<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Just as an FYI: I am going to push this patch forward. I need this in the near term and to quote the great zygoloid:<div><br></div><div><zygoloid> gottesmm: if you want it done soon, feel free to take over that <br> patch and run with it<br><zygoloid> gottesmm: (otherwise i'll circle back to it in the great blue <br> eventually...)</div><div><br></div><div>Michael</div><div><br><div><div>On May 20, 2013, at 8:03 AM, Chris Lattner <<a href="mailto:clattner@apple.com">clattner@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">On May 16, 2013, at 12:36 PM, Richard Smith <<a href="mailto:richard@metafoo.co.uk">richard@metafoo.co.uk</a>> wrote:<br><blockquote type="cite"><br><br>Since it would probably help to quantify the complexity increase, I've implemented my more recent suggestion (patch attached). This patch allows 'nobuiltin' on a function declaration or definition, and adds a 'builtin' attribute which can only be present on a call site for a direct call to a function declared with the 'nobuiltin' attribute. The 'builtin' attribute has the effect of canceling out the 'nobuiltin' attribute on the declaration.<br></blockquote><br>Ok. Please make "hasFnAttr(Attribute::NoBuiltin)" abort though: it will be a common bug to call this instead of your new accessor.<br><br><blockquote type="cite">This (incidentally) also exactly matches what we want for another Clang feature: we want a -fno-builtin-foo which makes 'foo' not be a builtin (but we still want __builtin_foo to have the builtin behavior). This, again, is not possible with the existing 'nobuiltin' attribute, due to the function pointer problem. Instead, Clang currently just provides -fno-builtin, and even *that* only provides a broken half-implementation -- it calls TargetLibraryInfo::disableAllFunctions, whose effect is not preserved across "clang -fno-builtin -emit-llvm | opt", nor across LTO.<br></blockquote><br>There are several problems in this space. While your new attribute may be useful to help in this area, it is definitely not sufficient to solve the problem. -fno-builtin-strlen should disable transformations from strchr->strlen (as a random example) even if there is no LLVM IR function for strlen.<br><br>-Chris<br><br><br>_______________________________________________<br>LLVM Developers mailing list<br><a href="mailto:LLVMdev@cs.uiuc.edu">LLVMdev@cs.uiuc.edu</a><span class="Apple-converted-space"> </span> <a href="http://llvm.cs.uiuc.edu/">http://llvm.cs.uiuc.edu</a><br><a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev</a></div></blockquote></div><br></div></body></html>