VPMULTISHIFTQB

Select Packed Unaligned Bytes From Quadword Sources

stableVMJITAOTinstruction

Encodings

Operand encoding

Each mode is a value of the Op/En column above. It says which field of the encoded instruction carries each operand, in the order they are written, and whether the instruction reads it, writes it or both.

Measured cost

Description#

This instruction selects eight unaligned bytes from each input qword element of the second source operand (the third operand) and writes eight assembled bytes for each qword element in the destination operand (the first operand). Each byte result is selected using a byte-granular shift control within the corresponding qword element of the first source operand (the second operand). Each byte result in the destination operand is updated under the writemask k1.

Only the low 6 bits of each control byte are used to select an 8-bit slot to extract the output byte from the qword data in the second source operand. The starting bit of the 8-bit slot can be unaligned relative to any byte boundary and is extracted from the input qword source at the location specified in the low 6-bit of the control byte. If the 8-bit slot would exceed the qword boundary, the out-of-bound portion of the 8-bit slot is wrapped back to start from bit 0 of the input qword element.

The first source 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 64-bit memory location. The destination operand is a ZMM/YMM/XMM register.

Operation#

VPMULTISHIFTQB DEST, SRC1, SRC2 (EVEX encoded version)
(KL, VL) = (2, 128),(4, 256), (8, 512)
FOR i := 0 TO KL-1

    IF EVEX.b=1 AND src2 is memory THEN
                tcur := src2.qword[0]; //broadcasting

    ELSE
                tcur := src2.qword[i];

    FI;
    FOR j := 0 to 7

          ctrl := src1.qword[i].byte[j] & 63;
          FOR k := 0 to 7

                res.bit[k] := tcur.bit[ (ctrl+k) mod 64 ];
          ENDFOR
          IF k1[i*8+j] or no writemask THEN

                DEST.qword[i].byte[j] := res;
          ELSE IF zeroing-masking THEN

                DEST.qword[i].byte[j] := 0;
    ENDFOR
ENDFOR
DEST.qword[MAX_VL-1:VL] := 0;

Intel C/C++ compiler intrinsics#

VPMULTISHIFTQB __m512i _mm512_multishift_epi64_epi8( __m512i a, __m512i b);
VPMULTISHIFTQB __m512i _mm512_mask_multishift_epi64_epi8(__m512i s, __mmask64 k, __m512i a, __m512i b);
VPMULTISHIFTQB __m512i _mm512_maskz_multishift_epi64_epi8( __mmask64 k, __m512i a, __m512i b);
VPMULTISHIFTQB __m256i _mm256_multishift_epi64_epi8( __m256i a, __m256i b);
VPMULTISHIFTQB __m256i _mm256_mask_multishift_epi64_epi8(__m256i s, __mmask32 k, __m256i a, __m256i b);
VPMULTISHIFTQB __m256i _mm256_maskz_multishift_epi64_epi8( __mmask32 k, __m256i a, __m256i b);
VPMULTISHIFTQB __m128i _mm_multishift_epi64_epi8( __m128i a, __m128i b);
VPMULTISHIFTQB __m128i _mm_mask_multishift_epi64_epi8(__m128i s, __mmask8 k, __m128i a, __m128i b);
VPMULTISHIFTQB __m128i _mm_maskz_multishift_epi64_epi8( __mmask8 k, __m128i a, __m128i b);

SIMD Floating-Point Exceptions#

None.

Other Exceptions#

See Table 2-52, "Type E4NF Class Exception Conditions."

Sources

• This instruction in the Intel manual
• Latency and throughput per microarchitecture