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[Ada] Expand renamings of subcomponents of an atomic or VFA object

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2019-12-16  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* exp_ch8.adb (Expand_N_Object_Renaming_Declaration): Document
	third special case of renamings requiring special handling.
	(Evaluation_Required): Return true for an atomic or VFA prefix.

From-SVN: r279423
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Eric Botcazou 2019-12-16 10:33:59 +00:00 committed by Pierre-Marie de Rodat
parent 90393d3ca7
commit 9c9535f974
2 changed files with 25 additions and 5 deletions
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6
gcc/ada/ChangeLog
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@ -1,3 +1,9 @@
2019-12-16 Eric Botcazou <ebotcazou@adacore.com>
* exp_ch8.adb (Expand_N_Object_Renaming_Declaration): Document
third special case of renamings requiring special handling.
(Evaluation_Required): Return true for an atomic or VFA prefix.
2019-12-16 Ed Schonberg <schonberg@adacore.com>
* checks.adb (Apply_Float_Conversion_Check): Use node of type

24
gcc/ada/exp_ch8.adb
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@ -72,7 +72,14 @@ package body Exp_Ch8 is
-- clause applies (that can specify an arbitrary bit boundary), or where
-- the enclosing record itself has a non-standard representation.
-- In these two cases, we pre-evaluate the renaming expression, by
-- In Ada 2020, a third case arises when the renamed object is a nonatomic
-- subcomponent of an atomic object, because reads of or writes to it must
-- access the enclosing atomic object. That's also the case for an object
-- subject to the Volatile_Full_Access GNAT aspect/pragma in any language
-- version. For the sake of simplicity, we treat any subcomponent of an
-- atomic or Volatile_Full_Access object in any language version this way.
-- In these three cases, we pre-evaluate the renaming expression, by
-- extracting and freezing the values of any subscripts, and then we
-- set the flag Is_Renaming_Of_Object which means that any reference
-- to the object will be handled by macro substitution in the front
@ -102,10 +109,10 @@ package body Exp_Ch8 is
-- Determines whether it is necessary to do static name evaluation for
-- renaming of Nam. It is considered necessary if evaluating the name
-- involves indexing a packed array, or extracting a component of a
-- record to which a component clause applies. Note that we are only
-- interested in these operations if they occur as part of the name
-- itself, subscripts are just values that are computed as part of the
-- evaluation, so their form is unimportant.
-- record to which a component clause applies, or a subcomponent of an
-- atomic object. Note that we are only interested in these operations
-- if they occur as part of the name itself, subscripts are just values
-- that are computed as part of the evaluation, so they are unimportant.
-- In addition, always return True for Modify_Tree_For_C since the
-- code generator doesn't know how to handle renamings.
@ -121,6 +128,10 @@ package body Exp_Ch8 is
elsif Nkind_In (Nam, N_Indexed_Component, N_Slice) then
if Is_Packed (Etype (Prefix (Nam))) then
return True;
elsif Is_Atomic_Or_VFA_Object (Prefix (Nam)) then
return True;
else
return Evaluation_Required (Prefix (Nam));
end if;
@ -141,6 +152,9 @@ package body Exp_Ch8 is
then
return True;
elsif Is_Atomic_Or_VFA_Object (Prefix (Nam)) then
return True;
else
return Evaluation_Required (Prefix (Nam));
end if;