Factor out the predicate code for loopsimplify form exit blocks into

a separate helper function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86159 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/LoopInfo.h

@@ -572,6 +572,10 @@ public:
   /// normal form.
   bool isLoopSimplifyForm() const;
 
+  /// hasDedicatedExits - Return true if no exit block for the loop
+  /// has a predecessor that is outside the loop.
+  bool hasDedicatedExits() const;
+
   /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 
   /// These are the blocks _outside of the current loop_ which are branched to.
   /// This assumes that loop is in canonical form.

lib/Analysis/LoopInfo.cpp

@@ -286,12 +286,14 @@ bool Loop::isLCSSAForm() const {
 /// the LoopSimplify form transforms loops to, which is sometimes called
 /// normal form.
 bool Loop::isLoopSimplifyForm() const {
-  // Normal-form loops have a preheader.
+  // Normal-form loops have a preheader, a single backedge, and all of their
-  if (!getLoopPreheader())
+  // exits have all their predecessors inside the loop.
-    return false;
+  return getLoopPreheader() && getLoopLatch() && hasDedicatedExits();
-  // Normal-form loops have a single backedge.
+}
-  if (!getLoopLatch())
+
-    return false;
+/// hasDedicatedExits - Return true if no exit block for the loop
+/// has a predecessor that is outside the loop.
+bool Loop::hasDedicatedExits() const {
   // Sort the blocks vector so that we can use binary search to do quick
   // lookups.
   SmallPtrSet<BasicBlock *, 16> LoopBBs(block_begin(), block_end());