[PATCH] D66217: [BuildLibCalls] Noalias annotation

[Dávid Bolvanský via Phabricator via llvm-commits]

xbolva00 marked an inline comment as done.
xbolva00 added inline comments.


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Comment at: lib/Transforms/Utils/BuildLibCalls.cpp:263
     Changed |= setDoesNotCapture(F, 0);
+    Changed |= setDoesNotAlias(F, 0);
     Changed |= setDoesNotCapture(F, 1);
----------------
jdoerfert wrote:
> xbolva00 wrote:
> > jdoerfert wrote:
> > > I'm not sure what this means or what this is going to help, but maybe I just miss something.
> > Target buffer may not overlap with other args.
> > 
> > I can remove it, but some future optimizations based on noalias info would be weaker.
> I was wrong, if that is the `sprintf` semantics, keep it.
Yea :)

man sprintf

Some programs imprudently rely on code such as the following

           sprintf(buf, "%s some further text", buf);

       to append text to buf.  However, the standards explicitly note that the
       results are undefined if source and destination  buffers  overlap  when
       calling  sprintf(), snprintf(), vsprintf(), and vsnprintf()...



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  https://reviews.llvm.org/D66217/new/

https://reviews.llvm.org/D66217