HADDPD—Packed Double-FP Horizontal AddInstruction Operand EncodingDescriptionAdds the double-precision floating-point values in the high and low quadwords of the destination operand and stores the result in the low quadword of the destination operand. Adds the double-precision floating-point values in the high and low quadwords of the source operand and stores the result in the high quadword of the destination operand. In 64-bit mode, use of the REX.R prefix permits this instruction to access additional registers (XMM8-XMM15).See Figure3-16 for HADDPD; see Figure3-17 for VHADDPD.Opcode/InstructionOp/ En64/32-bit ModeCPUID Feature FlagDescription66 0F 7C /rHADDPD xmm1,xmm2/m128RMV/VSSE3Horizontal add packed double-precision floating-point values from xmm2/m128 to xmm1.VEX.128.66.0F.WIG 7C /rVHADDPD xmm1,xmm2, xmm3/m128RVMV/VAVXHorizontal add packed double-precision floating-point values from xmm2 and xmm3/mem.VEX.256.66.0F.WIG 7C /rVHADDPD ymm1, ymm2, ymm3/m256RVMV/VAVXHorizontal add packed double-precision floating-point values from ymm2 and ymm3/mem.Op/EnOperand 1Operand 2Operand 3Operand 4RMModRM:reg (r, w)ModRM:r/m (r)NANARVMModRM:reg (w)VEX.vvvv (r)ModRM:r/m (r)NAFigure 3-16. HADDPD—Packed Double-FP Horizontal AddOM15993HADDPD xmm1, xmm2/m128xmm1xmm2/m128[63:0][127:64][127:64][63:0][63:0][127:64]Result:xmm1xmm2/m128[63:0] +xmm2/m128[127:64]xmm1[63:0] + xmm1[127:64]
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