allow constructing a auto_vec with a preallocation, and a possibly larger actual allocation size

This allows us to set the capacity of the vector when we construct it,
and still use a stack buffer when the size is small enough.

gcc/ChangeLog:

2017-05-13  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>

	* genrecog.c (int_set::int_set): Explicitly construct our
	auto_vec base class.
	* vec.h (auto_vec::auto_vec): New constructor.

From-SVN: r248019

1 files changed, 12 insertions, 0 deletions

diff --git a/gcc/vec.h b/gcc/vec.h
index fee4616..914f89c 100644
--- a/gcc/vec.h
+++ b/gcc/vec.h
@@ -1272,6 +1272,18 @@ public:
     this->m_vec = &m_auto;
   }
 
+  auto_vec (size_t s)
+  {
+    if (s > N)
+      {
+	this->create (s);
+	return;
+      }
+
+    m_auto.embedded_init (MAX (N, 2), 0, 1);
+    this->m_vec = &m_auto;
+  }
+
   ~auto_vec ()
   {
     this->release ();