utils.c (max_size): Add special code to deal with the subtraction of a "negative...

	* gcc-interface/utils.c (max_size) <tcc_binary>: Add special code to
	deal with the subtraction of a "negative" value in an unsigned type.

From-SVN: r223837

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index 8ebf666b6ec7957d1211c934a8760a72fcbe7836..61ec1df1807dc91ab32c6af225c62697f6fd7273 100644 (file)
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-28  Eric Botcazou  <ebotcazou@adacore.com>
+
+       * gcc-interface/utils.c (max_size) <tcc_binary>: Add special code to
+       deal with the subtraction of a "negative" value in an unsigned type.
+
 2015-05-28  Eric Botcazou  <ebotcazou@adacore.com>
 
        * gcc-interface/decl.c (gnat_to_gnu_entity) <E_Subprogram_Type>: Do

diff --git a/gcc/ada/gcc-interface/utils.c b/gcc/ada/gcc-interface/utils.c
index 7615d2d727d8b32847d062264536e569608f12da..0871c3cbe3b48c6c3f4d81ffdd69517f8e10dc47 100644 (file)
--- a/gcc/ada/gcc-interface/utils.c
+++ b/gcc/ada/gcc-interface/utils.c
@@ -3443,9 +3443,23 @@ max_size (tree exp, bool max_p)
        if ((code == MINUS_EXPR || code == PLUS_EXPR)
            && TREE_CODE (lhs) == INTEGER_CST
            && TREE_OVERFLOW (lhs)
-           && !TREE_CONSTANT (rhs))
+           && TREE_CODE (rhs) != INTEGER_CST)
          return lhs;
 
+       /* If we are going to subtract a "negative" value in an unsigned type,
+          do the operation as an addition of the negated value, in order to
+          avoid creating a spurious overflow below.  */
+       if (code == MINUS_EXPR
+           && TYPE_UNSIGNED (type)
+           && TREE_CODE (rhs) == INTEGER_CST
+           && !TREE_OVERFLOW (rhs)
+           && tree_int_cst_sign_bit (rhs) != 0)
+         {
+           rhs = fold_build1 (NEGATE_EXPR, type, rhs);
+           code = PLUS_EXPR;
+         }
+
+       /* We need to detect overflows so we call size_binop here.  */
        return size_binop (code, lhs, rhs);
       }
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 282a3bebf0c828ce2c32a43c40f79c652eaddfa5..f9864884d4f436552dc8fd15c1476bcb1a67501b 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2015-05-28  Eric Botcazou  <ebotcazou@adacore.com>
+
+       * gnat.dg/discr43.adb: New test.
+
 2015-05-28  Eric Botcazou  <ebotcazou@adacore.com>
 
        * gnat.dg/varsize_temp.adb: Rename into...

diff --git a/gcc/testsuite/gnat.dg/discr43.adb b/gcc/testsuite/gnat.dg/discr43.adb
new file mode 100644 (file)
index 0000000..e0d4390
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/discr43.adb
@@ -0,0 +1,16 @@
+-- { dg-do compile }
+
+with Text_IO; use Text_IO;
+
+procedure Discr43 is
+
+  type Arr is array (Short_Integer range <>) of Boolean;
+
+  type Rec (LB : Short_Integer; UB : Short_Integer) is record
+    A : Arr (LB .. UB);
+  end record;
+
+begin
+  Put_Line ("Arr'Max_Size =" & Arr'Max_Size_In_Storage_Elements'Img);
+  Put_Line ("Rec'Max_Size =" & Rec'Max_Size_In_Storage_Elements'Img);
+end;