On Thu, Jun 20, 2013 at 2:39 PM, Michael Gottesman <[email protected]>wrote:
> > On Jun 20, 2013, at 2:16 PM, Eli Friedman <[email protected]> wrote: > > On Tue, Jun 18, 2013 at 3:11 PM, Michael Gottesman <[email protected]> > wrote: > >> Hello cfe commits! >> >> The attached patch adds checked-arithmetic builtins to ameliorate such >> code in security critical applications (for instance webkit). It simply >> exposes {u,s}{add,sub,mul}. >> >> *NOTE* The u{add,sub} overlaps with the multi precision built-ins. I >> decided to add in the additional builtin since users are going to see >> s{add,sub} and look for u{add,sub}. We could add in a Builtins.h header >> where I could implement the checked arithmetic with the multi precision >> arithmetic builtins but I felt that was a bigger change than this. >> >> > It looks like you copy-pasted some stuff you didn't mean to in the changes > to LanguageExtensions.rst. > > > = /. Fixed. > > > + return RValue::get(Builder.CreateZExt(Carry, X->getType())); > > These builtins all return bool, right? Why are you zero-extending here? > (You might be able to get away with this in C because of integer > promotions, but I'm pretty sure it'll explode in C++.) > > > = /. Fixed. The reason I was zero extending was that I was basing this off > of the multiprecision builtin code and forgot to remove it. > > > IIRC, we don't actually support CodeGen of llvm.smul.with.overflow with > 64-bit operands on x86-32; it would be nice to print a proper error message > instead of crashing. (At least, we didn't at one point; I don't recall if > it ever got fixed.) > > > I just codegened my test file on OS X with -arch i386 and it codegened > fine. So it looks like it was fixed. > > Hows this look: > LGTM. -Eli
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