) ¶

    (KL, VL) = (16, 128), (32, 256), (64, 512)
    IF VL = 128:
        id := 3;
    ELSE IF VL = 256:
        id := 4;
    ELSE IF VL = 512:
        id := 5;
    FI;
    TMP_DEST[VL-1:0] := DEST[VL-1:0];
    FOR j := 0 TO KL-1
        off := 8*SRC1[j*8 + id: j*8] ;
        IF k1[j] OR *no writemask*:
            DEST[j*8 + 7: j*8] := TMP_DEST[j*8+id+1]? SRC2[off+7:off] : SRC1[off+7:off];
        ELSE IF *zeroing-masking*
            DEST[j*8 + 7: j*8] := 0;
        *ELSE
            DEST[j*8 + 7: j*8] remains unchanged*
        FI;
    ENDFOR
    DEST[MAX_VL-1:VL] := 0;

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

    VPERMI2B __m512i _mm512_permutex2var_epi8(__m512i a, __m512i idx, __m512i b);

    VPERMI2B __m512i _mm512_mask2_permutex2var_epi8(__m512i a, __m512i idx, __mmask64 k, __m512i b);

    VPERMI2B __m512i _mm512_maskz_permutex2var_epi8(__mmask64 k, __m512i a, __m512i idx, __m512i b);

    VPERMI2B __m256i _mm256_permutex2var_epi8(__m256i a, __m256i idx, __m256i b);

    VPERMI2B __m256i _mm256_mask2_permutex2var_epi8(__m256i a, __m256i idx, __mmask32 k, __m256i b);

    VPERMI2B __m256i _mm256_maskz_permutex2var_epi8(__mmask32 k, __m256i a, __m256i idx, __m256i b);

    VPERMI2B __m128i _mm_permutex2var_epi8(__m128i a, __m128i idx, __m128i b);

    VPERMI2B __m128i _mm_mask2_permutex2var_epi8(__m128i a, __m128i idx, __mmask16 k, __m128i b);

    VPERMI2B __m128i _mm_maskz_permutex2var_epi8(__mmask16 k, __m128i a, __m128i idx, __m128i b);

### SIMD Floating-Point Exceptions ¶

None.

### Other Exceptions ¶

See Exceptions Type E4NF.nb in Table 2-50, “Type E4NF Class Exception Conditions.”