[gcc r13-1479] [Ada] Remove unnecessary dead code after calls to nonreturning procedures

[gcc r13-1479] [Ada] Remove unnecessary dead code after calls to nonreturning procedures

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:9fde6c7114f079b38ebee420a541e14387bcc928

commit r13-1479-g9fde6c7114f079b38ebee420a541e14387bcc928
Author: Piotr Trojanek <trojanek@adacore.com>
Date:   Thu Jun 2 17:32:15 2022 +0200

    [Ada] Remove unnecessary dead code after calls to nonreturning procedures
    
    A new warning about unreachable code that follows calls to procedures
    with No_Return would flag some dead defensive code. Comments next to
    this code suggest that it was added to please some ancient version of
    the compiler, but recent releases of GNAT do not require such a code.
    
    gcc/ada/
    
            * gnatls.adb (Corresponding_Sdep_Entry): Remove dead return
            statement in defensive path; there is another return statement
            for a normal execution of this routine, so rule Ada RM 6.5(5),
            which requires function to have at least one return statement is
            still satisfied.
            (Gnatls): Remove dead, call to nonreturning Exit_Program after
            Output_License_Information which itself does not return.
            * libgnat/a-exstat.adb (Bad_EO): Remove raise statement that was
            meant to please some ancient version of GNAT.
            * libgnat/g-awk.adb (Raise_With_Info): Likewise.
            * sem_attr.adb (Check_Reference): Remove dead return statement;
            rule Ada RM 6.5(5), which requires function to have at least one
            return statement is still satisfied.
            (Analyze_Attribute): Remove dead exit statement.
            (Check_Reference): Same as above.
            * sem_ch12.adb (Instantiate_Formal_Package): Remove dead raise
            statement; it was inconsistent with other calls to
            Abandon_Instantiation, which are not followed by a raise
            statement.
            * sem_prag.adb (Process_Convention): Remove dead defensive
            assignment.
            (Interrupt_State): Remove dead defensive exit statement.
            (Do_SPARK_Mode): Likewise.
            * sfn_scan.adb (Scan_String): Remove dead defensive assignment.

Diff:
---
 gcc/ada/gnatls.adb           | 2 --
 gcc/ada/libgnat/a-exstat.adb | 7 -------
 gcc/ada/libgnat/g-awk.adb    | 1 -
 gcc/ada/sem_attr.adb         | 3 ---
 gcc/ada/sem_ch12.adb         | 1 -
 gcc/ada/sem_prag.adb         | 3 ---
 gcc/ada/sfn_scan.adb         | 1 -
 7 files changed, 18 deletions(-)

diff --git a/gcc/ada/gnatls.adb b/gcc/ada/gnatls.adb
index 9b62f71d68e..72445268f00 100644
--- a/gcc/ada/gnatls.adb
+++ b/gcc/ada/gnatls.adb
@@ -319,7 +319,6 @@ procedure Gnatls is
       Write_Eol;
       Error_Msg ("wrong ALI format, can't find dependency line for $ in {");
       Exit_Program (E_Fatal);
-      return No_Sdep_Id;
    end Corresponding_Sdep_Entry;
 
    -------------------------
@@ -2051,7 +2050,6 @@ begin
    if License then
       if Arg_Count = 2 then
          Output_License_Information;
-         Exit_Program (E_Success);
 
       else
          Set_Standard_Error;
diff --git a/gcc/ada/libgnat/a-exstat.adb b/gcc/ada/libgnat/a-exstat.adb
index a3f808eada8..acc251649cd 100644
--- a/gcc/ada/libgnat/a-exstat.adb
+++ b/gcc/ada/libgnat/a-exstat.adb
@@ -109,13 +109,6 @@ package body Stream_Attributes is
          Raise_Exception
            (Program_Error'Identity,
             "bad exception occurrence in stream input");
-
-         --  The following junk raise of Program_Error is required because
-         --  this is a No_Return procedure, and unfortunately Raise_Exception
-         --  can return (this particular call can't, but the back end is not
-         --  clever enough to know that).
-
-         raise Program_Error;
       end Bad_EO;
 
       procedure Next_String is
diff --git a/gcc/ada/libgnat/g-awk.adb b/gcc/ada/libgnat/g-awk.adb
index 1c887853fa9..9b2e127b3bb 100644
--- a/gcc/ada/libgnat/g-awk.adb
+++ b/gcc/ada/libgnat/g-awk.adb
@@ -1211,7 +1211,6 @@ package body GNAT.AWK is
       Exceptions.Raise_Exception
         (E,
          '[' & Filename & ':' & Line & "] " & Message);
-      raise Constraint_Error; -- to please GNAT as this is a No_Return proc
    end Raise_With_Info;
 
    ---------------
diff --git a/gcc/ada/sem_attr.adb b/gcc/ada/sem_attr.adb
index be600872a1d..6a35358261e 100644
--- a/gcc/ada/sem_attr.adb
+++ b/gcc/ada/sem_attr.adb
@@ -4747,7 +4747,6 @@ package body Sem_Attr is
                   Error_Attr
                     ("prefix of attribute % cannot reference local entities",
                      Nod);
-                  return Abandon;
                else
                   return OK;
                end if;
@@ -4989,7 +4988,6 @@ package body Sem_Attr is
             else
                Error_Attr
                  ("attribute % cannot appear in body or accept statement", N);
-               exit;
             end if;
          end loop;
 
@@ -5383,7 +5381,6 @@ package body Sem_Attr is
                   Error_Attr
                     ("prefix of attribute % cannot reference local entities",
                      Nod);
-                  return Abandon;
 
                --  Otherwise keep inspecting the prefix
 
diff --git a/gcc/ada/sem_ch12.adb b/gcc/ada/sem_ch12.adb
index c5f2eed96fd..dcc0dac4342 100644
--- a/gcc/ada/sem_ch12.adb
+++ b/gcc/ada/sem_ch12.adb
@@ -10572,7 +10572,6 @@ package body Sem_Ch12 is
          Error_Msg_N
            ("expect package instance to instantiate formal", Actual);
          Abandon_Instantiation (Actual);
-         raise Program_Error;
 
       else
          Actual_Pack := Entity (Actual);
diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
index 89c45da10bb..3660c75fc69 100644
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -8336,7 +8336,6 @@ package body Sem_Prag is
                Error_Pragma_Arg
                  ("argument of pragma% must be subprogram or access type",
                   Arg2);
-               Subp := Empty;
             end if;
 
             --  ISO C requires a named parameter before the ellipsis, so a
@@ -18641,7 +18640,6 @@ package body Sem_Prag is
                     Interrupt_States.Table (IST_Num).Pragma_Loc;
                   Error_Pragma_Arg
                     ("state conflicts with that given #", Arg2);
-                  exit;
                end if;
 
                IST_Num := IST_Num + 1;
@@ -23762,7 +23760,6 @@ package body Sem_Prag is
 
                   else
                      Pragma_Misplaced;
-                     exit;
                   end if;
 
                   Prev (Stmt);
diff --git a/gcc/ada/sfn_scan.adb b/gcc/ada/sfn_scan.adb
index b6ab92fe46b..b428ed7f0cf 100644
--- a/gcc/ada/sfn_scan.adb
+++ b/gcc/ada/sfn_scan.adb
@@ -622,7 +622,6 @@ package body SFN_Scan is
          Q := '%';
       else
          Error ("bad string");
-         Q := '"';
       end if;
 
       --  Scan out the string, B points to first char