ada: Extend expansion delaying mechanism to conditional expressions

When an aggregate that needs to be converted into a series of assignments is
present in an expression of a parent aggregate, or in the expression of an
allocator, an object declaration, or an assignment in very specific cases,
its expansion is delayed until its parent itself is expanded.  This makes
it possible to avoid creating a superfluous temporary for the aggregate.

This change extends the delaying mechanism in the case of record aggregates
to intermediate conditional expressions, that is to say, to the conditional
expressions that are present between the parent and the aggregate, provided
that the aggregate be a dependent expression, directly or recursively.  This
again makes it possible to avoid creating a temporary for the aggregate.

gcc/ada/

	* exp_aggr.ads (Is_Delayed_Conditional_Expression): New predicate.
	* exp_aggr.adb (Convert_To_Assignments.Known_Size): Likewise.
	(Convert_To_Assignments): Climb the parent chain, looking through
	qualified expressions and dependent expressions of conditional
	expressions, to find out whether the expansion may be delayed.
	Call Known_Size for this in the case of an object declaration.
	If so, set Expansion_Delayed on the aggregate as well as all the
	intermediate conditional expressions.
	(Initialize_Component): Reset the Analyzed flag on an initialization
	expression that is a conditional expression whose expansion has been
	delayed.
	(Is_Delayed_Conditional_Expression): New predicate.
	* exp_ch3.adb (Expand_N_Object_Declaration): Handle initialization
	expressions that are conditional expressions whose expansion has
	been delayed.
	* exp_ch4.adb (Build_Explicit_Assignment): New procedure.
	(Expand_Allocator_Expression): Handle initialization expressions
	that are conditional expressions whose expansion has been delayed.
	(Expand_N_Case_Expression): Deal with expressions whose expansion
	has been delayed by waiting for the rewriting of their parent as
	an assignment statement and then optimizing the assignment.
	(Expand_N_If_Expression): Likewise.
	(Expand_N_Qualified_Expression): Do not apply a predicate check to
	an operand that is a delayed aggregate or conditional expression.
	* gen_il-gen-gen_nodes.adb (N_If_Expression): Add Expansion_Delayed
	semantic flag.
	(N_Case_Expression): Likewise.
	* sinfo.ads (Expansion_Delayed): Document extended usage.

1 files changed, 4 insertions, 0 deletions

diff --git a/gcc/ada/exp_aggr.ads b/gcc/ada/exp_aggr.ads
index a9eb051..17fa38b 100644
--- a/gcc/ada/exp_aggr.ads
+++ b/gcc/ada/exp_aggr.ads
@@ -54,6 +54,10 @@ package Exp_Aggr is
    --  Returns True if N is an aggregate of some kind whose Expansion_Delayed
    --  flag is set (see sinfo for meaning of flag).
 
+   function Is_Delayed_Conditional_Expression (N : Node_Id) return Boolean;
+   --  Returns True if N is a conditional expression whose Expansion_Delayed
+   --  flag is set (see sinfo for meaning of flag).
+
    function Static_Array_Aggregate (N : Node_Id) return Boolean;
    --  N is an array aggregate that may have a component association with
    --  an others clause and a range. If bounds are static and the expressions