[Ada] Make loop labels unique for front-end inlined calls

[Ada] Make loop labels unique for front-end inlined calls

This patch transforms loop labels in the body of subprograms that are to
be inlined by the front-end, to prevent accidental duplication of loop
labels, which might make the resulting source illegal.

----
Source program:
----
package P is
   procedure Get_Rom_Addr_Offset
     with Inline_Always;
end P;
----
package body P is
   procedure Get_Rom_Addr_Offset is
      X : Integer;
   begin
      Main_Block :
      for I in 1 .. 10 loop
         X := 2;
         exit Main_Block when I > 4;
      other_loop:
         for J in character'('a') .. 'z' loop
            if I < 5 then
               exit Main_Block when J = 'k';
            else
               Exit Other_Loop;
            end if;
         end loop other_loop;
      end loop Main_Block;
   end Get_Rom_Addr_Offset;

   procedure P2 is
   begin
      Main_Block :
      for I in 1 .. 1 loop
         Get_Rom_Addr_Offset;
      end loop Main_Block;
   end P2;
end P;
----
Command:

   gcc -c -gnatN -gnatd.u -gnatDG p.adb

----
Output
----

package body p is

   procedure p__get_rom_addr_offset is
      x : integer;
      other_loop : label
      main_block : label
   begin
      main_block : for i in 1 .. 10 loop
         x := 2;
         exit main_block when i > 4;
         other_loop : for j in 'a' .. 'z' loop
            if i < 5 then
               exit main_block when j = 'k';
            else
               exit other_loop;
            end if;
         end loop other_loop;
      end loop main_block;
      return;
   end p__get_rom_addr_offset;

   procedure p__p2 is
      main_block : label
   begin
      main_block : for i in 1 .. 1 loop
         B6b : declare
            x : integer;
            other_loopL10b : label
            main_blockL9b : label
         begin
            main_blockL9b : for i in 1 .. 10 loop
               x := 2;
               exit main_blockL9b when i > 4;
               other_loopL10b : for j in 'a' .. 'z' loop
                  if i < 5 then
                     exit main_blockL9b when j = 'k';
                  else
                     exit other_loopL10b;
                  end if;
               end loop other_loopL10b;
            end loop main_blockL9b;
         end B6b;
      end loop main_block;
      return;
   end p__p2;
begin
   null;
end p;

2019-07-03  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* inline.adb (Make_Loop_Labels_Unique):  New procedure to modify
	the source code of subprograms that are inlined by the
	front-end, to prevent accidental duplication between loop labels
	in the inlined code and the code surrounding the inlined call.

From-SVN: r272967