[PATCH] Check for overflow in tree-switch-conversion (PR middle-end/90478).

[Martin Liška]

Hi.

The patch is about handling of overflow in jump_table_cluster::can_be_handled.
I calculate 100 * range and compare it to range. If it's smaller, then
overflow happens.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

gcc/ChangeLog:

2019-05-15  Martin Liska  <mli...@suse.cz>

        PR middle-end/90478
        * tree-switch-conversion.c (jump_table_cluster::can_be_handled):
        Check for overflow.

gcc/testsuite/ChangeLog:

2019-05-15  Martin Liska  <mli...@suse.cz>

        PR middle-end/90478
        * gcc.dg/tree-ssa/pr90478-2.c: New test.
        * gcc.dg/tree-ssa/pr90478.c: New test.
---
 gcc/testsuite/gcc.dg/tree-ssa/pr90478-2.c | 17 +++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr90478.c   | 18 ++++++++++++++++++
 gcc/tree-switch-conversion.c              |  6 +++++-
 3 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr90478-2.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr90478.c



diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr90478-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr90478-2.c
new file mode 100644
index 00000000000..f0fc103a888
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr90478-2.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-Os --param jump-table-max-growth-ratio-for-size=2147483647" } */
+
+long
+foo (long x, long y)
+{
+  x = x & y;
+  switch (y)
+    {
+    case 63L: x >>= 0; break;
+    case 4032L: x >>= 6; break;
+    case 258048L: x >>= 12; break;
+    case 16515072L: x >>= 18; break;
+    default: __builtin_unreachable ();
+    }
+  return x;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr90478.c b/gcc/testsuite/gcc.dg/tree-ssa/pr90478.c
new file mode 100644
index 00000000000..f19808d2941
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr90478.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+
+typedef struct {
+  long a;
+} c;
+
+void e();
+
+void d() {
+  c *b;
+  switch (b->a)
+  case 8:
+  case 2:
+  case 2057594037927936:
+  case 0:
+  case 4611686018427387904:
+    e();
+}
diff --git a/gcc/tree-switch-conversion.c b/gcc/tree-switch-conversion.c
index bedeb2fd865..5f8ed46f496 100644
--- a/gcc/tree-switch-conversion.c
+++ b/gcc/tree-switch-conversion.c
@@ -1284,7 +1284,11 @@ jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
       comparison_count += sc->m_range_p ? 2 : 1;
     }
 
-  return 100 * range <= max_ratio * comparison_count;
+  unsigned HOST_WIDE_INT lhs = 100 * range;
+  if (lhs < range)
+    return false;
+
+  return lhs <= max_ratio * comparison_count;
 }
 
 /* Return true if cluster starting at START and ending at END (inclusive)