-point values in the high and low quadwords of the source operand and stores the result in the high quadword of the destination operand.</p>
<p>In 64-bit mode, use of the REX.R prefix permits this instruction to access additional registers (XMM8-XMM15).</p>
<p>See <a href="./HADDPD.html#fig-3-16">Figure 3-16</a> for HADDPD; see <a href="./HADDPD.html#fig-3-17">Figure 3-17</a> for VHADDPD.</p>
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