Re-commit the safe parts of my 6/9 patch. Still working on fixing the unsafe parts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28748 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/LoopInfo.h

@@ -146,6 +146,9 @@ public:
   /// this returns null.
   ///
   Value *getTripCount() const;
+  
+  /// isLCSSAForm - Return true if the Loop is in LCSSA form
+  bool isLCSSAForm() const;
 
   //===--------------------------------------------------------------------===//
   // APIs for updating loop information after changing the CFG

lib/Analysis/LoopInfo.cpp

@@ -479,6 +479,22 @@ Value *Loop::getTripCount() const {
   return 0;
 }
 
+/// isLCSSAForm - Return true if the Loop is in LCSSA form
+bool Loop::isLCSSAForm() const {  
+  for (Loop::block_iterator BB = block_begin(), E = block_end();
+       BB != E; ++BB) {
+    for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end(); I != E; ++I)
+      for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
+           ++UI) {
+        BasicBlock *UserBB = cast<Instruction>(*UI)->getParent();
+        if (!isa<PHINode>(*UI) && !contains(UserBB)) {
+          return false;
+        }
+      }
+  }
+  
+  return true;
+}
 
 //===-------------------------------------------------------------------===//
 // APIs for updating loop information after changing the CFG

lib/Transforms/Utils/LCSSA.cpp

@@ -132,6 +132,8 @@ bool LCSSA::visitSubloop(Loop* L) {
     processInstruction(*I, exitBlocks);
   }
   
+  assert(L->isLCSSAForm());
+  
   return true;
 }