Re-commit my previous SSAUpdater changes. The previous version naively tried

to determine where to place PHIs by iteratively comparing reaching definitions
at each block.  That was just plain wrong.  This version now computes the
dominator tree within the subset of the CFG where PHIs may need to be placed,
and then places the PHIs in the iterated dominance frontier of each definition.
The rest of the patch is mostly the same, with a few more performance
improvements added in.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101612 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 9 deletions

diff --git a/include/llvm/Transforms/Utils/SSAUpdater.h b/include/llvm/Transforms/Utils/SSAUpdater.h
index 927e156..5b77ed6 100644
--- a/include/llvm/Transforms/Utils/SSAUpdater.h
+++ b/include/llvm/Transforms/Utils/SSAUpdater.h
@@ -21,28 +21,31 @@ namespace llvm {
   class PHINode;
   template<typename T>
   class SmallVectorImpl;
+  class BumpPtrAllocator;
 
 /// SSAUpdater - This class updates SSA form for a set of values defined in
 /// multiple blocks.  This is used when code duplication or another unstructured
 /// transformation wants to rewrite a set of uses of one value with uses of a
 /// set of values.
 class SSAUpdater {
+public:
+  class BBInfo;
+  typedef SmallVectorImpl<BBInfo*> BlockListTy;
+
+private:
   /// AvailableVals - This keeps track of which value to use on a per-block
-  /// basis.  When we insert PHI nodes, we keep track of them here.  We use
-  /// TrackingVH's for the value of the map because we RAUW PHI nodes when we
-  /// eliminate them, and want the TrackingVH's to track this.
-  //typedef DenseMap<BasicBlock*, TrackingVH<Value> > AvailableValsTy;
+  /// basis.  When we insert PHI nodes, we keep track of them here.
+  //typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
   void *AV;
 
   /// PrototypeValue is an arbitrary representative value, which we derive names
   /// and a type for PHI nodes.
   Value *PrototypeValue;
 
-  /// IncomingPredInfo - We use this as scratch space when doing our recursive
-  /// walk.  This should only be used in GetValueInBlockInternal, normally it
-  /// should be empty.
-  //std::vector<std::pair<BasicBlock*, TrackingVH<Value> > > IncomingPredInfo;
-  void *IPI;
+  /// BBMap - The GetValueAtEndOfBlock method maintains this mapping from
+  /// basic blocks to BBInfo structures.
+  /// typedef DenseMap<BasicBlock*, BBInfo*> BBMapTy;
+  void *BM;
 
   /// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
   /// it creates to the vector.
@@ -99,6 +102,15 @@ public:
 
 private:
   Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
+  void BuildBlockList(BasicBlock *BB, BlockListTy *BlockList,
+                      BumpPtrAllocator *Allocator);
+  void FindDominators(BlockListTy *BlockList);
+  void FindPHIPlacement(BlockListTy *BlockList);
+  void FindAvailableVals(BlockListTy *BlockList);
+  void FindExistingPHI(BasicBlock *BB, BlockListTy *BlockList);
+  bool CheckIfPHIMatches(PHINode *PHI);
+  void RecordMatchingPHI(PHINode *PHI);
+
   void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
   SSAUpdater(const SSAUpdater&);     // DO NOT IMPLEMENT
 };