[gcc r13-593] [Ada] Rework optimization skipping pragma check in object declaration

[gcc r13-593] [Ada] Rework optimization skipping pragma check in object declaration

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:8e4f37024ada46dafe1f8fd8464f0be118c6b961

commit r13-593-g8e4f37024ada46dafe1f8fd8464f0be118c6b961
Author: Marc Poulhiès <poulhies@adacore.com>
Date:   Fri Mar 18 10:32:41 2022 +0100

    [Ada] Rework optimization skipping pragma check in object declaration
    
    When an object declaration is initialized with a type conversion:
    
     Var : Typ := Typ (Value);
    
    we skip the check for Typ's predicate as it is already checked
    during the type conversion.
    
    This is not correct when Var's subtype and the target subtype of the
    conversion do not statically match:
    
     Var : Typ := OtherTyp (Value);
    
    In such case, we can't skip the check of Typ's predicate.
    
    Fix minor typos in comment.
    
    gcc/ada/
    
            * sem_ch3.adb (Analyze_Object_Declaration): Skip predicate check
            for type conversion if object's subtype and expression's subtype
            statically match.
            * exp_prag.adb (Expand_Pragma_Check): Typo fix in comment.

Diff:
---
 gcc/ada/exp_prag.adb |  2 +-
 gcc/ada/sem_ch3.adb  | 10 +++++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/gcc/ada/exp_prag.adb b/gcc/ada/exp_prag.adb
index 86a3929466a..5f1308777e8 100644
--- a/gcc/ada/exp_prag.adb
+++ b/gcc/ada/exp_prag.adb
@@ -285,7 +285,7 @@ package body Exp_Prag is
       --  expression is not usually the best choice here, because it points to
       --  the location of the topmost tree node, which may be an operator in
       --  the middle of the source text of the expression. For example, it gets
-      --  located on the last AND keyword in a chain of boolean expressiond
+      --  located on the last AND keyword in a chain of boolean expressions
       --  AND'ed together. It is best to put the message on the first character
       --  of the condition, which is the effect of the First_Node call here.
       --  This source location is used to build the default exception message,
diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index dfade0f9193..34dac1df624 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -4572,11 +4572,15 @@ package body Sem_Ch3 is
             null;
 
          --  Do not generate a predicate check if the initialization expression
-         --  is a type conversion because the conversion has been subjected to
-         --  the same check. This is a small optimization which avoid redundant
+         --  is a type conversion whose target subtype statically matches the
+         --  object's subtype because the conversion has been subjected to the
+         --  same check. This is a small optimization which avoids redundant
          --  checks.
 
-         elsif Present (E) and then Nkind (E) = N_Type_Conversion then
+         elsif Present (E)
+           and then Nkind (E) in N_Type_Conversion
+           and then Subtypes_Statically_Match (Etype (Subtype_Mark (E)), T)
+         then
             null;
 
          else