<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Jan 11, 2013, at 11:47 AM, Justin Holewinski <<a href="mailto:justin.holewinski@gmail.com">justin.holewinski@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span style="font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; display: inline !important; float: none; ">Out of curiosity, what is the use-case for isFMAFasterThanMulAndAdd? If a target declares that FMA is actually slower for a given type, why not just declare it as illegal for that type? Wouldn't that accomplish the same thing without another target hook? I feel like I'm missing something here.</span></blockquote></div><br><div>FMA is not semantically equivalent to fmul+fadd. If the user called the fma() libm function, we're obligated to translate that into an actual FMA instruction (or a libcall). If they were fmul+fadd with FP_CONTRACT turned on, we're allowed to generate an FMA, but we don't want to if it will be slower than just doing the fmul+fadd.</div><div><br></div><div>--Owen</div></body></html>