<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Jan 7, 2021, at 5:26 PM, Philip Reames via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="Singleton"><blockquote type="cite" cite="mid:CACs=ty+KD-K73UcxPxJh64xRiFheAr03dRay-cF0hPXyV_Z3WQ@mail.gmail.com" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><div dir="ltr" class=""><div class="">If you want to avoid verifier changes, the token type already gives you what you want: it is opaque, cannot be loaded and stored or phid, and can serve as a "value multiplexer". You could invent new intrinsics to extract the values you need. The source of a token cannot be obscured, so lowering can always look through a token operand, find the source, and link up the correct SDValue in codegen. The downside is that all this solution would be opaque to the mid-level optimizers. They already understand insertvalue and extractvalue. So, I don't think this is a good way to go, but it's worth considering.</div><div class=""><br class=""></div><div class="">I think, if we all agree that first class aggregates that can be loaded, stored, and phi'd, were a historical design mistake, then your original proposed solution is a step in the direction of removing FCA support.</div><div class=""><br class=""></div><div class="">I wonder if, in the future, it would be possible to auto-upgrade IR that contains these FCA operations by splitting them into scalar operations, and we could make the verifier reject all of these undesired operations.</div></div></blockquote><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">+1 to this goal. Getting there might be tricky, and take a while, but definite +1 to the direction. <span class="Apple-converted-space"> </span></span></div></div></blockquote></div><br class=""><div class="">Yeah I agree with Phillip, this would be a great direction.</div><div class=""><br class=""></div><div class="">-Chris</div></body></html>