re PR rtl-optimization/41917 (Strange athrithmetic result with -O3)

	PR rtl-optimization/41917
	* rtlanal.c (num_sign_bit_copies1) <case UMOD>: If sign bit of second
	operand isn't known to be 0, return 1.

	* gcc.c-torture/execute/pr41917.c: New test.

From-SVN: r153874

gcc/ChangeLog

+2009-11-03  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/41917
+	* rtlanal.c (num_sign_bit_copies1) <case UMOD>: If sign bit of second
+	operand isn't known to be 0, return 1.
+
 2009-11-03  Richard Sandiford  <rdsandiford@googlemail.com>
 
 	* config/mips/mips.md: Fix typos.

gcc/rtlanal.c

@@ -4517,8 +4517,16 @@ num_sign_bit_copies1 (const_rtx x, enum machine_mode mode, const_rtx known_x,
 					   known_x, known_mode, known_ret);
 
     case UMOD:
-      /* The result must be <= the second operand.  */
-      return cached_num_sign_bit_copies (XEXP (x, 1), mode,
+      /* The result must be <= the second operand.  If the second operand
+	 has (or just might have) the high bit set, we know nothing about
+	 the number of sign bit copies.  */
+      if (bitwidth > HOST_BITS_PER_WIDE_INT)
+	return 1;
+      else if ((nonzero_bits (XEXP (x, 1), mode)
+		& ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0)
+	return 1;
+      else
+	return cached_num_sign_bit_copies (XEXP (x, 1), mode,
 					   known_x, known_mode, known_ret);
 
     case DIV:

gcc/testsuite/ChangeLog

+2009-11-03  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/41917
+	* gcc.c-torture/execute/pr41917.c: New test.
+
 2009-11-03  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc.target/i386/pr41900.c: Make test compile only.  Scan assembler

gcc/testsuite/gcc.c-torture/execute/pr41917.c

+/* PR rtl-optimization/41917 */
+
+extern void abort (void);
+unsigned int a = 1;
+
+int
+main (void)
+{
+  unsigned int b, c, d;
+
+  if (sizeof (int) != 4 || (int) 0xc7d24b5e > 0)
+    return 0;
+
+  c = 0xc7d24b5e;
+  d = a | -2;
+  b = (d == 0) ? c : (c % d);
+  if (b != c)
+    abort ();
+
+  return 0;
+}