[PATCH] Fix VRP MULT_EXPR handling (PR tree-optimization/54471)

[Jakub Jelinek]

Hi!

If a type has 2 * HWI precision, sizem1 is maximum double_int (all ones)
and thus size = sizem1 + double_int_one overflows into 0.  If either min0
or min1 is also zero, we might wrongly canonicalize the range into a signed
one.  Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
ok for trunk?

2012-11-21  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/54471
        * tree-vrp.c (extract_range_from_binary_expr_1): For MULT_EXPR,
        don't canonicalize range if min2 is zero.

        * gcc.dg/tree-ssa/vrp86.c: New test.
        * gcc.c-torture/execute/pr54471.c: New test.

--- gcc/tree-vrp.c.jj   2012-11-21 16:00:05.000085079 +0100
+++ gcc/tree-vrp.c      2012-11-21 18:24:58.385290035 +0100
@@ -2653,7 +2653,7 @@ extract_range_from_binary_expr_1 (value_
          if (TYPE_UNSIGNED (expr_type))
            {
              double_int min2 = size - min0;
-             if (min2.cmp (max0, true) < 0)
+             if (!min2.is_zero () && min2.cmp (max0, true) < 0)
                {
                  min0 = -min2;
                  max0 -= size;
@@ -2661,7 +2661,7 @@ extract_range_from_binary_expr_1 (value_
                }
 
              min2 = size - min1;
-             if (min2.cmp (max1, true) < 0)
+             if (!min2.is_zero () && min2.cmp (max1, true) < 0)
                {
                  min1 = -min2;
                  max1 -= size;
--- gcc/testsuite/gcc.dg/tree-ssa/vrp86.c.jj    2012-11-21 18:27:53.389280736 
+0100
+++ gcc/testsuite/gcc.dg/tree-ssa/vrp86.c       2012-11-21 18:27:47.000000000 
+0100
@@ -0,0 +1,28 @@
+/* PR tree-optimization/54471 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp1" } */
+
+#ifdef __SIZEOF_INT128__
+#define T __int128
+#else
+#define T long long
+#endif
+
+void fn1call (void);
+void fn2call (void);
+
+void
+foo (unsigned T x)
+{
+  if (x > (unsigned T) -3)
+    return;
+  unsigned T y = 2 * x;
+  if (y == 42)
+    fn1call ();
+  else
+    fn2call ();
+}
+
+/* { dg-final { scan-tree-dump "fn1call" "vrp1"} } */
+/* { dg-final { scan-tree-dump "fn2call" "vrp1"} } */
+/* { dg-final { cleanup-tree-dump "vrp1" } } */
--- gcc/testsuite/gcc.c-torture/execute/pr54471.c.jj    2012-11-21 
18:24:58.386289954 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr54471.c       2012-11-21 
18:24:58.386289954 +0100
@@ -0,0 +1,36 @@
+/* PR tree-optimization/54471 */
+
+#ifdef __SIZEOF_INT128__
+#define T __int128
+#else
+#define T long long
+#endif
+
+extern void abort (void);
+
+__attribute__ ((noinline))
+unsigned T
+foo (T ixi, unsigned ctr)
+{
+  unsigned T irslt = 1;
+  T ix = ixi;
+
+  for (; ctr; ctr--)
+    {
+      irslt *= ix;
+      ix *= ix;
+    }
+
+  if (irslt != 14348907)
+    abort ();
+  return irslt;
+}
+
+int
+main ()
+{
+  unsigned T res;
+
+  res = foo (3, 4);
+  return 0;
+}

        Jakub