[CanonicalizeOSSABoundary] Used ::computeBoundary.

Previously, CanonicalizeOSSALifetime had its own copy of a variation of
the code for computing the liveness boundary that PrunedLiveness has.
Here, it is switched over to using PrunedLiveness' version.

In order to do that without complicating the interface for PrunedLivness
by adding a visitor, the extra bookkeeping that was being done for
destroy_values and debug_values is dropped.  Instead, after getting an
original boundary from PrunedLiveness::computeBoundary, the boundary is
extended out to preexisting destroys which are not separated from the
original boundary by "interesting" instructions.

Author: nate-chandler

include/swift/SILOptimizer/Utils/CanonicalOSSALifetime.h

@@ -134,18 +134,10 @@ class CanonicalOSSAConsumeInfo {
   /// Map blocks on the lifetime boundary to the last consuming instruction.
   llvm::SmallDenseMap<SILBasicBlock *, SILInstruction *, 4> finalBlockConsumes;
 
-  /// Record any debug_value instructions found after a final consume.
-  SmallVector<DebugValueInst *, 8> debugAfterConsume;
-
 public:
-  void clear() {
-    finalBlockConsumes.clear();
-    debugAfterConsume.clear();
-  }
+  void clear() { finalBlockConsumes.clear(); }
 
-  bool empty() {
-    return finalBlockConsumes.empty() && debugAfterConsume.empty();
-  }
+  bool empty() { return finalBlockConsumes.empty(); }
 
   bool hasUnclaimedConsumes() const { return !finalBlockConsumes.empty(); }
 
@@ -167,21 +159,6 @@ class CanonicalOSSAConsumeInfo {
     return false;
   }
 
-  /// Record a debug_value that is known to be outside pruned liveness. Assumes
-  /// that instructions are only visited once.
-  void recordDebugAfterConsume(DebugValueInst *dvi) {
-    debugAfterConsume.push_back(dvi);
-  }
-
-  void popDebugAfterConsume(DebugValueInst *dvi) {
-    if (!debugAfterConsume.empty() && debugAfterConsume.back() == dvi)
-      debugAfterConsume.pop_back();
-  }
-
-  ArrayRef<DebugValueInst *> getDebugInstsAfterConsume() const {
-    return debugAfterConsume;
-  }
-
   SWIFT_ASSERT_ONLY_DECL(void dump() const LLVM_ATTRIBUTE_USED);
 };
 
@@ -357,9 +334,7 @@ class CanonicalizeOSSALifetime {
   InstModCallbacks &getCallbacks() { return deleter.getCallbacks(); }
 
 protected:
-  void recordDebugValue(DebugValueInst *dvi) {
-    debugValues.insert(dvi);
-  }
+  void recordDebugValue(DebugValueInst *dvi) { debugValues.insert(dvi); }
 
   void recordConsumingUse(Operand *use) {
     consumingBlocks.insert(use->getUser()->getParent());
@@ -370,12 +345,9 @@ class CanonicalizeOSSALifetime {
 
   void extendLivenessThroughOverlappingAccess();
 
-  void findOrInsertDestroyInBlock(SILBasicBlock *bb);
-
-  void findOrInsertDestroys();
+  void findExtendedBoundary(PrunedLivenessBoundary &boundary);
 
-  void findOrInsertDestroyOnCFGEdge(SILBasicBlock *predBB,
-                                    SILBasicBlock *succBB);
+  void insertDestroysOnBoundary(PrunedLivenessBoundary &boundary);
 
   void rewriteCopies();
 };