Presumably, Apple is relying on SSE for floating point, like x86-64 does. <i>That</i> certainly is both faster and simpler than dealing with the bizarre x87.<p>And you don't have to insert extra code at all call sites. You can assume that <i>your</i> stack is correctly aligned at entry too, so if you just make your stack frame a multiple of 16 bytes, you'll be fine.