[PATCH, MPX, 2/X] Pointers Checker [7/25] Suppress BUILT_IN_CHKP_ARG_BND optimizations.

[Jeff Law]

On 11/05/13 05:02, Ilya Enkovich wrote:
>
> If I just set abnormal phi flag for SSA_NAME, SSA verifier should fail
> because it does not used in abnormal phi, shouldn't it?
Well, we can also change the verifier to not fail when it finds that 
flag set on a pointer when bounds checking is enabled.


   Also it would
> prevent all optimizations for these SSA_NAMEs right?  Instrumentation
> is performed on the earlier stage, right after we build SSA. I think
> using abnormal phi flag and binding pointers with bounds via calls
> would prevent some useful optimizations.
It certainly prevents some optimizations, but it's main purpose is to 
avoid certain copy propagation and coalescing.  If you don't set that 
flag, there's probably all kinds places you're going to have to hack up 
to keep the properties you desire for bounded pointers.

I would rather be a bit conservative and miss some optimizations by 
setting SSA_NAME_OCCURS_IN_ABNORMAL_PHI than be continually hacking up 
passes to special case bounded pointers.  We can obviously revisit this 
decision later.

Jeff