[llvm-commits] patch: teach deadargelim to work on externally visible functions!

[Chris Lattner]

On Jan 10, 2010, at 7:56 PM, Rafael Espindola wrote:

>> This example has undefined behavior, so it doesn't matter what we
>> produce.  We should just always generate the faster code.  This sounds
>> like a pretty serious performance bug on ELF systems.
> 
> On the ELF standard maybe :-(
> Functions that are not marked with hidden/protected visibility can be
> overridden at runtime.  That is used for thing like changing malloc by
> using LD_PRELOAD.

Treating the functions like that would be completely impractical.  This would disable IP constant prop and many other interprocedural optimizations.  If you want that behavior, we should introduce a new attribute, which results in us generating a new "strong but overridable" linkage type.  Sorta like a non-ODR "external".

-Chris