x86 Instruction Set Reference

# PMULLW

# Multiply Packed Signed Integers and Store Low Result

Opcode Mnemonic Description
0F D5 /r PMULLW mm, mm/m64 Multiply the packed signed word integers in mm1 register and mm2/m64, and store the low 16 bits of the results in mm1.
66 0F D5 /r PMULLW xmm1, xmm2/m128 Multiply the packed signed word integers in xmm1 and xmm2/m128, and store the low 16 bits of the results in xmm1.

# Description

Performs an 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 4-3 shows this operation when using 64-bit operands.) The source operand can be an MMX technology register or a 64-bit memory location, or it can be an XMM register or a 128-bit memory location. The destination operand can be an MMX technology register or an XMM register.

# Operation

if(OperandSize == 64) {
	//PMULLW instruction with 64-bit operands:
	//Signed multiplication
	Temporary0[0..31] = Destination[0..15] * Source[0..15];
	Temporary1[0..31] = Destination[16..31] * Source[16..31];
	Temporary2[0..31] = Destination[32..47] * Source[32..47];
	Temporary3[0..31] = Destination[48..63] * Source[48..63];
	Destination[0..15] = Temporary0[0..15];
	Destination[16..31] = Temporary1[0..15];
	Destination[32..47] = Temporary2[0..15];
	Destination[48..63] = Temporary3[0..15];
}
else {
	//PMULLW instruction with 64-bit operands:
	//Signed multiplication
	Temporary0[0..31] = Destination[0..15] * Source[0..15];
	Temporary1[0..31] = Destination[16..31] * Source[16..31];
	Temporary2[0..31] = Destination[32..47] * Source[32..47];
	Temporary3[0..31] = Destination[48..63] * Source[48..63];
	Temporary4[0..31] = Destination[64..79] * Source[64..79];
	Temporary5[0..31] = Destination[80..95] * Source[80..95];
	Temporary6[0..31] = Destination[96..111] * Source[96..111];
	Temporary7[0..31] = Destination[112..127] * Source[112..127];
	Destination[0..15] = Temporary0[0..15];
	Destination[16..31] = Temporary1[0..15];
	Destination[32..47] = Temporary2[0..15];
	Destination[48..63] = Temporary3[0..15];
	Destination[64..79] = Temporary4[0..15];
	Destination[80..95] = Temporary5[0..15];
	Destination[96..111] = Temporary6[0..15];
	Destination[112..127] = Temporary7[0..15];
}
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# Flags affected

None.

Instruction Latency Throughput Execution Unit
CPUID 0F3n/0F2n/069n 0F3n/0F2n/069n 0F2n
PMULLW mm, mm 9/8/- 1/1/- FP_MUL
PMULLW xmm, xmm 9/8/3+1 2/2/2 FP_MUL

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