diff --git a/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst b/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst
index 7968073a985..2838a302f2e 100644
--- a/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst
+++ b/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst
@@ -4706,7 +4706,7 @@ Style Checking
 
 .. index:: -gnaty  (gcc)
 
-The :switch:`-gnatyx` switch causes the compiler to
+The :switch:`-gnaty` switch causes the compiler to
 enforce specified style rules. A limited set of style rules has been used
 in writing the GNAT sources themselves. This switch allows user programs
 to activate all or some of these checks. If the source program fails a
@@ -4904,9 +4904,9 @@ checks to be performed. The following checks are defined:
 
   The set of style check switches is set to match that used by the GNAT sources.
   This may be useful when developing code that is eventually intended to be
-  incorporated into GNAT. Currently this is equivalent to :switch:`-gnatyydISux`)
-  but additional style switches may be added to this set in the future without
-  advance notice.
+  incorporated into GNAT. Currently this is equivalent to
+  :switch:`-gnatyydISuxz`) but additional style switches may be added to this
+  set in the future without advance notice.
 
 
 .. index:: -gnatyh (gcc)
@@ -5207,9 +5207,9 @@ checks to be performed. The following checks are defined:
 :switch:`-gnatyx`
   *Check extra parentheses.*
 
-  Unnecessary extra level of parentheses (C-style) are not allowed
-  around conditions in ``if`` statements, ``while`` statements and
-  ``exit`` statements.
+  Unnecessary extra levels of parentheses (C-style) are not allowed
+  around conditions (or selection expressions) in ``if``, ``while``,
+  ``case``, and ``exit`` statements, as well as part of ranges.
 
 
 .. index:: -gnatyy (gcc)
@@ -5223,6 +5223,15 @@ checks to be performed. The following checks are defined:
   :switch:`-gnatyS`, :switch:`-gnatyu`, and :switch:`-gnatyx`.
 
 
+.. index:: -gnatyz (gcc)
+
+:switch:`-gnatyz`
+  *Check extra parentheses (operator precedence).*
+
+  Extra levels of parentheses that are not required by operator precedence
+  rules are flagged. See also ``-gnatyx``.
+
+
 .. index:: -gnaty- (gcc)
 
 :switch:`-gnaty-`
diff --git a/gcc/ada/gnat_ugn.texi b/gcc/ada/gnat_ugn.texi
index b95519a8295..e1242068f56 100644
--- a/gcc/ada/gnat_ugn.texi
+++ b/gcc/ada/gnat_ugn.texi
@@ -13312,7 +13312,7 @@ temporary disabling of validity checks.
 
 @geindex -gnaty (gcc)
 
-The @code{-gnatyx} switch causes the compiler to
+The @code{-gnaty} switch causes the compiler to
 enforce specified style rules. A limited set of style rules has been used
 in writing the GNAT sources themselves. This switch allows user programs
 to activate all or some of these checks. If the source program fails a
@@ -13569,9 +13569,9 @@ in the source text.
 
 The set of style check switches is set to match that used by the GNAT sources.
 This may be useful when developing code that is eventually intended to be
-incorporated into GNAT. Currently this is equivalent to @code{-gnatyydISux})
-but additional style switches may be added to this set in the future without
-advance notice.
+incorporated into GNAT. Currently this is equivalent to
+@code{-gnatyydISuxz}) but additional style switches may be added to this
+set in the future without advance notice.
 @end table
 
 @geindex -gnatyh (gcc)
@@ -13965,9 +13965,9 @@ one blank line occurs in sequence.
 
 `Check extra parentheses.'
 
-Unnecessary extra level of parentheses (C-style) are not allowed
-around conditions in @code{if} statements, @code{while} statements and
-@code{exit} statements.
+Unnecessary extra levels of parentheses (C-style) are not allowed
+around conditions (or selection expressions) in @code{if}, @code{while},
+@code{case}, and @code{exit} statements, as well as part of ranges.
 @end table
 
 @geindex -gnatyy (gcc)
@@ -13985,6 +13985,19 @@ options enabled with the exception of @code{-gnatyB}, @code{-gnatyd},
 @code{-gnatyS}, @code{-gnatyu}, and @code{-gnatyx}.
 @end table
 
+@geindex -gnatyz (gcc)
+
+
+@table @asis
+
+@item @code{-gnatyz}
+
+`Check extra parentheses (operator precedence).'
+
+Extra levels of parentheses that are not required by operator precedence
+rules are flagged. See also @code{-gnatyx}.
+@end table
+
 @geindex -gnaty- (gcc)
 
 
diff --git a/gcc/ada/libgnarl/s-interr__hwint.adb b/gcc/ada/libgnarl/s-interr__hwint.adb
index dcac8e8762e..eb2e5a20476 100644
--- a/gcc/ada/libgnarl/s-interr__hwint.adb
+++ b/gcc/ada/libgnarl/s-interr__hwint.adb
@@ -874,7 +874,7 @@ package body System.Interrupts is
               To_System (Interrupt_Access_Hold.all'Identity);
          end if;
 
-         if (New_Handler = null) and then Old_Handler /= null then
+         if New_Handler = null and then Old_Handler /= null then
 
             --  Restore default handler
 
diff --git a/gcc/ada/libgnarl/s-interr__vxworks.adb b/gcc/ada/libgnarl/s-interr__vxworks.adb
index aade352748f..93afcc583db 100644
--- a/gcc/ada/libgnarl/s-interr__vxworks.adb
+++ b/gcc/ada/libgnarl/s-interr__vxworks.adb
@@ -914,7 +914,7 @@ package body System.Interrupts is
               To_System (Interrupt_Access_Hold.all'Identity);
          end if;
 
-         if (New_Handler = null) and then Old_Handler /= null then
+         if New_Handler = null and then Old_Handler /= null then
 
             --  Restore default handler
 
diff --git a/gcc/ada/libgnat/s-regpat.adb b/gcc/ada/libgnat/s-regpat.adb
index 3d2a76c0066..80f7a8fba83 100644
--- a/gcc/ada/libgnat/s-regpat.adb
+++ b/gcc/ada/libgnat/s-regpat.adb
@@ -979,7 +979,7 @@ package body System.Regpat is
          C := Expression (Parse_Pos);
          Parse_Pos := Parse_Pos + 1;
 
-         case (C) is
+         case C is
             when '^' =>
                IP :=
                  Emit_Node
diff --git a/gcc/ada/par-ch3.adb b/gcc/ada/par-ch3.adb
index a71056b20a0..fddb1d9d163 100644
--- a/gcc/ada/par-ch3.adb
+++ b/gcc/ada/par-ch3.adb
@@ -3074,7 +3074,12 @@ package body Ch3 is
          Check_Simple_Expression (Expr_Node);
          Set_High_Bound (Range_Node, Expr_Node);
 
-         if Style_Check then
+         --  If Expr_Node (ignoring parentheses) is not a simple expression
+         --  then emit a style check.
+
+         if Style_Check
+           and then Nkind (Expr_Node) not in N_Op_Boolean | N_Subexpr
+         then
             Style.Check_Xtra_Parens (Expr_Node);
          end if;
 
diff --git a/gcc/ada/par-ch5.adb b/gcc/ada/par-ch5.adb
index 6099a78effb..bbade15c0c4 100644
--- a/gcc/ada/par-ch5.adb
+++ b/gcc/ada/par-ch5.adb
@@ -1359,7 +1359,7 @@ package body Ch5 is
 
       else
          if Style_Check then
-            Style.Check_Xtra_Parens (Cond, Enable => True);
+            Style.Check_Xtra_Parens (Cond);
          end if;
 
          --  And return the result
@@ -1384,6 +1384,7 @@ package body Ch5 is
 
    function P_Case_Statement return Node_Id is
       Case_Node         : Node_Id;
+      Expr              : Node_Id;
       Alternatives_List : List_Id;
       First_When_Loc    : Source_Ptr;
 
@@ -1398,7 +1399,14 @@ package body Ch5 is
       Scopes (Scope.Last).Node := Case_Node;
 
       Scan; -- past CASE
-      Set_Expression (Case_Node, P_Expression_No_Right_Paren);
+
+      Expr := P_Expression_No_Right_Paren;
+
+      if Style_Check then
+         Style.Check_Xtra_Parens (Expr);
+      end if;
+
+      Set_Expression (Case_Node, Expr);
       TF_Is;
 
       --  Prepare to parse case statement alternatives
diff --git a/gcc/ada/sem_ch4.adb b/gcc/ada/sem_ch4.adb
index 5b013dfb63d..a85c988fe46 100644
--- a/gcc/ada/sem_ch4.adb
+++ b/gcc/ada/sem_ch4.adb
@@ -3157,13 +3157,13 @@ package body Sem_Ch4 is
          if Nkind (L) not in N_Short_Circuit | N_Op_And | N_Op_Or | N_Op_Xor
            and then Is_Boolean_Type (Etype (L))
          then
-            Check_Xtra_Parens (L);
+            Check_Xtra_Parens_Precedence (L);
          end if;
 
          if Nkind (R) not in N_Short_Circuit | N_Op_And | N_Op_Or | N_Op_Xor
            and then Is_Boolean_Type (Etype (R))
          then
-            Check_Xtra_Parens (R);
+            Check_Xtra_Parens_Precedence (R);
          end if;
       end if;
    end Analyze_Logical_Op;
@@ -6042,12 +6042,12 @@ package body Sem_Ch4 is
       if Style_Check then
          if Nkind (L) not in N_Short_Circuit | N_Op_And | N_Op_Or | N_Op_Xor
          then
-            Check_Xtra_Parens (L);
+            Check_Xtra_Parens_Precedence (L);
          end if;
 
          if Nkind (R) not in N_Short_Circuit | N_Op_And | N_Op_Or | N_Op_Xor
          then
-            Check_Xtra_Parens (R);
+            Check_Xtra_Parens_Precedence (R);
          end if;
       end if;
    end Analyze_Short_Circuit;
diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
index ca55a6f8290..d80f78f4865 100644
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -30068,7 +30068,7 @@ package body Sem_Prag is
                                       | Name_Loop_Invariant
                                       | Name_Loop_Variant)
             then
-               case (Chars (Get_Pragma_Arg (Last (PPA)))) is
+               case Chars (Get_Pragma_Arg (Last (PPA))) is
                   when Name_Check
                      | Name_On
                   =>
diff --git a/gcc/ada/style.ads b/gcc/ada/style.ads
index 4a7faff31e3..726abcdef93 100644
--- a/gcc/ada/style.ads
+++ b/gcc/ada/style.ads
@@ -28,7 +28,6 @@
 --  gathered in a separate package so that they can more easily be customized.
 --  Calls to these subprograms are only made if Opt.Style_Check is set True.
 
-with Debug; use Debug;
 with Errout;
 with Styleg;
 with Types;    use Types;
@@ -193,10 +192,15 @@ package Style is
      renames Style_Inst.Check_Vertical_Bar;
    --  Called after scanning a vertical bar to check spacing
 
-   procedure Check_Xtra_Parens (N : Node_Id; Enable : Boolean := Debug_Flag_QQ)
+   procedure Check_Xtra_Parens (N : Node_Id)
      renames Style_Inst.Check_Xtra_Parens;
-   --  Called after scanning an expression (N) that does not require an extra
-   --  level of parentheses around the entire expression.
+   --  Called after scanning an entire expression (N) that does not require an
+   --  extra level of parentheses.
+
+   procedure Check_Xtra_Parens_Precedence (N : Node_Id)
+     renames Style_Inst.Check_Xtra_Parens_Precedence;
+   --  Called after scanning a subexpression (N) that does not require an
+   --  extra level of parentheses according to operator precedence rules.
 
    function Mode_In_Check return Boolean
      renames Style_Inst.Mode_In_Check;
diff --git a/gcc/ada/styleg.adb b/gcc/ada/styleg.adb
index 01a650ab181..a7524ec0526 100644
--- a/gcc/ada/styleg.adb
+++ b/gcc/ada/styleg.adb
@@ -1119,12 +1119,9 @@ package body Styleg is
    -- Check_Xtra_Parens --
    -----------------------
 
-   procedure Check_Xtra_Parens (N : Node_Id; Enable : Boolean) is
+   procedure Check_Xtra_Parens (N : Node_Id) is
    begin
-      --  Do not emit messages about expressions that may require parentheses
-
       if Style_Check_Xtra_Parens
-        and then Enable
         and then
           Paren_Count (N) >
             (if Nkind (N) in N_Case_Expression
@@ -1140,6 +1137,28 @@ package body Styleg is
       end if;
    end Check_Xtra_Parens;
 
+   ----------------------------------
+   -- Check_Xtra_Parens_Precedence --
+   ----------------------------------
+
+   procedure Check_Xtra_Parens_Precedence (N : Node_Id) is
+   begin
+      if Style_Check_Xtra_Parens_Precedence
+        and then
+          Paren_Count (N) >
+            (if Nkind (N) in N_Case_Expression
+                           | N_Expression_With_Actions
+                           | N_If_Expression
+                           | N_Quantified_Expression
+                           | N_Raise_Expression
+             then 1
+             else 0)
+      then
+         Error_Msg -- CODEFIX
+           ("(style) redundant parentheses?z?", Errout.First_Sloc (N));
+      end if;
+   end Check_Xtra_Parens_Precedence;
+
    ----------------------------
    -- Determine_Token_Casing --
    ----------------------------
diff --git a/gcc/ada/styleg.ads b/gcc/ada/styleg.ads
index aa4f65e7d99..7a610a198d1 100644
--- a/gcc/ada/styleg.ads
+++ b/gcc/ada/styleg.ads
@@ -160,10 +160,13 @@ package Styleg is
    procedure Check_Vertical_Bar;
    --  Called after scanning a vertical bar to check spacing
 
-   procedure Check_Xtra_Parens (N : Node_Id; Enable : Boolean);
-   --  Called after scanning an expression (N) that does not require an extra
-   --  level of parentheses around the entire expression.
-   --  Enable is a temporary parameter before enabling these checks by default.
+   procedure Check_Xtra_Parens (N : Node_Id);
+   --  Called after scanning an entire expression (N) that does not require an
+   --  extra level of parentheses.
+
+   procedure Check_Xtra_Parens_Precedence (N : Node_Id);
+   --  Called after scanning a subexpression (N) that does not require an
+   --  extra level of parentheses according to operator precedence rules.
 
    function Mode_In_Check return Boolean;
    pragma Inline (Mode_In_Check);
diff --git a/gcc/ada/stylesw.adb b/gcc/ada/stylesw.adb
index 2edc9e846c2..1b2acfb2fd9 100644
--- a/gcc/ada/stylesw.adb
+++ b/gcc/ada/stylesw.adb
@@ -58,12 +58,8 @@ package body Stylesw is
                      "I" &  -- check mode IN
                      "S" &  -- check separate lines after THEN or ELSE
                      "u" &  -- check no unnecessary blank lines
-                     "x";   -- check extra parentheses around conditionals
-
-   --  Note: we intend GNAT_Style to also include the following, but we do
-   --  not yet have the whole tool suite clean with respect to this.
-
-   --                "B" &  -- check boolean operators
+                     "x" &  -- check extra parentheses around conditionals
+                     "z";   -- check parens not required by precedence rules.
 
    -------------------------------
    -- Reset_Style_Check_Options --
@@ -71,33 +67,34 @@ package body Stylesw is
 
    procedure Reset_Style_Check_Options is
    begin
-      Style_Check_Indentation           := 0;
-      Style_Check_Array_Attribute_Index := False;
-      Style_Check_Attribute_Casing      := False;
-      Style_Check_Blanks_At_End         := False;
-      Style_Check_Blank_Lines           := False;
-      Style_Check_Boolean_And_Or        := False;
-      Style_Check_Comments              := False;
-      Style_Check_DOS_Line_Terminator   := False;
-      Style_Check_Mixed_Case_Decls      := False;
-      Style_Check_End_Labels            := False;
-      Style_Check_Form_Feeds            := False;
-      Style_Check_Horizontal_Tabs       := False;
-      Style_Check_If_Then_Layout        := False;
-      Style_Check_Keyword_Casing        := False;
-      Style_Check_Layout                := False;
-      Style_Check_Max_Line_Length       := False;
-      Style_Check_Max_Nesting_Level     := False;
-      Style_Check_Missing_Overriding    := False;
-      Style_Check_Mode_In               := False;
-      Style_Check_Order_Subprograms     := False;
-      Style_Check_Pragma_Casing         := False;
-      Style_Check_References            := False;
-      Style_Check_Separate_Stmt_Lines   := False;
-      Style_Check_Specs                 := False;
-      Style_Check_Standard              := False;
-      Style_Check_Tokens                := False;
-      Style_Check_Xtra_Parens           := False;
+      Style_Check_Indentation            := 0;
+      Style_Check_Array_Attribute_Index  := False;
+      Style_Check_Attribute_Casing       := False;
+      Style_Check_Blanks_At_End          := False;
+      Style_Check_Blank_Lines            := False;
+      Style_Check_Boolean_And_Or         := False;
+      Style_Check_Comments               := False;
+      Style_Check_DOS_Line_Terminator    := False;
+      Style_Check_Mixed_Case_Decls       := False;
+      Style_Check_End_Labels             := False;
+      Style_Check_Form_Feeds             := False;
+      Style_Check_Horizontal_Tabs        := False;
+      Style_Check_If_Then_Layout         := False;
+      Style_Check_Keyword_Casing         := False;
+      Style_Check_Layout                 := False;
+      Style_Check_Max_Line_Length        := False;
+      Style_Check_Max_Nesting_Level      := False;
+      Style_Check_Missing_Overriding     := False;
+      Style_Check_Mode_In                := False;
+      Style_Check_Order_Subprograms      := False;
+      Style_Check_Pragma_Casing          := False;
+      Style_Check_References             := False;
+      Style_Check_Separate_Stmt_Lines    := False;
+      Style_Check_Specs                  := False;
+      Style_Check_Standard               := False;
+      Style_Check_Tokens                 := False;
+      Style_Check_Xtra_Parens            := False;
+      Style_Check_Xtra_Parens_Precedence := False;
    end Reset_Style_Check_Options;
 
    ---------------------
@@ -187,6 +184,7 @@ package body Stylesw is
       Add ('t', Style_Check_Tokens);
       Add ('u', Style_Check_Blank_Lines);
       Add ('x', Style_Check_Xtra_Parens);
+      Add ('z', Style_Check_Xtra_Parens_Precedence);
 
       if Style_Check_Max_Line_Length then
          P := P + 1;
@@ -426,44 +424,47 @@ package body Stylesw is
                     or else Options (Err_Col) not in '0' .. '9';
                end loop;
 
-               Style_Check_Max_Line_Length       := Style_Max_Line_Length /= 0;
+               Style_Check_Max_Line_Length := Style_Max_Line_Length /= 0;
 
             when 'n' =>
-               Style_Check_Standard              := True;
+               Style_Check_Standard               := True;
 
             when 'N' =>
                Reset_Style_Check_Options;
 
             when 'o' =>
-               Style_Check_Order_Subprograms     := True;
+               Style_Check_Order_Subprograms      := True;
 
             when 'O' =>
-               Style_Check_Missing_Overriding    := True;
+               Style_Check_Missing_Overriding     := True;
 
             when 'p' =>
-               Style_Check_Pragma_Casing         := True;
+               Style_Check_Pragma_Casing          := True;
 
             when 'r' =>
-               Style_Check_References            := True;
+               Style_Check_References             := True;
 
             when 's' =>
-               Style_Check_Specs                 := True;
+               Style_Check_Specs                  := True;
 
             when 'S' =>
-               Style_Check_Separate_Stmt_Lines   := True;
+               Style_Check_Separate_Stmt_Lines    := True;
 
             when 't' =>
-               Style_Check_Tokens                := True;
+               Style_Check_Tokens                 := True;
 
             when 'u' =>
-               Style_Check_Blank_Lines           := True;
+               Style_Check_Blank_Lines            := True;
 
             when 'x' =>
-               Style_Check_Xtra_Parens           := True;
+               Style_Check_Xtra_Parens            := True;
 
             when 'y' =>
                Set_Default_Style_Check_Options;
 
+            when 'z' =>
+               Style_Check_Xtra_Parens_Precedence := True;
+
             when ' ' =>
                null;
 
@@ -491,89 +492,92 @@ package body Stylesw is
                Style_Check_Indentation := 0;
 
             when 'a' =>
-               Style_Check_Attribute_Casing      := False;
+               Style_Check_Attribute_Casing       := False;
 
             when 'A' =>
-               Style_Check_Array_Attribute_Index := False;
+               Style_Check_Array_Attribute_Index  := False;
 
             when 'b' =>
-               Style_Check_Blanks_At_End         := False;
+               Style_Check_Blanks_At_End          := False;
 
             when 'B' =>
-               Style_Check_Boolean_And_Or        := False;
+               Style_Check_Boolean_And_Or         := False;
 
             when 'c' | 'C' =>
-               Style_Check_Comments              := False;
+               Style_Check_Comments               := False;
 
             when 'd' =>
-               Style_Check_DOS_Line_Terminator   := False;
+               Style_Check_DOS_Line_Terminator    := False;
 
             when 'D' =>
-               Style_Check_Mixed_Case_Decls      := False;
+               Style_Check_Mixed_Case_Decls       := False;
 
             when 'e' =>
-               Style_Check_End_Labels            := False;
+               Style_Check_End_Labels             := False;
 
             when 'f' =>
-               Style_Check_Form_Feeds            := False;
+               Style_Check_Form_Feeds             := False;
 
             when 'g' =>
                Reset_Style_Check_Options;
 
             when 'h' =>
-               Style_Check_Horizontal_Tabs       := False;
+               Style_Check_Horizontal_Tabs        := False;
 
             when 'i' =>
-               Style_Check_If_Then_Layout        := False;
+               Style_Check_If_Then_Layout         := False;
 
             when 'I' =>
-               Style_Check_Mode_In               := False;
+               Style_Check_Mode_In                := False;
 
             when 'k' =>
-               Style_Check_Keyword_Casing        := False;
+               Style_Check_Keyword_Casing         := False;
 
             when 'l' =>
-               Style_Check_Layout                := False;
+               Style_Check_Layout                 := False;
 
             when 'L' =>
                Style_Max_Nesting_Level := 0;
 
             when 'm' =>
-               Style_Check_Max_Line_Length       := False;
+               Style_Check_Max_Line_Length        := False;
 
             when 'M' =>
-               Style_Max_Line_Length             := 0;
-               Style_Check_Max_Line_Length       := False;
+               Style_Max_Line_Length              := 0;
+               Style_Check_Max_Line_Length        := False;
 
             when 'n' =>
-               Style_Check_Standard              := False;
+               Style_Check_Standard               := False;
 
             when 'o' =>
-               Style_Check_Order_Subprograms     := False;
+               Style_Check_Order_Subprograms      := False;
 
             when 'O' =>
-               Style_Check_Missing_Overriding    := False;
+               Style_Check_Missing_Overriding     := False;
 
             when 'p' =>
-               Style_Check_Pragma_Casing         := False;
+               Style_Check_Pragma_Casing          := False;
 
             when 'r' =>
-               Style_Check_References            := False;
+               Style_Check_References             := False;
 
             when 's' =>
-               Style_Check_Specs                 := False;
+               Style_Check_Specs                  := False;
 
             when 'S' =>
-               Style_Check_Separate_Stmt_Lines   := False;
+               Style_Check_Separate_Stmt_Lines    := False;
 
             when 't' =>
-               Style_Check_Tokens                := False;
+               Style_Check_Tokens                 := False;
 
             when 'u' =>
-               Style_Check_Blank_Lines           := False;
+               Style_Check_Blank_Lines            := False;
 
             when 'x' =>
-               Style_Check_Xtra_Parens           := False;
+               Style_Check_Xtra_Parens            := False;
+
+            when 'z' =>
+               Style_Check_Xtra_Parens_Precedence := False;
 
             when ' ' =>
                null;
diff --git a/gcc/ada/stylesw.ads b/gcc/ada/stylesw.ads
index 3f8cc7850c1..18428e1f315 100644
--- a/gcc/ada/stylesw.ads
+++ b/gcc/ada/stylesw.ads
@@ -279,6 +279,11 @@ package Stylesw is
    --  not allowed to enclose entire expressions in tests in parentheses
    --  (C style), e.g. if (x = y) then ... is not allowed.
 
+   Style_Check_Xtra_Parens_Precedence : Boolean := False;
+   --  This can be set True by using the -gnatyz switch. If true, then it is
+   --  not allowed to enclose subexpressions in parentheses when not required
+   --  by operator precedence rules, e.g. (X > 1) and (Y < 1).
+
    Style_Max_Line_Length : Nat := 0;
    --  Value used to check maximum line length. Gets reset as a result of
    --  use of -gnatym or -gnatyMnnn switches. This value is only read if
diff --git a/gcc/ada/usage.adb b/gcc/ada/usage.adb
index 9e2aa019573..58cfa786efa 100644
--- a/gcc/ada/usage.adb
+++ b/gcc/ada/usage.adb
@@ -683,6 +683,8 @@ begin
    Write_Line ("        u    check no unnecessary blank lines");
    Write_Line ("        x    check extra parentheses around conditionals");
    Write_Line ("        y    turn on default style checks");
+   Write_Line ("        z    check parentheses not required by operator " &
+               "precedence rules");
    Write_Line ("        -    subtract (turn off) subsequent checks");
    Write_Line ("        +    add (turn on) subsequent checks");
 
