[RTL ifcvt] PR rtl-optimization/66940: Avoid signed overflow in noce_get_alt_condition

	PR rtl-optimization/66940
	* ifcvt.c (noce_get_alt_condition): Check that incrementing or
	decrementing desired_val will not overflow before performing these
	operations.

	* gcc.c-torture/execute/pr66940.c: New test.

From-SVN: r236728

gcc/ChangeLog

+2016-05-25  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/66940
+	* ifcvt.c (noce_get_alt_condition): Check that incrementing or
+	decrementing desired_val will not overflow before performing these
+	operations.
+
 2016-05-25  Ilya Verbin  <ilya.verbin@intel.com>
 
 	* config/i386/i386-builtin-types.def: Add V16SI_FTYPE_V16SF,

gcc/ifcvt.c

@@ -2364,28 +2364,32 @@ noce_get_alt_condition (struct noce_if_info *if_info, rtx target,
 	  switch (code)
 	    {
 	    case LT:
-	      if (actual_val == desired_val + 1)
+	      if (desired_val != HOST_WIDE_INT_MAX
+		  && actual_val == desired_val + 1)
 		{
 		  code = LE;
 		  op_b = GEN_INT (desired_val);
 		}
 	      break;
 	    case LE:
-	      if (actual_val == desired_val - 1)
+	      if (desired_val != HOST_WIDE_INT_MIN
+		  && actual_val == desired_val - 1)
 		{
 		  code = LT;
 		  op_b = GEN_INT (desired_val);
 		}
 	      break;
 	    case GT:
-	      if (actual_val == desired_val - 1)
+	      if (desired_val != HOST_WIDE_INT_MIN
+		  && actual_val == desired_val - 1)
 		{
 		  code = GE;
 		  op_b = GEN_INT (desired_val);
 		}
 	      break;
 	    case GE:
-	      if (actual_val == desired_val + 1)
+	      if (desired_val != HOST_WIDE_INT_MAX
+		  && actual_val == desired_val + 1)
 		{
 		  code = GT;
 		  op_b = GEN_INT (desired_val);

gcc/testsuite/ChangeLog

+2016-05-25  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/66940
+	* gcc.c-torture/execute/pr66940.c: New test.
+
 2016-05-25  Ilya Verbin  <ilya.verbin@intel.com>
 
 	* gcc.target/i386/avx512f-ceil-vec-1.c: New test.

gcc/testsuite/gcc.c-torture/execute/pr66940.c

+long long __attribute__ ((noinline, noclone))
+foo (long long ival)
+{
+ if (ival <= 0)
+    return -0x7fffffffffffffffL - 1;
+
+ return 0x7fffffffffffffffL;
+}
+
+int
+main (void)
+{
+  if (foo (-1) != (-0x7fffffffffffffffL - 1))
+    __builtin_abort ();
+
+  if (foo (1) != 0x7fffffffffffffffL)
+    __builtin_abort ();
+
+  return 0;
+}