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sem_prag.adb (Process_Atomic_Shared_Volatile): Propagate atomicity from an object to its underlying type only if it is composite. 

* sem_prag.adb (Process_Atomic_Shared_Volatile): Propagate
	atomicity from an object to its underlying type only if it
	is composite.

From-SVN: r187555
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Eric Botcazou 2012-05-15 20:08:00 +00:00 committed by Eric Botcazou
parent e13240d148
commit 8ba9905de6
2 changed files with 21 additions and 2 deletions
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6
gcc/ada/ChangeLog
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@ -1,3 +1,9 @@
2012-05-15 Eric Botcazou <ebotcazou@adacore.com>
* sem_prag.adb (Process_Atomic_Shared_Volatile): Propagate
atomicity from an object to its underlying type only if it
is composite.
2012-05-06 Pascal Obry <obry@adacore.com>
Revert

17
gcc/ada/sem_prag.adb
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@ -2972,16 +2972,29 @@ package body Sem_Prag is
Set_Has_Delayed_Freeze (E);
end if;
-- An interesting improvement here. If an object of type X is
-- declared atomic, and the type X is not atomic, that's a
-- An interesting improvement here. If an object of composite
-- type X is declared atomic, and the type X isn't, that's a
-- pity, since it may not have appropriate alignment etc. We
-- can rescue this in the special case where the object and
-- type are in the same unit by just setting the type as
-- atomic, so that the back end will process it as atomic.
-- Note: we used to do this for elementary types as well,
-- but that turns out to be a bad idea and can have unwanted
-- effects, most notably if the type is elementary, the object
-- a simple component within a record, and both are in a spec:
-- every object of this type in the entire program will be
-- treated as atomic, thus incurring a potentially costly
-- synchronization operation for every access.
-- Of course it would be best if the back end could just adjust
-- the alignment etc for the specific object, but that's not
-- something we are capable of doing at this point.
Utyp := Underlying_Type (Etype (E));
if Present (Utyp)
and then Is_Composite_Type (Utyp)
and then Sloc (E) > No_Location
and then Sloc (Utyp) > No_Location
and then