truction to be executed atomically.</p>
<p>In 64-bit mode, the instruction’s default operation size is 32 bits. Using a REX prefix in the form of REX.R permits access to additional registers (R8-R15). Using a REX prefix in the form of REX.W promotes operation to 64 bits. See the summary chart at the beginning of this section for encoding data and limits.</p>
<h2>Operation</h2>
<pre>DEST ← (DEST – (SRC + CF));</pre>
<h2>Intel C/C++ Compiler Intrinsic Equivalent</h2>
<p>SBB:</p>
<p>extern unsigned char 