[Ada] Unnesting: do not generate push/pop for exceptions

2018-05-29  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_ch6.adb (Expand_N_Subprogram_Body): Do not generate push/pop for
	exceptions if subprogram unnesting is in effect, because these branch
	nodes are relevant only in the presence of nested subprograms.

From-SVN: r260883

gcc/ada/ChangeLog

 2018-05-29  Ed Schonberg  <schonberg@adacore.com>
 
+	* exp_ch6.adb (Expand_N_Subprogram_Body): Do not generate push/pop for
+	exceptions if subprogram unnesting is in effect, because these branch
+	nodes are relevant only in the presence of nested subprograms.
+
+2018-05-29  Ed Schonberg  <schonberg@adacore.com>
+
 	* libgnat/s-fatgen.adb (Succ, Pred):  Raise Constraint_Error
 	unconditionally when applied to the largest positive (resp. largest
 	negative) value of a floating-point type.

gcc/ada/exp_ch6.adb

@@ -5664,12 +5664,16 @@ package body Exp_Ch6 is
       --  If local-exception-to-goto optimization active, insert dummy push
       --  statements at start, and dummy pop statements at end, but inhibit
       --  this if we have No_Exception_Handlers, since they are useless and
-      --  intefere with analysis, e.g. by codepeer.
+      --  interfere with analysis, e.g. by CodePeer. We also don't need these
+      --  if we're unnesting subprograms because the only purpose of these
+      --  nodes is to ensure we don't set a label in one subprogram and branch
+      --  to it in another.
 
       if (Debug_Flag_Dot_G
            or else Restriction_Active (No_Exception_Propagation))
         and then not Restriction_Active (No_Exception_Handlers)
         and then not CodePeer_Mode
+        and then not Unnest_Subprogram_Mode
         and then Is_Non_Empty_List (L)
       then
          declare