re PR tree-optimization/45034 ("safe" conversion from unsigned to signed char gives broken code)

2010-07-29  Richard Guenther  <rguenther@suse.de>

	PR middle-end/45034
	* convert.c (convert_to_integer): Always use an unsigned
	type for narrowed negate and bitwise not.

	* gcc.c-torture/execute/pr45034.c: New testcase.

From-SVN: r162673

gcc/ChangeLog

+2010-07-29  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/45034
+	* convert.c (convert_to_integer): Always use an unsigned
+	type for narrowed negate and bitwise not.
+
 2010-07-29  Ira Rosen  <irar@il.ibm.com>
 
 	* tree-vect-loop.c (vect_create_epilog_for_reduction): Switch

gcc/convert.c

@@ -799,14 +799,7 @@ convert_to_integer (tree type, tree expr)
 	  /* This is not correct for ABS_EXPR,
 	     since we must test the sign before truncation.  */
 	  {
-	    tree typex;
-
-	    /* Don't do unsigned arithmetic where signed was wanted,
-	       or vice versa.  */
-	    if (TYPE_UNSIGNED (TREE_TYPE (expr)))
-	      typex = unsigned_type_for (type);
-	    else
-	      typex = signed_type_for (type);
+	    tree typex = unsigned_type_for (type);
 	    return convert (type,
 			    fold_build1 (ex_form, typex,
 					 convert (typex,

gcc/testsuite/ChangeLog

+2010-07-29  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/45034
+	* gcc.c-torture/execute/pr45034.c: New testcase.
+
 2010-07-28  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/45096

gcc/testsuite/gcc.c-torture/execute/pr45034.c

+extern void abort (void);
+static void fixnum_neg(signed char x, signed char *py, int *pv)
+{
+  unsigned char ux, uy;
+
+  ux = (unsigned char)x;
+  uy = -ux;
+  *py = (uy <= 127) ? (signed char)uy : (-(signed char)(255 - uy) - 1);
+  *pv = (x == -128) ? 1 : 0;
+}
+
+void __attribute__((noinline)) foo(int x, int y, int v)
+{
+  if (y < -128 || y > 127)
+    abort();
+}
+
+int test_neg(void)
+{
+  signed char x, y;
+  int v, err;
+
+  err = 0;
+  x = -128;
+  for (;;) {
+      fixnum_neg(x, &y, &v);
+      foo((int)x, (int)y, v);
+      if ((v && x != -128) || (!v && x == -128))
+	++err;
+      if (x == 127)
+	break;
+      ++x;
+  }
+  return err;
+}
+
+int main(void)
+{
+  if (sizeof (char) != 1)
+    return 0;
+  if (test_neg() != 0)
+    abort();
+  return 0;
+}
+