On October 31, 2015 6:17:35 PM GMT+01:00, Eric Botcazou <ebotca...@adacore.com> wrote: >> Lets go with this patch and hopefully stabilize the tree. I don't >think the >> vector conversions represent an important case. > >Unfortunately the patch introduces GIMPLE checking failures in Ada so >it will >need to be completed/improved. But let's postpone it because we have >another >class of GIMPLE checking failures introduced by the >useless_type_conversion_p >change itself: > >c37213j.adb:21:05: warning: variable "X" is read but never assigned >c37213j.adb: In function 'C37213J.PROC.CONSTPROP': >c37213j.adb:41:4: error: invalid conversion in gimple call >struct c37213j__proc__value___PAD > >struct c37213j__proc__value___PAD > ># .MEM_38 = VDEF <.MEM_37> >MEM[(struct c37213j__proc__value___PAD *)R.12_25] = c37213j.proc.value >(); >[static-chain: &FRAME.39] [return slot optimization] > >and: > >eric@polaris:~/build/gcc/native> ~/install/gnat-head/bin/gcc -S >c37213j.adb - >O2 >c37213j.adb:21:05: warning: variable "X" is read but never assigned >c37213j.adb: In function 'C37213J.PROC.VALUE': >c37213j.adb:26:5: error: invalid conversion in return statement >struct c37213j__proc__value___PAD > >struct c37213j__proc__value___PAD > ># VUSE <.MEM_11> >return _9(D); > >What happens here is that GIMPLE statements are remapped through >cloning and >we have a variably-modified type returned by a nested function, so the >type of >the LHS of a GIMPLE_CALL or that of the RHS of a GIMPLE_RETURN is >remapped but >of course not the return type of the function. This used to be OK >because >remapping is done by means of copy_node and preserves TYPE_CANONICAL, >so the >conversion between remapped and original type was deemed useless; now >the >TYPE_CANONICAL check is gone so the conversion is not useless >anymore... > >I don't think that we want to introduce an artificial VCE to fix this >so we >probably need a couple of kludges in the GIMPLE verifier instead. > >In any case, the more I look into the fallout of the >useless_type_conversion_p >change, the more I find it ill-advised. We used to have a solid type >system >in the middle-end by means of the predicate and now we have cases for >which it >ought to return false and returns true (e.g. non-structurally >equivalent types >with different calling conventions) and cases for which it can return >true and >returns false (remapped types or types deemed equivalent by the >languages). >I don't really know what it was made for, but there must be a better >way...
I suggest to re-instantiate the canonical type checks for the aggregate type case. And add all these test cases. Richard. > > * gnat.dg/discr45.adb: New test.
