tree-vrp.c (range_fits_type_p): Require the MSB of the double_int to be clear for sign changes.

gcc/
	* tree-vrp.c (range_fits_type_p): Require the MSB of the double_int
	to be clear for sign changes.

gcc/testsuite/
	* gcc.dg/torture/fp-int-convert-2.c: New test.

From-SVN: r194800

gcc/ChangeLog

+2013-01-02  Richard Sandiford  <rdsandiford@googlemail.com>
+
+	* tree-vrp.c (range_fits_type_p): Require the MSB of the double_int
+	to be clear for sign changes.
+
 2013-01-01  Jan Hubicka  <jh@suse.cz>
 
 	* ipa-inline-analysis.c: Fix formatting.

gcc/testsuite/ChangeLog

+2013-01-02  Richard Sandiford  <rdsandiford@googlemail.com>
+
+	* gcc.dg/torture/fp-int-convert-2.c: New test.
+
 2013-01-01  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	* gfortran.dg/newunit_3.f90: Add dg-do run.

gcc/testsuite/gcc.dg/torture/fp-int-convert-2.c

+/* { dg-do run } */
+/* { dg-require-effective-target int128 } */
+
+extern void abort (void);
+
+float __attribute__((noinline))
+f (__uint128_t x)
+{
+  return x + 1;
+}
+
+int
+main (void)
+{
+  if (f (0xffffffffu) == 0)
+    abort ();
+  return 0;
+}

gcc/tree-vrp.c

@@ -8766,9 +8766,11 @@ range_fits_type_p (value_range_t *vr, unsigned precision, bool unsigned_p)
       || TREE_CODE (vr->max) != INTEGER_CST)
     return false;
 
-  /* For precision-preserving sign-changes the MSB of the double-int
-     has to be clear.  */
-  if (src_precision == precision
+  /* For sign changes, the MSB of the double_int has to be clear.
+     An unsigned value with its MSB set cannot be represented by
+     a signed double_int, while a negative value cannot be represented
+     by an unsigned double_int.  */
+  if (TYPE_UNSIGNED (src_type) != unsigned_p
       && (TREE_INT_CST_HIGH (vr->min) | TREE_INT_CST_HIGH (vr->max)) < 0)
     return false;