pmullw

Packed Multiply Low Word (MMX)

PMULLW mm, mm/m64

Multiplies 4 words and stores low 16 bits (MMX).

Details

Multiplies 4 word pairs in parallel and stores the low 16 bits of each product; the high 16 bits are discarded. This MMX instruction does not modify any EFLAGS and operates entirely within the 64-bit MMX register or memory operand.

Pseudocode Operation

for i = 0 to 3:
  product ← (signed16)dest[i*16+15:i*16] × (signed16)src[i*16+15:i*16]
  dest[i*16+15:i*16] ← product[15:0]

Example

PMULLW mm, mm/m64

Encoding

Binary Layout
0F
+0
D5
+1
 
Format MMX
Opcode NP 0F D5 /r1
Extension MMX

Operands

  • dest
    64-bit MMX register
  • src
    64-bit MMX register or Memory operand

Reference (Intel® SDM)

Instruction Forms

Opcode Instruction Op/En 64/32-bit Mode CPUID Description
66 0F D5 /r PMULLW xmm1, xmm2/m128 A V/V SSE2 Multiply the packed signed word integers in xmm1 and xmm2/m128, and store the low 16 bits of the results in xmm1.
VEX.128.66.0F.WIG D5 /r VPMULLW xmm1, xmm2, xmm3/m128 B V/V AVX Multiply the packed dword signed integers in xmm2 and xmm3/m128 and store the low 32 bits of each product in xmm1.
VEX.256.66.0F.WIG D5 /r VPMULLW ymm1, ymm2, ymm3/m256 B V/V AVX2 Multiply the packed signed word integers in ymm2 and ymm3/m256, and store the low 16 bits of the results in ymm1.
EVEX.128.66.0F.WIG D5 /r VPMULLW xmm1 {k1}{z}, xmm2, xmm3/m128 C V/V (AVX512VL AND AVX512BW) OR AVX10.1 Multiply the packed signed word integers in xmm2 and xmm3/m128, and store the low 16 bits of the results in xmm1 under writemask k1.
EVEX.256.66.0F.WIG D5 /r VPMULLW ymm1 {k1}{z}, ymm2, ymm3/m256 C V/V (AVX512VL AND AVX512BW) OR AVX10.1 Multiply the packed signed word integers in ymm2 and ymm3/m256, and store the low 16 bits of the results in ymm1 under writemask k1.
EVEX.512.66.0F.WIG D5 /r VPMULLW zmm1 {k1}{z}, zmm2, zmm3/m512 C V/V AVX512BW OR AVX10.1 Multiply the packed signed word integers in zmm2 and zmm3/m512, and store the low 16 bits of the results in zmm1 under writemask k1.

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 signed multiply of the packed signed word integers in the destination operand (first operand) and the source operand (second operand), and stores the low 16 bits of each intermediate 32-bit result in the destination operand. (Figure 4-12 shows this operation when using 64-bit 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 version 64-bit operand: The source operand can be an MMX technology register or a 64-bit memory location. The destination operand is 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 YMM destination register remain unchanged. PMULLW—Multiply Packed Signed Integers and Store Low Result Vol. 2B 4-391 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 destination YMM register are zeroed. VEX.L must be 0, otherwise the instruction will #UD. 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, a 512/256/128-bit memory location. The destination operand is conditionally updated based on writemask k1. SRC X3 X2 X1 X0 DEST Y3 Y2 Y1 Y0 TEMP Z3 = X3 ∗ Y3 Z2 = X2 ∗ Y2 Z1 = X1 ∗ Y1 Z0 = X0 ∗ Y0 DEST Z3[15:0] Z2[15:0] Z1[15:0] Z0[15:0] Figure 4-13. PMULLU Instruction Operation Using 64-bit Operands

Operation

PMULLW (With 64-bit Operands)
TEMP0[31:0] := DEST[15:0] ∗ SRC[15:0]; (* Signed multiplication *)
TEMP1[31:0] := DEST[31:16] ∗ SRC[31:16];
TEMP2[31:0] := DEST[47:32] ∗ SRC[47:32];
TEMP3[31:0] := DEST[63:48] ∗ SRC[63:48];
DEST[15:0] := TEMP0[15:0];
DEST[31:16] := TEMP1[15:0];
DEST[47:32] := TEMP2[15:0];
DEST[63:48] := TEMP3[15:0];

PMULLW (With 128-bit Operands)
TEMP0[31:0] := DEST[15:0] ∗ SRC[15:0]; (* Signed multiplication *)
TEMP1[31:0] := DEST[31:16] ∗ SRC[31:16];
TEMP2[31:0] := DEST[47:32] ∗ SRC[47:32];
TEMP3[31:0] := DEST[63:48] ∗ SRC[63:48];
TEMP4[31:0] := DEST[79:64] ∗ SRC[79:64];
TEMP5[31:0] := DEST[95:80] ∗ SRC[95:80];
TEMP6[31:0] := DEST[111:96] ∗ SRC[111:96];
TEMP7[31:0] := DEST[127:112] ∗ SRC[127:112];
DEST[15:0] := TEMP0[15:0];
DEST[31:16] := TEMP1[15:0];
DEST[47:32] := TEMP2[15:0];
DEST[63:48] := TEMP3[15:0];
DEST[79:64] := TEMP4[15:0];
DEST[95:80] := TEMP5[15:0];
DEST[111:96] := TEMP6[15:0];
DEST[127:112] := TEMP7[15:0];
DEST[MAXVL-1:256] := 0





PMULLW—Multiply Packed Signed Integers and Store Low Result                                                                               Vol. 2B 4-392
VPMULLW (VEX.128 Encoded Version)
Temp0[31:0] := SRC1[15:0] * SRC2[15:0]
Temp1[31:0] := SRC1[31:16] * SRC2[31:16]
Temp2[31:0] := SRC1[47:32] * SRC2[47:32]
Temp3[31:0] := SRC1[63:48] * SRC2[63:48]
Temp4[31:0] := SRC1[79:64] * SRC2[79:64]
Temp5[31:0] := SRC1[95:80] * SRC2[95:80]
Temp6[31:0] := SRC1[111:96] * SRC2[111:96]
Temp7[31:0] := SRC1[127:112] * SRC2[127:112]
DEST[15:0] := Temp0[15:0]
DEST[31:16] := Temp1[15:0]
DEST[47:32] := Temp2[15:0]
DEST[63:48] := Temp3[15:0]
DEST[79:64] := Temp4[15:0]
DEST[95:80] := Temp5[15:0]
DEST[111:96] := Temp6[15:0]
DEST[127:112] := Temp7[15:0]
DEST[MAXVL-1:128] := 0

PMULLW (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
temp[31:0] := SRC1[i+15:i] * SRC2[i+15:i]
DEST[i+15:i] := temp[15:0]
ELSE
IF *merging-masking*                                 ; merging-masking
THEN *DEST[i+15:i] remains unchanged*
ELSE *zeroing-masking*                            ; zeroing-masking
DEST[i+15:i] := 0
FI
FI;
ENDFOR
DEST[MAXVL-1:VL] := 0

Intel C/C++ Compiler Intrinsic Equivalent

VPMULLW __m512i _mm512_mullo_epi16(__m512i a, __m512i b);
VPMULLW __m512i _mm512_mask_mullo_epi16(__m512i s, __mmask32 k, __m512i a, __m512i b);
VPMULLW __m512i _mm512_maskz_mullo_epi16( __mmask32 k, __m512i a, __m512i b);
VPMULLW __m256i _mm256_mask_mullo_epi16(__m256i s, __mmask16 k, __m256i a, __m256i b);
VPMULLW __m256i _mm256_maskz_mullo_epi16( __mmask16 k, __m256i a, __m256i b);
VPMULLW __m128i _mm_mask_mullo_epi16(__m128i s, __mmask8 k, __m128i a, __m128i b);
VPMULLW __m128i _mm_maskz_mullo_epi16( __mmask8 k, __m128i a, __m128i b);
PMULLW __m64 _mm_mullo_pi16(__m64 m1, __m64 m2)
(V)PMULLW __m128i _mm_mullo_epi16 ( __m128i a, __m128i b)
VPMULLW __m256i _mm256_mullo_epi16 ( __m256i a, __m256i b);

Flags Affected

None. PMULLW—Multiply Packed Signed Integers and Store Low Result Vol. 2B 4-393

Exceptions

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 2-51, “Type E4 Class Exception Conditions.” PMULLW—Multiply Packed Signed Integers and Store Low Result Vol. 2B 4-394