2012-11-06 Robert Dewar <dewar@adacore.com>

	* checks.ads, checks.adb, exp_ch4.adb: Minor changes throughout for
	new overflow checking.
	* exp_util.adb (Insert_Actions): Remove special casing of
	Overflow_Check.
	* gnat1drv.adb (Adjust_Global_Switches): Fixes for new handling
	of overflow checks.
	* sem.adb (Analyze): Remove special casing of Overflow_Check
	(Analyze_List): ditto.
	* sem_prag.adb (Analyze_Pragma, case Overflow_Checks): Remove
	SUPPRESSED and change CHECKED to STRICT.
	* sem_res.adb (Analyze_And_Resolve): No longer treat
	Overflow_Check specially.
	(Preanalyze_And_Resolve): ditto.
	(Resolve): ditto.
	* snames.ads-tmpl: Replace Name_Checked by Name_Strict.
	* switch-c.adb (Get_Overflow_Mode): Eliminate 0 setting,
	CHECKED => STRICT.
	* types.ads (Overflow_Check_Type): Remove Suppressed, change
	Checked to Strict (Suppress_Record): Overflow check controlled
	by Suppress array.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@193233 138bc75d-0d04-0410-961f-82ee72b054a4

12 files changed, 370 insertions, 409 deletions

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index cfa05a20601..d2c739f4fa1 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,26 @@
+2012-11-06  Robert Dewar  <dewar@adacore.com>
+
+	* checks.ads, checks.adb, exp_ch4.adb: Minor changes throughout for
+	new overflow checking.
+	* exp_util.adb (Insert_Actions): Remove special casing of
+	Overflow_Check.
+	* gnat1drv.adb (Adjust_Global_Switches): Fixes for new handling
+	of overflow checks.
+	* sem.adb (Analyze): Remove special casing of Overflow_Check
+	(Analyze_List): ditto.
+	* sem_prag.adb (Analyze_Pragma, case Overflow_Checks): Remove
+	SUPPRESSED and change CHECKED to STRICT.
+	* sem_res.adb (Analyze_And_Resolve): No longer treat
+	Overflow_Check specially.
+	(Preanalyze_And_Resolve): ditto.
+	(Resolve): ditto.
+	* snames.ads-tmpl: Replace Name_Checked by Name_Strict.
+	* switch-c.adb (Get_Overflow_Mode): Eliminate 0 setting,
+	CHECKED => STRICT.
+	* types.ads (Overflow_Check_Type): Remove Suppressed, change
+	Checked to Strict (Suppress_Record): Overflow check controlled
+	by Suppress array.
+
 2012-11-06  Ed Schonberg  <schonberg@adacore.com>
 
 	* sem_res.adb (Preanalyze_And_Resolve): In Alfa mode do not
diff --git a/gcc/ada/checks.adb b/gcc/ada/checks.adb
index 406d292f09e..b0262dba815 100644
--- a/gcc/ada/checks.adb
+++ b/gcc/ada/checks.adb
@@ -194,18 +194,19 @@ package body Checks is
    -- Local Subprograms --
    -----------------------
 
-   procedure Apply_Arithmetic_Overflow_Checked_Suppressed (N : Node_Id);
+   procedure Apply_Arithmetic_Overflow_Strict (N : Node_Id);
    --  Used to apply arithmetic overflow checks for all cases except operators
    --  on signed arithmetic types in MINIMIZED/ELIMINATED case (for which we
-   --  call Apply_Arithmetic_Overflow_Minimized_Eliminated below). N is always
-   --  a signed integer arithmetic operator (if and case expressions are not
-   --  included for this case).
+   --  call Apply_Arithmetic_Overflow_Minimized_Eliminated below). N can be a
+   --  signed integer arithmetic operator (but not an if or case expression).
+   --  It is also called for types other than signed integers.
 
    procedure Apply_Arithmetic_Overflow_Minimized_Eliminated (Op : Node_Id);
    --  Used to apply arithmetic overflow checks for the case where the overflow
-   --  checking mode is MINIMIZED or ELIMINATED (and the Do_Overflow_Check flag
-   --  is known to be set) and we have a signed integer arithmetic op (which
-   --  includes the case of if and case expressions).
+   --  checking mode is MINIMIZED or ELIMINATED and we have a signed integer
+   --  arithmetic op (which includes the case of if and case expressions). Note
+   --  that Do_Overflow_Check may or may not be set for node Op. In these modes
+   --  we have work to do even if overflow checking is suppressed.
 
    procedure Apply_Division_Check
      (N   : Node_Id;
@@ -766,14 +767,12 @@ package body Checks is
    begin
       --  Use old routine in almost all cases (the only case we are treating
       --  specially is the case of a signed integer arithmetic op with the
-      --  Do_Overflow_Check flag set on the node, and the overflow checking
-      --  mode is MINIMIZED or ELIMINATED).
+      --  overflow checking mode set to MINIMIZED or ELIMINATED).
 
-      if Overflow_Check_Mode (Etype (N)) not in Minimized_Or_Eliminated
-        or else not Do_Overflow_Check (N)
+      if Overflow_Check_Mode = Strict
         or else not Is_Signed_Integer_Arithmetic_Op (N)
       then
-         Apply_Arithmetic_Overflow_Checked_Suppressed (N);
+         Apply_Arithmetic_Overflow_Strict (N);
 
       --  Otherwise use the new routine for the case of a signed integer
       --  arithmetic op, with Do_Overflow_Check set to True, and the checking
@@ -784,9 +783,9 @@ package body Checks is
       end if;
    end Apply_Arithmetic_Overflow_Check;
 
-   --------------------------------------------------
-   -- Apply_Arithmetic_Overflow_Checked_Suppressed --
-   --------------------------------------------------
+   --------------------------------------
+   -- Apply_Arithmetic_Overflow_Strict --
+   --------------------------------------
 
    --  This routine is called only if the type is an integer type, and a
    --  software arithmetic overflow check may be needed for op (add, subtract,
@@ -795,21 +794,28 @@ package body Checks is
    --  operation into a more complex sequence of tests that ensures that
    --  overflow is properly caught.
 
-   --  This is used in SUPPRESSED/CHECKED modes. It is identical to the
-   --  code for these cases before the big overflow earthquake, thus ensuring
-   --  that in these modes we have compatible behavior (and reliability) to
-   --  what was there before. It is also called for types other than signed
-   --  integers, and if the Do_Overflow_Check flag is off.
+   --  This is used in CHECKED modes. It is identical to the code for this
+   --  cases before the big overflow earthquake, thus ensuring that in this
+   --  modes we have compatible behavior (and reliability) to what was there
+   --  before. It is also called for types other than signed integers, and if
+   --  the Do_Overflow_Check flag is off.
 
    --  Note: we also call this routine if we decide in the MINIMIZED case
    --  to give up and just generate an overflow check without any fuss.
 
-   procedure Apply_Arithmetic_Overflow_Checked_Suppressed (N : Node_Id) is
+   procedure Apply_Arithmetic_Overflow_Strict (N : Node_Id) is
       Loc  : constant Source_Ptr := Sloc (N);
       Typ  : constant Entity_Id  := Etype (N);
       Rtyp : constant Entity_Id  := Root_Type (Typ);
 
    begin
+      --  Nothing to do if Do_Overflow_Check not set or overflow checks
+      --  suppressed.
+
+      if not Do_Overflow_Check (N) then
+         return;
+      end if;
+
       --  An interesting special case. If the arithmetic operation appears as
       --  the operand of a type conversion:
 
@@ -1067,7 +1073,7 @@ package body Checks is
          when RE_Not_Available =>
             return;
       end;
-   end Apply_Arithmetic_Overflow_Checked_Suppressed;
+   end Apply_Arithmetic_Overflow_Strict;
 
    ----------------------------------------------------
    -- Apply_Arithmetic_Overflow_Minimized_Eliminated --
@@ -1075,7 +1081,6 @@ package body Checks is
 
    procedure Apply_Arithmetic_Overflow_Minimized_Eliminated (Op : Node_Id) is
       pragma Assert (Is_Signed_Integer_Arithmetic_Op (Op));
-      pragma Assert (Do_Overflow_Check (Op));
 
       Loc : constant Source_Ptr := Sloc (Op);
       P   : constant Node_Id    := Parent (Op);
@@ -1086,8 +1091,7 @@ package body Checks is
       Result_Type : constant Entity_Id := Etype (Op);
       --  Original result type
 
-      Check_Mode : constant Overflow_Check_Type :=
-                     Overflow_Check_Mode (Etype (Op));
+      Check_Mode : constant Overflow_Check_Type := Overflow_Check_Mode;
       pragma Assert (Check_Mode in Minimized_Or_Eliminated);
 
       Lo, Hi : Uint;
@@ -1102,7 +1106,7 @@ package body Checks is
 
       --  In all these cases, we will process at the higher level (and then
       --  this node will be processed during the downwards recursion that
-      --  is part of the processing in Minimize_Eliminate_Overflow_Checks).
+      --  is part of the processing in Minimize_Eliminate_Overflows).
 
       if Is_Signed_Integer_Arithmetic_Op (P)
         or else Nkind (P) in N_Membership_Test
@@ -1127,7 +1131,7 @@ package body Checks is
       --  will still be in Bignum mode if either of its operands are of type
       --  Bignum).
 
-      Minimize_Eliminate_Overflow_Checks (Op, Lo, Hi, Top_Level => True);
+      Minimize_Eliminate_Overflows (Op, Lo, Hi, Top_Level => True);
 
       --  That call may but does not necessarily change the result type of Op.
       --  It is the job of this routine to undo such changes, so that at the
@@ -1213,7 +1217,7 @@ package body Checks is
 
       --  Here we know the result is Long_Long_Integer'Base, of that it has
       --  been rewritten because the parent operation is a conversion. See
-      --  Apply_Arithmetic_Overflow_Checked_Suppressed.Conversion_Optimization.
+      --  Apply_Arithmetic_Overflow_Strict.Conversion_Optimization.
 
       else
          pragma Assert
@@ -1678,7 +1682,7 @@ package body Checks is
       Left  : constant Node_Id    := Left_Opnd (N);
       Right : constant Node_Id    := Right_Opnd (N);
 
-      Mode : constant Overflow_Check_Type := Overflow_Check_Mode (Typ);
+      Mode : constant Overflow_Check_Type := Overflow_Check_Mode;
       --  Current overflow checking mode
 
       LLB : Uint;
@@ -1693,15 +1697,13 @@ package body Checks is
       --  Don't actually use this value
 
    begin
-      --  If we are operating in MINIMIZED or ELIMINATED mode, and the
-      --  Do_Overflow_Check flag is set and we are operating on signed
-      --  integer types, then the only thing this routine does is to call
-      --  Apply_Arithmetic_Overflow_Minimized_Eliminated. That procedure will
-      --  (possibly later on during recursive downward calls), make sure that
-      --  any needed overflow and division checks are properly applied.
+      --  If we are operating in MINIMIZED or ELIMINATED mode, and we are
+      --  operating on signed integer types, then the only thing this routine
+      --  does is to call Apply_Arithmetic_Overflow_Minimized_Eliminated. That
+      --  procedure will (possibly later on during recursive downward calls),
+      --  ensure that any needed overflow/division checks are properly applied.
 
       if Mode in Minimized_Or_Eliminated
-        and then Do_Overflow_Check (N)
         and then Is_Signed_Integer_Type (Typ)
       then
          Apply_Arithmetic_Overflow_Minimized_Eliminated (N);
@@ -1726,7 +1728,9 @@ package body Checks is
 
          --  Deal with overflow check
 
-         if Do_Overflow_Check (N) and then Mode /= Suppressed then
+         if Do_Overflow_Check (N)
+           and then not Overflow_Checks_Suppressed (Etype (N))
+         then
 
             --  Test for extremely annoying case of xxx'First divided by -1
             --  for division of signed integer types (only overflow case).
@@ -3093,6 +3097,7 @@ package body Checks is
 
          begin
             if not Overflow_Checks_Suppressed (Target_Base)
+              and then not Overflow_Checks_Suppressed (Target_Type)
               and then not
                 In_Subrange_Of (Expr_Type, Target_Base, Fixed_Int => Conv_OK)
               and then not Float_To_Int
@@ -4420,7 +4425,7 @@ package body Checks is
 
    procedure Enable_Overflow_Check (N : Node_Id) is
       Typ  : constant Entity_Id           := Base_Type (Etype (N));
-      Mode : constant Overflow_Check_Type := Overflow_Check_Mode (Etype (N));
+      Mode : constant Overflow_Check_Type := Overflow_Check_Mode;
       Chk  : Nat;
       OK   : Boolean;
       Ent  : Entity_Id;
@@ -4438,7 +4443,7 @@ package body Checks is
 
       --  No check if overflow checks suppressed for type of node
 
-      if Mode = Suppressed then
+      if Overflow_Checks_Suppressed (Etype (N)) then
          return;
 
       --  Nothing to do for unsigned integer types, which do not overflow
@@ -4447,23 +4452,28 @@ package body Checks is
          return;
       end if;
 
-      --  This is the point at which processing for CHECKED mode diverges
+      --  This is the point at which processing for STRICT mode diverges
       --  from processing for MINIMIZED/ELIMINATED modes. This divergence is
       --  probably more extreme that it needs to be, but what is going on here
       --  is that when we introduced MINIMIZED/ELIMINATED modes, we wanted
-      --  to leave the processing for CHECKED mode untouched. There were
+      --  to leave the processing for STRICT mode untouched. There were
       --  two reasons for this. First it avoided any incompatible change of
-      --  behavior. Second, it guaranteed that CHECKED mode continued to be
+      --  behavior. Second, it guaranteed that STRICT mode continued to be
       --  legacy reliable.
 
-      --  The big difference is that in CHECKED mode there is a fair amount of
+      --  The big difference is that in STRICT mode there is a fair amount of
       --  circuitry to try to avoid setting the Do_Overflow_Check flag if we
       --  know that no check is needed. We skip all that in the two new modes,
       --  since really overflow checking happens over a whole subtree, and we
       --  do the corresponding optimizations later on when applying the checks.
 
       if Mode in Minimized_Or_Eliminated then
-         Activate_Overflow_Check (N);
+         if not (Overflow_Checks_Suppressed (Etype (N)))
+           and then not (Is_Entity_Name (N)
+                          and then Overflow_Checks_Suppressed (Entity (N)))
+         then
+            Activate_Overflow_Check (N);
+         end if;
 
          if Debug_Flag_CC then
             w ("Minimized/Eliminated mode");
@@ -4472,7 +4482,7 @@ package body Checks is
          return;
       end if;
 
-      --  Remainder of processing is for Checked case, and is unchanged from
+      --  Remainder of processing is for STRICT case, and is unchanged from
       --  earlier versions preceding the addition of MINIMIZED/ELIMINATED.
 
       --  Nothing to do if the range of the result is known OK. We skip this
@@ -6685,9 +6695,9 @@ package body Checks is
                     New_Reference_To (M, Loc))))));
    end Make_Bignum_Block;
 
-   ----------------------------------------
-   -- Minimize_Eliminate_Overflow_Checks --
-   ----------------------------------------
+   ----------------------------------
+   -- Minimize_Eliminate_Overflows --
+   ----------------------------------
 
    --  This is a recursive routine that is called at the top of an expression
    --  tree to properly process overflow checking for a whole subtree by making
@@ -6697,14 +6707,13 @@ package body Checks is
    --  it would interfere with semantic analysis).
 
    --  What happens is that if MINIMIZED/ELIMINATED mode is in effect then
-   --  the operator expansion routines, as well as the expansion routines
-   --  for if/case expression test the Do_Overflow_Check flag and if it is
-   --  set they (for the moment) do nothing except call the routine to apply
-   --  the overflow check (Apply_Arithmetic_Overflow_Check). That routine
-   --  does nothing for non top-level nodes, so at the point where the call
-   --  is made for the top level node, the entire expression subtree has not
-   --  been expanded, or processed for overflow. All that has to happen as a
-   --  result of the top level call to this routine.
+   --  the operator expansion routines, as well as the expansion routines for
+   --  if/case expression, do nothing (for the moment) except call the routine
+   --  to apply the overflow check (Apply_Arithmetic_Overflow_Check). That
+   --  routine does nothing for non top-level nodes, so at the point where the
+   --  call is made for the top level node, the entire expression subtree has
+   --  not been expanded, or processed for overflow. All that has to happen as
+   --  a result of the top level call to this routine.
 
    --  As noted above, the overflow processing works by making recursive calls
    --  for the operands, and figuring out what to do, based on the processing
@@ -6716,11 +6725,10 @@ package body Checks is
    --  the node (if it has been modified by the overflow check processing). The
    --  Analyzed_Flag is set to False before the reexpand/reanalyze. To avoid
    --  a recursive call into the whole overflow apparatus, an important rule
-   --  for this call is that either Do_Overflow_Check must be False, or if
-   --  it is set, then the overflow checking mode must be temporarily set
-   --  to CHECKED/SUPPRESSED. Either step will avoid the unwanted recursion.
+   --  for this call is that the overflow handling mode must be temporarily set
+   --  to STRICT.
 
-   procedure Minimize_Eliminate_Overflow_Checks
+   procedure Minimize_Eliminate_Overflows
      (N         : Node_Id;
       Lo        : out Uint;
       Hi        : out Uint;
@@ -6730,7 +6738,7 @@ package body Checks is
       pragma Assert (Is_Signed_Integer_Type (Rtyp));
       --  Result type, must be a signed integer type
 
-      Check_Mode : constant Overflow_Check_Type := Overflow_Check_Mode (Empty);
+      Check_Mode : constant Overflow_Check_Type := Overflow_Check_Mode;
       pragma Assert (Check_Mode in Minimized_Or_Eliminated);
 
       Loc : constant Source_Ptr := Sloc (N);
@@ -6764,18 +6772,24 @@ package body Checks is
       --  Set True if one or more operands is already of type Long_Long_Integer
       --  which means that if the result is known to be in the result type
       --  range, then we must convert such operands back to the result type.
-      --  This switch is properly set only when Bignum_Operands is False.
-
-      procedure Reexpand (C : Suppressed_Or_Checked);
-      --  This is called when we have not modified the node, so we do not need
-      --  to reanalyze it. But we do want to reexpand it in either SUPPRESSED
-      --  or CHECKED mode (as indicated by the argument C) to get proper
-      --  expansion. It is important that we reset the mode to SUPPRESSED or
-      --  CHECKED, since if we leave it in MINIMIZED or ELIMINATED mode we
-      --  would reenter this routine recursively which would not be good!
-      --  Note that this is not just an optimization, testing has showed up
-      --  several complex cases in which reanalyzing an already analyzed node
-      --  causes incorrect behavior.
+
+      procedure Reanalyze (Typ : Entity_Id; Suppress : Boolean := False);
+      --  This is called when we have modified the node and we therefore need
+      --  to reanalyze it. It is important that we reset the mode to STRICT for
+      --  this reanalysis, since if we leave it in MINIMIZED or ELIMINATED mode
+      --  we would reenter this routine recursively which would not be good!
+      --  The argument Suppress is set True if we also want to suppress
+      --  overflow checking for the reexpansion (this is set when we know
+      --  overflow is not possible). Typ is the type for the reanalysis.
+
+      procedure Reexpand (Suppress : Boolean := False);
+      --  This is like Reanalyze, but does not do the Analyze step, it only
+      --  does a reexpansion. We do this reexpansion in STRICT mode, so that
+      --  instead of reentering the MINIMIZED/ELIMINATED mode processing, we
+      --  follow the normal expansion path (e.g. converting A**4 to A**2**2).
+      --  Note that skipping reanalysis is not just an optimization, testing
+      --  has showed up several complex cases in which reanalyzing an already
+      --  analyzed node causes incorrect behavior.
 
       function In_Result_Range return Boolean;
       --  Returns True iff Lo .. Hi are within range of the result type
@@ -6829,25 +6843,62 @@ package body Checks is
          end if;
       end Min;
 
+      ---------------
+      -- Reanalyze --
+      ---------------
+
+      procedure Reanalyze (Typ : Entity_Id; Suppress : Boolean := False) is
+         Svg : constant Overflow_Check_Type :=
+                 Scope_Suppress.Overflow_Checks_General;
+         Sva : constant Overflow_Check_Type :=
+                 Scope_Suppress.Overflow_Checks_Assertions;
+         Svo : constant Boolean             :=
+                 Scope_Suppress.Suppress (Overflow_Check);
+
+      begin
+         Scope_Suppress.Overflow_Checks_General    := Strict;
+         Scope_Suppress.Overflow_Checks_Assertions := Strict;
+
+         if Suppress then
+            Scope_Suppress.Suppress (Overflow_Check) := True;
+         end if;
+
+         Analyze_And_Resolve (N, Typ);
+
+         Scope_Suppress.Suppress (Overflow_Check)  := Svo;
+         Scope_Suppress.Overflow_Checks_General    := Svg;
+         Scope_Suppress.Overflow_Checks_Assertions := Sva;
+      end Reanalyze;
+
       --------------
       -- Reexpand --
       --------------
 
-      procedure Reexpand (C : Suppressed_Or_Checked) is
+      procedure Reexpand (Suppress : Boolean := False) is
          Svg : constant Overflow_Check_Type :=
                  Scope_Suppress.Overflow_Checks_General;
          Sva : constant Overflow_Check_Type :=
                  Scope_Suppress.Overflow_Checks_Assertions;
+         Svo : constant Boolean             :=
+                 Scope_Suppress.Suppress (Overflow_Check);
+
       begin
-         Scope_Suppress.Overflow_Checks_General    := C;
-         Scope_Suppress.Overflow_Checks_Assertions := C;
+         Scope_Suppress.Overflow_Checks_General    := Strict;
+         Scope_Suppress.Overflow_Checks_Assertions := Strict;
          Set_Analyzed (N, False);
+
+         if Suppress then
+            Scope_Suppress.Suppress (Overflow_Check) := True;
+         end if;
+
          Expand (N);
+
+         Scope_Suppress.Suppress (Overflow_Check)  := Svo;
          Scope_Suppress.Overflow_Checks_General    := Svg;
          Scope_Suppress.Overflow_Checks_Assertions := Sva;
       end Reexpand;
 
-   --  Start of processing for Minimize_Eliminate_Overflow_Checks
+   --  Start of processing for Minimize_Eliminate_Overflows
 
    begin
       --  Case where we do not have a signed integer arithmetic operation
@@ -6884,14 +6935,14 @@ package body Checks is
          begin
             Bignum_Operands := False;
 
-            Minimize_Eliminate_Overflow_Checks
+            Minimize_Eliminate_Overflows
               (Then_DE, Lo, Hi, Top_Level => False);
 
             if Lo = No_Uint then
                Bignum_Operands := True;
             end if;
 
-            Minimize_Eliminate_Overflow_Checks
+            Minimize_Eliminate_Overflows
               (Else_DE, Rlo, Rhi, Top_Level => False);
 
             if Rlo = No_Uint then
@@ -6918,8 +6969,7 @@ package body Checks is
                      Convert_To_Bignum (Else_DE)),
                    Is_Elsif    => Is_Elsif (N)));
 
-               Analyze_And_Resolve
-                 (N, RTE (RE_Bignum), Suppress => Overflow_Check);
+               Reanalyze (RTE (RE_Bignum), Suppress => True);
 
             --  If we have no Long_Long_Integer operands, then we are in result
             --  range, since it means that none of our operands felt the need
@@ -6930,7 +6980,7 @@ package body Checks is
 
             elsif not Long_Long_Integer_Operands then
                Set_Do_Overflow_Check (N, False);
-               Reexpand (Suppressed);
+               Reexpand;
 
             --  Otherwise convert us to long long integer mode. Note that we
             --  don't need any further overflow checking at this level.
@@ -6943,8 +6993,7 @@ package body Checks is
                --  Now reanalyze with overflow checks off
 
                Set_Do_Overflow_Check (N, False);
-               Set_Analyzed (N, False);
-               Analyze_And_Resolve (N, LLIB, Suppress => Overflow_Check);
+               Reanalyze (LLIB, Suppress => True);
             end if;
          end;
 
@@ -6968,7 +7017,7 @@ package body Checks is
                   Aexp : constant Node_Id := Expression (Alt);
 
                begin
-                  Minimize_Eliminate_Overflow_Checks
+                  Minimize_Eliminate_Overflows
                     (Aexp, Lo, Hi, Top_Level => False);
 
                   if Lo = No_Uint then
@@ -6991,7 +7040,7 @@ package body Checks is
 
             if not (Bignum_Operands or Long_Long_Integer_Operands) then
                Set_Do_Overflow_Check (N, False);
-               Reexpand (Suppressed);
+               Reexpand (Suppress => True);
 
             --  Otherwise we are going to rebuild the case expression using
             --  either bignum or long long integer operands throughout.
@@ -7028,7 +7077,7 @@ package body Checks is
                       Expression   => Expression (N),
                       Alternatives => New_Alts));
 
-                  Analyze_And_Resolve (N, Rtype, Suppress => Overflow_Check);
+                  Reanalyze (Rtype, Suppress => True);
                end;
             end if;
          end;
@@ -7040,11 +7089,11 @@ package body Checks is
       --  operands to get the ranges (and to properly process the subtree
       --  that lies below us!)
 
-      Minimize_Eliminate_Overflow_Checks
+      Minimize_Eliminate_Overflows
         (Right_Opnd (N), Rlo, Rhi, Top_Level => False);
 
       if Binary then
-         Minimize_Eliminate_Overflow_Checks
+         Minimize_Eliminate_Overflows
            (Left_Opnd (N), Llo, Lhi, Top_Level => False);
       end if;
 
@@ -7356,7 +7405,7 @@ package body Checks is
         and then In_Result_Range
       then
          Set_Do_Overflow_Check (N, False);
-         Reexpand (Suppressed);
+         Reexpand (Suppress => True);
          return;
 
       --  Here we know that we are not in the result range, and in the general
@@ -7380,22 +7429,17 @@ package body Checks is
 
         and then Nkind (Parent (N)) /= N_Type_Conversion
       then
-         --  Here we will keep the original types, but we do need an overflow
-         --  check, so we will set Do_Overflow_Check to True (actually it is
-         --  true already, or how would we have got here?).
-
-         pragma Assert (Do_Overflow_Check (N));
-         Set_Analyzed (N, False);
+         --  Here keep original types, but we need to complete analysis
 
          --  One subtlety. We can't just go ahead and do an analyze operation
          --  here because it will cause recursion into the whole MINIMIZED/
          --  ELIMINATED overflow processing which is not what we want. Here
          --  we are at the top level, and we need a check against the result
-         --  mode (i.e. we want to use Checked mode). So do exactly that!
+         --  mode (i.e. we want to use STRICT mode). So do exactly that!
          --  Also, we have not modified the node, so this is a case where
          --  we need to reexpand, but not reanalyze.
 
-         Reexpand (Checked);
+         Reexpand;
          return;
 
       --  Cases where we do the operation in Bignum mode. This happens either
@@ -7421,17 +7465,18 @@ package body Checks is
          --  set True). In this case, there is no point in moving into Bignum
          --  mode to prevent overflow if the caller will immediately convert
          --  the Bignum value back to LLI with an overflow check. It's more
-         --  efficient to stay in LLI mode with an overflow check.
+         --  efficient to stay in LLI mode with an overflow check (if needed)
 
          if Check_Mode = Minimized
            or else (Top_Level and not Bignum_Operands)
          then
-            Enable_Overflow_Check (N);
+            if Do_Overflow_Check (N) then
+               Enable_Overflow_Check (N);
+            end if;
 
-            --  Since we are doing an overflow check, the result has to be in
-            --  Long_Long_Integer mode, so adjust the possible range to reflect
-            --  this. Note these calls also change No_Uint values from the top
-            --  level case to LLI bounds.
+            --  The result now has to be in Long_Long_Integer mode, so adjust
+            --  the possible range to reflect this. Note these calls also
+            --  change No_Uint values from the top level case to LLI bounds.
 
             Max (Lo, LLLo);
             Min (Hi, LLHi);
@@ -7500,7 +7545,7 @@ package body Checks is
                  Make_Function_Call (Loc,
                    Name                   => New_Occurrence_Of (Fent, Loc),
                    Parameter_Associations => Args));
-               Analyze_And_Resolve (N, RTE (RE_Bignum));
+               Reanalyze (RTE (RE_Bignum), Suppress => True);
 
                --  Indicate result is Bignum mode
 
@@ -7557,48 +7602,36 @@ package body Checks is
       --  we will complete any division checks (since we have not changed the
       --  setting of the Do_Division_Check flag).
 
-      --  If no overflow check, suppress overflow check to avoid an infinite
-      --  recursion into this procedure.
+      --  We do this reanalysis in STRICT mode to avoid recursion into the
+      --  MINIMIZED/ELIMINATED handling, since we are now done with that!
 
-      if not Do_Overflow_Check (N) then
-         Analyze_And_Resolve (N, LLIB, Suppress => Overflow_Check);
+      declare
+         SG : constant Overflow_Check_Type :=
+                Scope_Suppress.Overflow_Checks_General;
+         SA : constant Overflow_Check_Type :=
+                Scope_Suppress.Overflow_Checks_Assertions;
 
-      --  If an overflow check is required, do it in normal CHECKED mode.
-      --  That avoids an infinite recursion, making sure we get a normal
-      --  overflow check.
+      begin
+         Scope_Suppress.Overflow_Checks_General    := Strict;
+         Scope_Suppress.Overflow_Checks_Assertions := Strict;
 
-      else
-         declare
-            SG : constant Overflow_Check_Type :=
-                   Scope_Suppress.Overflow_Checks_General;
-            SA : constant Overflow_Check_Type :=
-                   Scope_Suppress.Overflow_Checks_Assertions;
-         begin
-            Scope_Suppress.Overflow_Checks_General    := Checked;
-            Scope_Suppress.Overflow_Checks_Assertions := Checked;
-            Analyze_And_Resolve (N, LLIB);
-            Scope_Suppress.Overflow_Checks_General    := SG;
-            Scope_Suppress.Overflow_Checks_Assertions := SA;
-         end;
-      end if;
-   end Minimize_Eliminate_Overflow_Checks;
+         if not Do_Overflow_Check (N) then
+            Reanalyze (LLIB, Suppress => True);
+         else
+            Reanalyze (LLIB);
+         end if;
+
+         Scope_Suppress.Overflow_Checks_General    := SG;
+         Scope_Suppress.Overflow_Checks_Assertions := SA;
+      end;
+   end Minimize_Eliminate_Overflows;
 
    -------------------------
    -- Overflow_Check_Mode --
    -------------------------
 
-   function Overflow_Check_Mode (E : Entity_Id) return Overflow_Check_Type is
+   function Overflow_Check_Mode return Overflow_Check_Type is
    begin
-      --  Check overflow suppressed on entity
-
-      if Present (E) and then Checks_May_Be_Suppressed (E) then
-         if Is_Check_Suppressed (E, Overflow_Check) then
-            return Suppressed;
-         end if;
-      end if;
-
-      --  Else return appropriate scope setting
-
       if In_Assertion_Expr = 0 then
          return Scope_Suppress.Overflow_Checks_General;
       else
@@ -7612,7 +7645,11 @@ package body Checks is
 
    function Overflow_Checks_Suppressed (E : Entity_Id) return Boolean is
    begin
-      return Overflow_Check_Mode (E) = Suppressed;
+      if Present (E) and then Checks_May_Be_Suppressed (E) then
+         return Is_Check_Suppressed (E, Overflow_Check);
+      else
+         return Scope_Suppress.Suppress (Overflow_Check);
+      end if;
    end Overflow_Checks_Suppressed;
 
    -----------------------------
diff --git a/gcc/ada/checks.ads b/gcc/ada/checks.ads
index f7a4399386d..f2919e2ad60 100644
--- a/gcc/ada/checks.ads
+++ b/gcc/ada/checks.ads
@@ -72,12 +72,11 @@ package Checks is
    --  determine whether check C is suppressed either on the entity E or
    --  as the result of a scope suppress pragma. If Checks_May_Be_Suppressed
    --  is False, then the status of the check can be determined simply by
-   --  examining Scope_Checks (C), so this routine is not called in that case.
+   --  examining Scope_Suppress, so this routine is not called in that case.
 
-   function Overflow_Check_Mode (E : Entity_Id) return Overflow_Check_Type;
+   function Overflow_Check_Mode return Overflow_Check_Type;
    --  Returns current overflow checking mode, taking into account whether
-   --  we are inside an assertion expression. Always returns Suppressed if
-   --  overflow checks are suppressed for entity E.
+   --  we are inside an assertion expression.
 
    -------------------------------------------
    -- Procedures to Activate Checking Flags --
@@ -142,7 +141,10 @@ package Checks is
    --  overflow checking for dependent expressions. This routine handles
    --  front end vs back end overflow checks (in the front end case it expands
    --  the necessary check). Note that divide is handled separately using
-   --  Apply_Divide_Checks.
+   --  Apply_Divide_Checks. Node N may or may not have Do_Overflow_Check.
+   --  In STRICT mode, there is nothing to do if this flag is off, but in
+   --  MINIMIZED/ELIMINATED mode we still have to deal with possible use
+   --  of doing operations in Long_Long_Integer or Bignum mode.
 
    procedure Apply_Constraint_Check
      (N          : Node_Id;
@@ -266,15 +268,16 @@ package Checks is
    --  Insert_Action of the whole block (it is returned unanalyzed). The Loc
    --  parameter is used to supply Sloc values for the constructed tree.
 
-   procedure Minimize_Eliminate_Overflow_Checks
+   procedure Minimize_Eliminate_Overflows
      (N         : Node_Id;
       Lo        : out Uint;
       Hi        : out Uint;
       Top_Level : Boolean);
    --  This is the main routine for handling MINIMIZED and ELIMINATED overflow
-   --  checks. On entry N is a node whose result is a signed integer subtype.
-   --  If the node is an arithmetic operation, then a range analysis is carried
-   --  out, and there are three possibilities:
+   --  processing. On entry N is a node whose result is a signed integer
+   --  subtype. The Do_Overflow_Check flag may or may not be set on N. If the
+   --  node is an arithmetic operation, then a range analysis is carried out,
+   --  and there are three possibilities:
    --
    --    The node is left unchanged (apart from expansion of an exponentiation
    --    operation). This happens if the routine can determine that the result
@@ -313,16 +316,16 @@ package Checks is
    --  The routine is called in three situations if we are operating in either
    --  MINIMIZED or ELIMINATED modes.
    --
-   --    Overflow checks applied to the top node of an expression tree when
+   --    Overflow processing applied to the top node of an expression tree when
    --    that node is an arithmetic operator. In this case the result is
    --    converted to the appropriate result type (there is special processing
    --    when the parent is a conversion, see body for details).
    --
-   --    Overflow checks are applied to the operands of a comparison operation.
+   --    Overflow processing applied to the operands of a comparison operation.
    --    In this case, the comparison is done on the result Long_Long_Integer
    --    or Bignum values, without raising any exceptions.
    --
-   --    Overflow checks are applied to the left operand of a membership test.
+   --    Overflow processing applied to the left operand of a membership test.
    --    In this case no exception is raised if a Long_Long_Integer or Bignum
    --    result is outside the range of the type of that left operand (it is
    --    just that the result of IN is false in that case).
@@ -332,13 +335,13 @@ package Checks is
    --
    --  Top_Level is used to avoid inefficient unnecessary transitions into the
    --  Bignum domain. If Top_Level is True, it means that the caller will have
-   --  to convert any Bignum value back to Long_Long_Integer, checking that the
-   --  value is in range. This is the normal case for a top level operator in
-   --  a subexpression. There is no point in going into Bignum mode to avoid an
-   --  overflow just so we can check for overflow the next moment. For calls
-   --  from comparisons and membership tests, and for all recursive calls, we
-   --  do want to transition into the Bignum domain if necessary. Note that
-   --  this setting is only relevant in ELIMINATED mode.
+   --  to convert any Bignum value back to Long_Long_Integer, possibly checking
+   --  that the value is in range. This is the normal case for a top level
+   --  operator in a subexpression. There is no point in going into Bignum mode
+   --  to avoid an overflow just so we can check for overflow the next moment.
+   --  For calls from comparisons and membership tests, and for all recursive
+   --  calls, we do want to transition into the Bignum domain if necessary.
+   --  Note that this setting is only relevant in ELIMINATED mode.
 
    -------------------------------------------------------
    -- Control and Optimization of Range/Overflow Checks --
@@ -370,9 +373,7 @@ package Checks is
    --  has no effect. If a check is needed then this routine sets the flag
    --  Do_Overflow_Check in node N to True, unless it can be determined that
    --  the check is not needed. The only condition under which this is the
-   --  case is if there was an identical check earlier on. These optimziations
-   --  apply to CHECKED mode, but not to MINIMIZED/ELIMINATED modes. See the
-   --  body for a full explanation.
+   --  case is if there was an identical check earlier on.
 
    procedure Enable_Range_Check (N : Node_Id);
    --  Set Do_Range_Check flag in node N True, unless it can be determined
diff --git a/gcc/ada/exp_ch4.adb b/gcc/ada/exp_ch4.adb
index d9bdebd2900..f62d70d1fca 100644
--- a/gcc/ada/exp_ch4.adb
+++ b/gcc/ada/exp_ch4.adb
@@ -213,19 +213,19 @@ package body Exp_Ch4 is
    --  Convert_To_Actual_Subtype if necessary).
 
    function Minimized_Eliminated_Overflow_Check (N : Node_Id) return Boolean;
-   --  For signed arithmetic operations with Do_Overflow_Check set when the
-   --  current overflow mode is MINIMIZED or ELIMINATED, we need to make a
-   --  call to Apply_Arithmetic_Overflow_Checks as the first thing we do. We
-   --  then return. We count on the recursive apparatus for overflow checks
-   --  to call us back with an equivalent operation that does not have the
-   --  Do_Overflow_Check flag set, and that is when we will proceed with the
-   --  expansion of the operator (e.g. converting X+0 to X, or X**2 to X*X).
-   --  We cannot do these optimizations without first making this check, since
-   --  there may be operands further down the tree that are relying on the
-   --  recursive calls triggered by the top level nodes to properly process
-   --  overflow checking and remaining expansion on these nodes. Note that
-   --  this call back may be skipped if the operation is done in Bignum mode
-   --  but that's fine, since the Bignum call takes care of everything.
+   --  For signed arithmetic operations when the current overflow mode is
+   --  MINIMIZED or ELIMINATED, we must call Apply_Arithmetic_Overflow_Checks
+   --  as the first thing we do. We then return. We count on the recursive
+   --  apparatus for overflow checks to call us back with an equivalent
+   --  operation that is in CHECKED mode, avoiding a recursive entry into this
+   --  routine, and that is when we will proceed with the expansion of the
+   --  operator (e.g. converting X+0 to X, or X**2 to X*X). We cannot do
+   --  these optimizations without first making this check, since there may be
+   --  operands further down the tree that are relying on the recursive calls
+   --  triggered by the top level nodes to properly process overflow checking
+   --  and remaining expansion on these nodes. Note that this call back may be
+   --  skipped if the operation is done in Bignum mode but that's fine, since
+   --  the Bignum call takes care of everything.
 
    procedure Optimize_Length_Comparison (N : Node_Id);
    --  Given an expression, if it is of the form X'Length op N (or the other
@@ -2274,8 +2274,8 @@ package body Exp_Ch4 is
       LLIB : constant Entity_Id := Base_Type (Standard_Long_Long_Integer);
       --  Entity for Long_Long_Integer'Base
 
-      Check : constant Overflow_Check_Type := Overflow_Check_Mode (Empty);
-      --  Current checking mode
+      Check : constant Overflow_Check_Type := Overflow_Check_Mode;
+      --  Current overflow checking mode
 
       procedure Set_True;
       procedure Set_False;
@@ -2320,9 +2320,9 @@ package body Exp_Ch4 is
       --  our operands using the Minimize_Eliminate circuitry which applies
       --  this processing to the two operand subtrees.
 
-      Minimize_Eliminate_Overflow_Checks
+      Minimize_Eliminate_Overflows
         (Left_Opnd (N),  Llo, Lhi, Top_Level => False);
-      Minimize_Eliminate_Overflow_Checks
+      Minimize_Eliminate_Overflows
         (Right_Opnd (N), Rlo, Rhi, Top_Level => False);
 
       --  See if the range information decides the result of the comparison.
@@ -3721,7 +3721,7 @@ package body Exp_Ch4 is
       --  Entity for Long_Long_Integer'Base (Standard should export this???)
 
    begin
-      Minimize_Eliminate_Overflow_Checks (Lop, Lo, Hi, Top_Level => False);
+      Minimize_Eliminate_Overflows (Lop, Lo, Hi, Top_Level => False);
 
       --  If right operand is a subtype name, and the subtype name has no
       --  predicate, then we can just replace the right operand with an
@@ -3751,9 +3751,9 @@ package body Exp_Ch4 is
       --  have not been processed for minimized or eliminated checks.
 
       if Nkind (Rop) = N_Range then
-         Minimize_Eliminate_Overflow_Checks
+         Minimize_Eliminate_Overflows
            (Low_Bound (Rop), Lo, Hi, Top_Level => False);
-         Minimize_Eliminate_Overflow_Checks
+         Minimize_Eliminate_Overflows
            (High_Bound (Rop), Lo, Hi, Top_Level => False);
 
          --  We have A in B .. C, treated as  A >= B and then A <= C
@@ -5498,7 +5498,7 @@ package body Exp_Ch4 is
          --  in which case, this usage makes sense, and in any case, we have
          --  actually eliminated the danger of optimization above.
 
-         if Overflow_Check_Mode (Restyp) not in Minimized_Or_Eliminated then
+         if Overflow_Check_Mode not in Minimized_Or_Eliminated then
             Error_Msg_N ("?explicit membership test may be optimized away", N);
             Error_Msg_N -- CODEFIX
               ("\?use ''Valid attribute instead", N);
@@ -5526,7 +5526,7 @@ package body Exp_Ch4 is
       --  type, then expand with a separate procedure. Note the use of the
       --  flag No_Minimize_Eliminate to prevent infinite recursion.
 
-      if Overflow_Check_Mode (Empty) in Minimized_Or_Eliminated
+      if Overflow_Check_Mode in Minimized_Or_Eliminated
         and then Is_Signed_Integer_Type (Ltyp)
         and then not No_Minimize_Eliminate (N)
       then
@@ -11785,8 +11785,7 @@ package body Exp_Ch4 is
    begin
       return
         Is_Signed_Integer_Type (Etype (N))
-          and then Do_Overflow_Check (N)
-          and then Overflow_Check_Mode (Empty) in Minimized_Or_Eliminated;
+          and then Overflow_Check_Mode in Minimized_Or_Eliminated;
    end Minimized_Eliminated_Overflow_Check;
 
    --------------------------------
diff --git a/gcc/ada/exp_util.adb b/gcc/ada/exp_util.adb
index cc3213d03da..7c1ceeb8f7e 100644
--- a/gcc/ada/exp_util.adb
+++ b/gcc/ada/exp_util.adb
@@ -3840,11 +3840,11 @@ package body Exp_Util is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Sva : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Insert_Actions (Assoc_Node, Ins_Actions);
-            Scope_Suppress := Svg;
+            Scope_Suppress.Suppress := Sva;
          end;
 
       else
@@ -6727,7 +6727,7 @@ package body Exp_Util is
 
       --  All this must not have any checks
 
-      Scope_Suppress := Suppress_All;
+      Scope_Suppress.Suppress := (others => True);
 
       --  If it is a scalar type and we need to capture the value, just make
       --  a copy. Likewise for a function call, an attribute reference, an
diff --git a/gcc/ada/gnat1drv.adb b/gcc/ada/gnat1drv.adb
index 47c4b177f01..ee6ca097e78 100644
--- a/gcc/ada/gnat1drv.adb
+++ b/gcc/ada/gnat1drv.adb
@@ -192,14 +192,12 @@ procedure Gnat1drv is
 
          --  Enable all other language checks
 
-         Suppress_Options :=
-           (Suppress                   => (Access_Check      => True,
-                                           Alignment_Check   => True,
-                                           Division_Check    => True,
-                                           Elaboration_Check => True,
-                                           others            => False),
-            Overflow_Checks_General    => Suppressed,
-            Overflow_Checks_Assertions => Suppressed);
+         Suppress_Options.Suppress :=
+           (Access_Check      => True,
+            Alignment_Check   => True,
+            Division_Check    => True,
+            Elaboration_Check => True,
+            others            => False);
 
          Dynamic_Elaboration_Checks := False;
 
@@ -328,42 +326,50 @@ procedure Gnat1drv is
          Exception_Mechanism := Back_End_Exceptions;
       end if;
 
-      --  Set proper status for overflow checks
+      --  Set proper status for overflow check mechanism
 
-      --  If already set (by - gnato or -gnatp) then we have nothing to do
+      --  If already set (by -gnato) then we have nothing to do
 
       if Opt.Suppress_Options.Overflow_Checks_General /= Not_Set then
          null;
 
-      --  Otherwise set appropriate default mode. Note: at present we set
-      --  SUPPRESSED in all three of the following cases. They are separated
-      --  because in the future we may make different choices.
+      --  Otherwise set overflow mode defaults
 
-      --  By default suppress overflow checks in -gnatg mode
+      else
+         --  Otherwise set overflow checks off by default
 
-      elsif GNAT_Mode then
-         Suppress_Options.Overflow_Checks_General    := Suppressed;
-         Suppress_Options.Overflow_Checks_Assertions := Suppressed;
+         Suppress_Options.Suppress (Overflow_Check) := True;
 
-      --  If we have backend divide and overflow checks, then by default
-      --  overflow checks are suppressed. Historically this code used to
-      --  activate overflow checks, although no target currently has these
-      --  flags set, so this was dead code anyway.
+         --  Set appropriate default overflow handling mode. Note: at present
+         --  we set STRICT in all three of the following cases. They are
+         --  separated because in the future we may make different choices.
 
-      elsif Targparm.Backend_Divide_Checks_On_Target
-              and
-            Targparm.Backend_Overflow_Checks_On_Target
-      then
-         Suppress_Options.Overflow_Checks_General    := Suppressed;
-         Suppress_Options.Overflow_Checks_Assertions := Suppressed;
+         --  By default set STRICT mode if -gnatg in effect
 
-      --  Otherwise for now, default is checks are suppressed. This is subject
-      --  to change in the future, but for now this is the compatible behavior
-      --  with previous versions of GNAT.
+         if GNAT_Mode then
+            Suppress_Options.Overflow_Checks_General    := Strict;
+            Suppress_Options.Overflow_Checks_Assertions := Strict;
 
-      else
-         Suppress_Options.Overflow_Checks_General    := Suppressed;
-         Suppress_Options.Overflow_Checks_Assertions := Suppressed;
+         --  If we have backend divide and overflow checks, then by default
+         --  overflow checks are STRICT. Historically this code used to also
+         --  activate overflow checks, although no target currently has these
+         --  flags set, so this was dead code anyway.
+
+         elsif Targparm.Backend_Divide_Checks_On_Target
+           and
+             Targparm.Backend_Overflow_Checks_On_Target
+         then
+            Suppress_Options.Overflow_Checks_General    := Strict;
+            Suppress_Options.Overflow_Checks_Assertions := Strict;
+
+         --  Otherwise for now, default is STRICT mode. This may change in the
+         --  future, but for now this is the compatible behavior with previous
+         --  versions of GNAT.
+
+         else
+            Suppress_Options.Overflow_Checks_General    := Strict;
+            Suppress_Options.Overflow_Checks_Assertions := Strict;
+         end if;
       end if;
 
       --  Set default for atomic synchronization. As this synchronization
diff --git a/gcc/ada/sem.adb b/gcc/ada/sem.adb
index 6aafad8e059..f3577790f4c 100644
--- a/gcc/ada/sem.adb
+++ b/gcc/ada/sem.adb
@@ -723,29 +723,15 @@ package body Sem is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Svs : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Analyze (N);
-            Scope_Suppress := Svg;
+            Scope_Suppress.Suppress := Svs;
          end;
 
       elsif Suppress = Overflow_Check then
          declare
-            Svg : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_General;
-            Sva : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_Assertions;
-         begin
-            Scope_Suppress.Overflow_Checks_General    := Suppressed;
-            Scope_Suppress.Overflow_Checks_Assertions := Suppressed;
-            Analyze (N);
-            Scope_Suppress.Overflow_Checks_General    := Svg;
-            Scope_Suppress.Overflow_Checks_Assertions := Sva;
-         end;
-
-      else
-         declare
             Svg : constant Boolean := Scope_Suppress.Suppress (Suppress);
          begin
             Scope_Suppress.Suppress (Suppress) := True;
@@ -776,25 +762,11 @@ package body Sem is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
-         begin
-            Scope_Suppress := Suppress_All;
-            Analyze_List (L);
-            Scope_Suppress := Svg;
-         end;
-
-      elsif Suppress = Overflow_Check then
-         declare
-            Svg : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_General;
-            Sva : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_Assertions;
+            Svs : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress.Overflow_Checks_General    := Suppressed;
-            Scope_Suppress.Overflow_Checks_Assertions := Suppressed;
+            Scope_Suppress.Suppress := (others => True);
             Analyze_List (L);
-            Scope_Suppress.Overflow_Checks_General    := Svg;
-            Scope_Suppress.Overflow_Checks_Assertions := Sva;
+            Scope_Suppress.Suppress := Svs;
          end;
 
       else
@@ -1051,11 +1023,11 @@ package body Sem is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Svs : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Insert_After_And_Analyze (N, M);
-            Scope_Suppress := Svg;
+            Scope_Suppress.Suppress := Svs;
          end;
 
       else
@@ -1111,11 +1083,11 @@ package body Sem is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Svs : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Insert_Before_And_Analyze (N, M);
-            Scope_Suppress := Svg;
+            Scope_Suppress.Suppress := Svs;
          end;
 
       else
@@ -1170,11 +1142,11 @@ package body Sem is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Svs : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Insert_List_After_And_Analyze (N, L);
-            Scope_Suppress := Svg;
+            Scope_Suppress.Suppress := Svs;
          end;
 
       else
@@ -1228,11 +1200,11 @@ package body Sem is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Svs : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Insert_List_Before_And_Analyze (N, L);
-            Scope_Suppress := Svg;
+            Scope_Suppress.Suppress := Svs;
          end;
 
       else
diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
index f7f56f01e0a..4ca5285d7ef 100644
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -2121,7 +2121,8 @@ package body Sem_Prag is
               (Get_Pragma_Arg (Arg2), Standard_String);
          end if;
 
-         --  Record if pragma is disabled
+         --  For a pragma in the extended main source unit, record enabled
+         --  status in SCO (note: there is never any SCO for an instance).
 
          if Check_Enabled (Pname) then
             Set_SCO_Pragma_Enabled (Loc);
@@ -5058,7 +5059,8 @@ package body Sem_Prag is
 
                   --  If previous error, avoid cascaded errors
 
-                  Applies := True;
+                  Cascaded_Error;
+                  Applies   := True;
                   Effective := True;
 
                else
@@ -5703,18 +5705,6 @@ package body Sem_Prag is
               ("argument of pragma% is not valid check name", Arg1);
          end if;
 
-         --  Special processing for overflow check case
-
-         if C = All_Checks or else C = Overflow_Check then
-            if Suppress_Case then
-               Scope_Suppress.Overflow_Checks_General    := Suppressed;
-               Scope_Suppress.Overflow_Checks_Assertions := Suppressed;
-            else
-               Scope_Suppress.Overflow_Checks_General    := Checked;
-               Scope_Suppress.Overflow_Checks_Assertions := Checked;
-            end if;
-         end if;
-
          if Arg_Count = 1 then
 
             --  Make an entry in the local scope suppress table. This is the
@@ -12007,10 +11997,11 @@ package body Sem_Prag is
          --  pragma Overflow_Checks
          --    ([General => ] MODE [, [Assertions => ] MODE]);
 
-         --  MODE := SUPPRESSED | CHECKED | MINIMIZED | ELIMINATED
+         --  MODE := STRICT | MINIMIZED | ELIMINATED
 
          --  Note: ELIMINATED is allowed only if Long_Long_Integer'Size is 64
-         --  since System.Bignums makes this assumption.
+         --  since System.Bignums makes this assumption. This is true of nearly
+         --  all (all?) targets.
 
          when Pragma_Overflow_Checks => Overflow_Checks : declare
             function Get_Check_Mode
@@ -12034,19 +12025,8 @@ package body Sem_Prag is
                Check_Optional_Identifier (Arg, Name);
                Check_Arg_Is_Identifier (Argx);
 
-               --  Do not suppress overflow checks for formal verification.
-               --  Instead, require that a check is inserted so that formal
-               --  verification can detect wraparound errors.
-
-               if Chars (Argx) = Name_Suppressed then
-                  if Alfa_Mode then
-                     return Checked;
-                  else
-                     return Suppressed;
-                  end if;
-
-               elsif Chars (Argx) = Name_Checked then
-                  return Checked;
+               if Chars (Argx) = Name_Strict then
+                  return Strict;
 
                elsif Chars (Argx) = Name_Minimized then
                   return Minimized;
@@ -14545,6 +14525,7 @@ package body Sem_Prag is
             --  Note: in previous versions of GNAT we used to check for limited
             --  types and give an error, but in fact the standard does allow
             --  Unchecked_Union on limited types, so this check was removed.
+
             --  Similarly, GNAT used to require that all discriminants have
             --  default values, but this is not mandated by the RM.
 
diff --git a/gcc/ada/sem_res.adb b/gcc/ada/sem_res.adb
index 847dd30c126..64199fa2cf6 100644
--- a/gcc/ada/sem_res.adb
+++ b/gcc/ada/sem_res.adb
@@ -334,25 +334,11 @@ package body Sem_Res is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Sva : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Analyze_And_Resolve (N, Typ);
-            Scope_Suppress := Svg;
-         end;
-
-      elsif Suppress = Overflow_Check then
-         declare
-            Svg : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_General;
-            Sva : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_Assertions;
-         begin
-            Scope_Suppress.Overflow_Checks_General    := Suppressed;
-            Scope_Suppress.Overflow_Checks_Assertions := Suppressed;
-            Analyze_And_Resolve (N, Typ);
-            Scope_Suppress.Overflow_Checks_General    := Svg;
-            Scope_Suppress.Overflow_Checks_Assertions := Sva;
+            Scope_Suppress.Suppress := Sva;
          end;
 
       else
@@ -388,25 +374,11 @@ package body Sem_Res is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
-         begin
-            Scope_Suppress := Suppress_All;
-            Analyze_And_Resolve (N);
-            Scope_Suppress := Svg;
-         end;
-
-      elsif Suppress = Overflow_Check then
-         declare
-            Svg : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_General;
-            Sva : constant Overflow_Check_Type :=
-                    Scope_Suppress.Overflow_Checks_Assertions;
+            Sva : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress.Overflow_Checks_General    := Suppressed;
-            Scope_Suppress.Overflow_Checks_Assertions := Suppressed;
+            Scope_Suppress.Suppress := (others => True);
             Analyze_And_Resolve (N);
-            Scope_Suppress.Overflow_Checks_General    := Svg;
-            Scope_Suppress.Overflow_Checks_Assertions := Sva;
+            Scope_Suppress.Suppress := Sva;
          end;
 
       else
@@ -1690,19 +1662,23 @@ package body Sem_Res is
       Full_Analysis := False;
       Expander_Mode_Save_And_Set (False);
 
-      --  We suppress all checks for this analysis, except in Alfa mode.
-      --  Otherwise the checks are applied properly, and in the proper
-      --  location, when the default expressions are reanalyzed and reexpanded
-      --  later on.
+      --  Normally, we suppress all checks for this preanalysis. There is no
+      --  point in processing them now, since they will be applied properly
+      --  and in the proper location when the default expressions reanalyzed
+      --  and reexpanded later on. We will also have more information at that
+      --  point for possible suppression of individual checks.
 
-      --  Alfa mode suppresses all expansion but requires the setting of
-      --  checking flags (DIvision_Check and others) in particular for Ada 2012
-      --  constructs such as quantified expressions, that are expanded in two
-      --  separate steps.
+      --  However, in Alfa mode, most expansion is suppressed, and this
+      --  later reanalysis and reexpansion may not occur. Alfa mode does
+      --  require the setting of checking flags for proof purposes, so we
+      --  do the Alfa preanalysis without suppressing checks.
+
+      --  This special handling for Alfa mode is required for example in the
+      --  case of Ada 2012 constructs such as quantified expressions, which are
+      --  expanded in two separate steps.
 
       if Alfa_Mode then
          Analyze_And_Resolve (N, T);
-
       else
          Analyze_And_Resolve (N, T, Suppress => All_Checks);
       end if;
@@ -2946,11 +2922,11 @@ package body Sem_Res is
    begin
       if Suppress = All_Checks then
          declare
-            Svg : constant Suppress_Record := Scope_Suppress;
+            Sva : constant Suppress_Array := Scope_Suppress.Suppress;
          begin
-            Scope_Suppress := Suppress_All;
+            Scope_Suppress.Suppress := (others => True);
             Resolve (N, Typ);
-            Scope_Suppress := Svg;
+            Scope_Suppress.Suppress := Sva;
          end;
 
       else
@@ -5959,16 +5935,6 @@ package body Sem_Res is
 
       Set_Etype (N, Typ);
       Eval_Case_Expression (N);
-
-      --  If we still have a case expression, and overflow checks are enabled
-      --  in MINIMIZED or ELIMINATED modes, then set Do_Overflow_Check to
-      --  ensure that we handle overflow for dependent expressions.
-
-      if Nkind (N) = N_Case_Expression
-        and then Overflow_Check_Mode (Typ) in Minimized_Or_Eliminated
-      then
-         Set_Do_Overflow_Check (N);
-      end if;
    end Resolve_Case_Expression;
 
    -------------------------------
@@ -7215,16 +7181,6 @@ package body Sem_Res is
 
       Set_Etype (N, Typ);
       Eval_If_Expression (N);
-
-      --  If we still have a if expression, and overflow checks are enabled in
-      --  MINIMIZED or ELIMINATED modes, then set Do_Overflow_Check to ensure
-      --  that we handle overflow for dependent expressions.
-
-      if Nkind (N) = N_If_Expression
-        and then Overflow_Check_Mode (Typ) in Minimized_Or_Eliminated
-      then
-         Set_Do_Overflow_Check (N);
-      end if;
    end Resolve_If_Expression;
 
    -------------------------------
diff --git a/gcc/ada/snames.ads-tmpl b/gcc/ada/snames.ads-tmpl
index 864d8ed12c4..efd340f01d6 100644
--- a/gcc/ada/snames.ads-tmpl
+++ b/gcc/ada/snames.ads-tmpl
@@ -665,7 +665,6 @@ package Snames is
    Name_By_Protected_Procedure         : constant Name_Id := N + $;
    Name_Casing                         : constant Name_Id := N + $;
    Name_Check_All                      : constant Name_Id := N + $;
-   Name_Checked                        : constant Name_Id := N + $;
    Name_Code                           : constant Name_Id := N + $;
    Name_Component                      : constant Name_Id := N + $;
    Name_Component_Size_4               : constant Name_Id := N + $;
@@ -739,6 +738,7 @@ package Snames is
    Name_State                          : constant Name_Id := N + $;
    Name_Static                         : constant Name_Id := N + $;
    Name_Stack_Size                     : constant Name_Id := N + $;
+   Name_Strict                         : constant Name_Id := N + $;
    Name_Subunit_File_Name              : constant Name_Id := N + $;
    Name_Suppressed                     : constant Name_Id := N + $;
    Name_Task_Stack_Size_Default        : constant Name_Id := N + $;
diff --git a/gcc/ada/switch-c.adb b/gcc/ada/switch-c.adb
index 2a96c06d11a..e7d517e794e 100644
--- a/gcc/ada/switch-c.adb
+++ b/gcc/ada/switch-c.adb
@@ -97,11 +97,8 @@ package body Switch.C is
    function Get_Overflow_Mode (C : Character) return Overflow_Check_Type is
    begin
       case C is
-         when '0' =>
-            return Suppressed;
-
          when '1' =>
-            return Checked;
+            return Strict;
 
          when '2' =>
             return Minimized;
@@ -801,12 +798,13 @@ package body Switch.C is
 
             when 'o' =>
                Ptr := Ptr + 1;
+               Suppress_Options.Suppress (Overflow_Check) := False;
 
                --  Case of no digits after the -gnato
 
-               if Ptr > Max or else Switch_Chars (Ptr) not in '0' .. '3' then
-                  Suppress_Options.Overflow_Checks_General    := Checked;
-                  Suppress_Options.Overflow_Checks_Assertions := Checked;
+               if Ptr > Max or else Switch_Chars (Ptr) not in '1' .. '3' then
+                  Suppress_Options.Overflow_Checks_General    := Strict;
+                  Suppress_Options.Overflow_Checks_Assertions := Strict;
 
                --  At least one digit after the -gnato
 
@@ -821,7 +819,7 @@ package body Switch.C is
                   --  be the same as general mode.
 
                   if Ptr > Max
-                    or else Switch_Chars (Ptr) not in '0' .. '3'
+                    or else Switch_Chars (Ptr) not in '1' .. '3'
                   then
                      Suppress_Options.Overflow_Checks_Assertions :=
                        Suppress_Options.Overflow_Checks_General;
@@ -869,9 +867,6 @@ package body Switch.C is
                      end if;
                   end loop;
 
-                  Suppress_Options.Overflow_Checks_General    := Suppressed;
-                  Suppress_Options.Overflow_Checks_Assertions := Suppressed;
-
                   Validity_Checks_On  := False;
                   Opt.Suppress_Checks := True;
                end if;
diff --git a/gcc/ada/types.ads b/gcc/ada/types.ads
index 277bfd55146..861c0bcc1c8 100644
--- a/gcc/ada/types.ads
+++ b/gcc/ada/types.ads
@@ -703,43 +703,39 @@ package Types is
    --    4.  Add a new Do_xxx_Check flag to Sinfo (if required)
    --    5.  Add appropriate checks for the new test
 
-   --  The following provides precise details on the mode used to check
-   --  intermediate overflows in expressions for signed integer arithmetic.
+   --  The following provides precise details on the mode used to generate
+   --  code for intermediate overflows in expressions for signed integer
+   --  arithmetic (and how to generate overflow checks if enabled). Note
+   --  that this only affects handling of intermediate results. The final
+   --  result must always fit within the target range, and if overflow
+   --  checking is enabled, the check on the final result is against this
+   --  target range.
 
    type Overflow_Check_Type is (
       Not_Set,
       --  Dummy value used during initialization process to show that the
       --  corresponding value has not yet been initialized.
 
-      Suppressed,
-      --  Overflow checking is suppressed. If an arithmetic operation creates
-      --  an overflow, no exception is raised, and the program is erroneous.
-
-      Checked,
-      --  All operations, including all intermediate operations are checked.
-      --  If the result of any arithmetic operation gives a result outside the
-      --  range of the base type, then a Constraint_Error exception is raised.
+      Strict,
+      --  Operations are done in the base type of the subexpression. If
+      --  overflow checks are enabled, then the check is against the range
+      --  of this base type.
 
       Minimized,
-      --  Where appropriate, arithmetic operations are performed with an
-      --  extended range, using Long_Long_Integer if necessary. As long as the
-      --  result fits in this extended range, then no exception is raised and
-      --  computation continues with the extended result. The final value of an
-      --  expression must fit in the base type of the whole expression. If an
-      --  intermediate result is outside the range of Long_Long_Integer then a
-      --  Constraint_Error exception is raised.
+      --  Where appropriate, intermediate arithmetic operations are performed
+      --  with an extended range, using Long_Long_Integer if necessary. If
+      --  overflow checking is enabled, then the check is against the range
+      --  of Long_Long_Integer.
 
       Eliminated);
       --  In this mode arbitrary precision arithmetic is used as needed to
       --  ensure that it is impossible for intermediate arithmetic to cause an
-      --  overflow. Again the final value of an expression must fit in the base
-      --  type of the whole expression.
+      --  overflow. In this mode, intermediate expressions are not affected by
+      --  the overflow checking mode, since overflows are eliminated.
 
    subtype Minimized_Or_Eliminated is
      Overflow_Check_Type range Minimized .. Eliminated;
-   subtype Suppressed_Or_Checked is
-     Overflow_Check_Type range Suppressed .. Checked;
-   --  Define subtypes so that clients don't need to know ordering. Note that
+   --  Define subtype so that clients don't need to know ordering. Note that
    --  Overflow_Check_Type is not marked as an ordered enumeration type.
 
    --  The following structure captures the state of check suppression or
@@ -747,24 +743,19 @@ package Types is
 
    type Suppress_Record is record
       Suppress : Suppress_Array;
-      --  Indicates suppression status of each possible check. Note: there
-      --  is an entry for Overflow_Check in this array, but it is never used.
-      --  Instead we use the more detailed information in the two components
-      --  that follow this one (Overflow_Checks_General/Assertions).
+      --  Indicates suppression status of each possible check
 
       Overflow_Checks_General : Overflow_Check_Type;
-      --  This field indicates the mode of overflow checking to be applied to
-      --  general expressions outside assertions.
+      --  This field indicates the mode for handling code generation and
+      --  overflow checking (if enabled) for intermediate expression values.
+      --  This applies to general expressions outside assertions.
 
       Overflow_Checks_Assertions : Overflow_Check_Type;
-      --  This field indicates the mode of overflow checking to be applied to
-      --  any expression occuring inside assertions.
+      --  This field indicates the mode for handling code generation and
+      --  overflow checking (if enabled) for intermediate expression values.
+      --  This applies to any expression occuring inside assertions.
    end record;
 
-   Suppress_All : constant Suppress_Record :=
-                    ((others => True), Suppressed, Suppressed);
-   --  Constant used to initialize Suppress_Record value to all suppressed.
-
    -----------------------------------
    -- Global Exception Declarations --
    -----------------------------------