[Ada] Unnesting: avoid unnecessary loads of System

2018-10-09  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_unst.adb (Unnest_Subprogram): Do not load System to obtain
	the Address entity unless an activation record is being built.
	Removes useless with_clauses for System when nested subprograms
	do not have uplevel references, and therefore do not need
	activation records.

From-SVN: r264967

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index e7ce7ee15dfddb87a22ac7680e8350df22de66de..aee5a62c0f41294609ae1ce32cbf441a615ffdf9 100644 (file)
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,11 @@
+2018-10-09  Ed Schonberg  <schonberg@adacore.com>
+
+       * exp_unst.adb (Unnest_Subprogram): Do not load System to obtain
+       the Address entity unless an activation record is being built.
+       Removes useless with_clauses for System when nested subprograms
+       do not have uplevel references, and therefore do not need
+       activation records.
+
 2018-10-09  Ed Schonberg  <schonberg@adacore.com>
 
        * sem_ch6.adb (Fully_Conformant_Expressions): Handle properly

diff --git a/gcc/ada/exp_unst.adb b/gcc/ada/exp_unst.adb
index de4ea1a26ce27f0d3e6cfe43a0c7c95c9340abe8..0b63aa66fc59de535e130ab096f74d18f8d01b91 100644 (file)
--- a/gcc/ada/exp_unst.adb
+++ b/gcc/ada/exp_unst.adb
@@ -746,6 +746,10 @@ package body Exp_Unst is
             procedure Register_Subprogram (E : Entity_Id; Bod : Node_Id) is
                L : constant Nat := Get_Level (Subp, E);
 
+            --  Subprograms declared in tasks and protected types cannot
+            --  be eliminated because calls to them may be in other units,
+            --  so they must be treated as reachable.
+
             begin
                --  Subprograms declared in tasks and protected types cannot
                --  be eliminated because calls to them may be in other units,
@@ -756,10 +760,6 @@ package body Exp_Unst is
                    Bod           => Bod,
                    Lev           => L,
                    Reachable     => In_Synchronized_Unit (E),
-
-                   --  Subprograms declared in tasks and protected types are
-                   --  reachable and cannot be eliminated.
-
                    Uplevel_Ref   => L,
                    Declares_AREC => False,
                    Uents         => No_Elist,
@@ -1148,7 +1148,7 @@ package body Exp_Unst is
                      return Skip;
                   end if;
 
-               --  Pragmas and component declarations can be ignored
+               --  Pragmas and component declarations can be ignored.
                --  Quantified expressions are expanded into explicit loops
                --  and the original epression must be ignored.
 
@@ -1383,10 +1383,10 @@ package body Exp_Unst is
 
                         --  If this entity was marked reachable because it is
                         --  in a task or protected type, there may not appear
-                        --  to be any calls to it, which would normally adjust
-                        --  the levels of the parent subprograms. So we need to
-                        --  be sure that the uplevel reference of that entity
-                        --  takes into account possible calls.
+                        --  to be any calls to it, which would normally
+                        --  adjust the levels of the parent subprograms.
+                        --  So we need to be sure that the uplevel reference
+                        --  of that entity takes into account possible calls.
 
                         if In_Synchronized_Unit (SUBF.Ent)
                           and then SUBT.Lev < SUBI.Uplevel_Ref
@@ -1627,7 +1627,7 @@ package body Exp_Unst is
       --  Loop through subprograms
 
       Subp_Loop : declare
-         Addr : constant Entity_Id := RTE (RE_Address);
+         Addr : Entity_Id := Empty;
 
       begin
          for J in Subps_First .. Subps.Last loop
@@ -1745,9 +1745,14 @@ package body Exp_Unst is
 
                   begin
                      --  Build list of component declarations for ARECnT
+                     --  and load System.Address.
 
                      Clist := Empty_List;
 
+                     if No (Addr) then
+                        Addr := RTE (RE_Address);
+                     end if;
+
                      --  If we are in a subprogram that has a static link that
                      --  is passed in (as indicated by ARECnF being defined),
                      --  then include ARECnU : ARECmPT where ARECmPT comes from