From d739eb8b490b481c9b75a12274f08afd695c8041 Mon Sep 17 00:00:00 2001
From: Andrew Macleod <amacleod@gcc.gnu.org>
Date: Mon, 9 Apr 2018 15:05:06 +0000
Subject: Implement intersect_mask to perform an intersection of a range with a
 bitmask.

From-SVN: r259236
---
 gcc/range.c | 40 ++++++++++++++++++++++++++++++++++++++++
 gcc/range.h |  2 ++
 2 files changed, 42 insertions(+)

diff --git a/gcc/range.c b/gcc/range.c
index 9e7c86b3..186ecff 100644
--- a/gcc/range.c
+++ b/gcc/range.c
@@ -681,6 +681,46 @@ irange::union_ (const irange &r)
   return *this;
 }
 
+// Intersect this range with a bitmask MASK.
+// Based on the bits in the mask, each lower bound is rounded up and each
+// upper bounds is rounded down.
+void
+irange::intersect_mask (const wide_int& mask)
+{
+  signop sign = TYPE_SIGN (type);
+  unsigned pos = 0;
+  
+  // Remove zero from the current range.
+  //
+  // seems to be a bug., I can't specify:
+  //
+  //   irange nz (type, 0, 0, INVERSE);
+  irange nz (type, 0 ,0);
+  nz.invert ();
+
+  intersect (nz);
+
+  for (unsigned i = 0; i < nitems; i += 2)
+    {
+      wide_int ub = wi::round_down_for_mask (bounds[i + 1], mask);
+      // Have to check for ub > lb immediately due to signed values
+      // potentially wrapping.  skip if not a valid range.
+      if (wi::gt_p (bounds[i], ub, sign))
+        continue;
+      wide_int lb = wi::round_up_for_mask (bounds[i], mask);
+
+      // If this is not a valid range, skip it
+      if (wi::gt_p (lb, ub, sign))
+        continue;
+      bounds[pos++] = lb;
+      bounds[pos++] = ub ;
+    }
+  nitems = pos;
+
+  // 0 is always a possible result, even if it wasn't in the original range.
+  union_ (irange (type, 0 , 0));
+}
+
 // THIS = THIS ^ [X,Y].
 
 irange &
diff --git a/gcc/range.h b/gcc/range.h
index 762f949..125a803 100644
--- a/gcc/range.h
+++ b/gcc/range.h
@@ -142,6 +142,8 @@ class irange
 
   const_tree get_type () const { return type; }
 
+  void intersect_mask (const wide_int& mask);
+
   irange& operator= (const irange &r);
   irange& operator= (const_tree t);
 
-- 
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