[llvm] r234827 - [RewriteStatepointsForGC] Delete dead code [NFC]

[Philip Reames]

Author: reames
Date: Mon Apr 13 19:41:34 2015
New Revision: 234827

URL: http://llvm.org/viewvc/llvm-project?rev=234827&view=rev
Log:
[RewriteStatepointsForGC] Delete dead code [NFC]

Before we had real liveness, we needed to track every value that base pointer
insertion code created because these now might be live.  We now just rerun 
the data flow liveness algorithm (which is actually faster!) and no longer 
need the associated code.


Modified:
    llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp?rev=234827&r1=234826&r2=234827&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp Mon Apr 13 19:41:34 2015
@@ -131,10 +131,6 @@ struct PartiallyConstructedSafepointReco
   /// Mapping from live pointers to a base-defining-value
   DenseMap<llvm::Value *, llvm::Value *> PointerToBase;
 
-  /// Any new values which were added to the IR during base pointer analysis
-  /// for this safepoint
-  DenseSet<llvm::Value *> NewInsertedDefs;
-
   /// The *new* gc.statepoint instruction itself.  This produces the token
   /// that normal path gc.relocates and the gc.result are tied to.
   Instruction *StatepointToken;
@@ -584,8 +580,7 @@ private:
 /// from.  For gc objects, this is simply itself.  On success, returns a value
 /// which is the base pointer.  (This is reliable and can be used for
 /// relocation.)  On failure, returns nullptr.
-static Value *findBasePointer(Value *I, DefiningValueMapTy &cache,
-                              DenseSet<llvm::Value *> &NewInsertedDefs) {
+static Value *findBasePointer(Value *I, DefiningValueMapTy &cache) {
   Value *def = findBaseOrBDV(I, cache);
 
   if (isKnownBaseResult(def)) {
@@ -735,7 +730,6 @@ static Value *findBasePointer(Value *I,
           std::distance(pred_begin(v->getParent()), pred_end(v->getParent()));
       assert(num_preds > 0 && "how did we reach here");
       PHINode *phi = PHINode::Create(v->getType(), num_preds, "base_phi", v);
-      NewInsertedDefs.insert(phi);
       // Add metadata marking this as a base value
       auto *const_1 = ConstantInt::get(
           Type::getInt32Ty(
@@ -752,7 +746,6 @@ static Value *findBasePointer(Value *I,
       UndefValue *undef = UndefValue::get(sel->getType());
       SelectInst *basesel = SelectInst::Create(sel->getCondition(), undef,
                                                undef, "base_select", sel);
-      NewInsertedDefs.insert(basesel);
       // Add metadata marking this as a base value
       auto *const_1 = ConstantInt::get(
           Type::getInt32Ty(
@@ -803,8 +796,6 @@ static Value *findBasePointer(Value *I,
             assert(states.count(base));
             base = states[base].getBase();
             assert(base != nullptr && "unknown PhiState!");
-            assert(NewInsertedDefs.count(base) &&
-                   "should have already added this in a prev. iteration!");
           }
 
           // In essense this assert states: the only way two
@@ -835,7 +826,6 @@ static Value *findBasePointer(Value *I,
         if (base->getType() != basephi->getType()) {
           base = new BitCastInst(base, basephi->getType(), "cast",
                                  InBB->getTerminator());
-          NewInsertedDefs.insert(base);
         }
         basephi->addIncoming(base, InBB);
       }
@@ -861,7 +851,6 @@ static Value *findBasePointer(Value *I,
         // The cast is needed since base traversal may strip away bitcasts
         if (base->getType() != basesel->getType()) {
           base = new BitCastInst(base, basesel->getType(), "cast", basesel);
-          NewInsertedDefs.insert(base);
         }
         basesel->setOperand(i, base);
       }
@@ -919,8 +908,7 @@ static Value *findBasePointer(Value *I,
 static void
 findBasePointers(const StatepointLiveSetTy &live,
                  DenseMap<llvm::Value *, llvm::Value *> &PointerToBase,
-                 DominatorTree *DT, DefiningValueMapTy &DVCache,
-                 DenseSet<llvm::Value *> &NewInsertedDefs) {
+                 DominatorTree *DT, DefiningValueMapTy &DVCache) {
   // For the naming of values inserted to be deterministic - which makes for
   // much cleaner and more stable tests - we need to assign an order to the
   // live values.  DenseSets do not provide a deterministic order across runs.
@@ -928,7 +916,7 @@ findBasePointers(const StatepointLiveSet
   Temp.insert(Temp.end(), live.begin(), live.end());
   std::sort(Temp.begin(), Temp.end(), order_by_name);
   for (Value *ptr : Temp) {
-    Value *base = findBasePointer(ptr, DVCache, NewInsertedDefs);
+    Value *base = findBasePointer(ptr, DVCache);
     assert(base && "failed to find base pointer");
     PointerToBase[ptr] = base;
     assert((!isa<Instruction>(base) || !isa<Instruction>(ptr) ||
@@ -952,9 +940,7 @@ static void findBasePointers(DominatorTr
                              const CallSite &CS,
                              PartiallyConstructedSafepointRecord &result) {
   DenseMap<llvm::Value *, llvm::Value *> PointerToBase;
-  DenseSet<llvm::Value *> NewInsertedDefs;
-  findBasePointers(result.liveset, PointerToBase, &DT, DVCache,
-                   NewInsertedDefs);
+  findBasePointers(result.liveset, PointerToBase, &DT, DVCache);
 
   if (PrintBasePointers) {
     // Note: Need to print these in a stable order since this is checked in
@@ -974,7 +960,6 @@ static void findBasePointers(DominatorTr
   }
 
   result.PointerToBase = PointerToBase;
-  result.NewInsertedDefs = NewInsertedDefs;
 }
 
 /// Given an updated version of the dataflow liveness results, update the
@@ -1808,13 +1793,6 @@ static bool insertParsePoints(Function &
   //   gep a + 1
   //   safepoint 2
   //   br loop
-  DenseSet<llvm::Value *> allInsertedDefs;
-  for (size_t i = 0; i < records.size(); i++) {
-    struct PartiallyConstructedSafepointRecord &info = records[i];
-    allInsertedDefs.insert(info.NewInsertedDefs.begin(),
-                           info.NewInsertedDefs.end());
-  }
-
   // We insert some dummy calls after each safepoint to definitely hold live
   // the base pointers which were identified for that safepoint.  We'll then
   // ask liveness for _every_ base inserted to see what is now live.  Then we