PATCH RFA: PR 29286: Handle placement new aliasing issues

[Eric Botcazou]

> But we do nothing to add call clobbered variables or tags, only the
> things it would otherwise reference if not for TBAA (which is not the
> same set).

Interesting.  I added the call clobbered variables business for T_R_C_A_A 
because assignment of addresses of variables to such pointers effectively 
causes them to "escape", which is turn causes them to be marked as call 
clobbered by the tree aliasing engine.  So the circle needed to be closed.

Looks like T_R_C_A_A could be "lowered" to CHANGE_DYNAMIC_TYPE_EXPRs then, 
making it less heavyweight and ultimately private to the Ada compiler, which 
I guess would not displease anyone. :-)

-- 
Eric Botcazou