Factor the ReachesChainWithoutSideEffects out of dag combiner into

a public SDOperand::reachesChainWithoutSideEffects method.  No 
functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46050 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 28 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 0bb11fa330..09e0c3e000 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4122,33 +4122,6 @@ SDOperand DAGCombiner::visitLOAD(SDNode *N) {
   return SDOperand();
 }
 
-/// ReachesChainWithoutSideEffects - Do a little local search to see if Src can
-/// reach Dest without any side effects like a store, or call.  Non-volatile
-/// loads are ok though.
-static bool ReachesChainWithoutSideEffects(SDOperand Src, SDOperand Dest,
-                                           unsigned Depth = 0) {
-  if (Src == Dest) return true;
-  
-  // Don't search too deeply, we just want to be able to see through
-  // TokenFactor's etc.
-  if (Depth == 2) return false;
-  
-  // If this is a token factor, all inputs to the TF happen in parallel.  If any
-  // of the operands of the TF reach dest, then we can do the xform.
-  if (Src.getOpcode() == ISD::TokenFactor) {
-    for (unsigned i = 0, e = Src.getNumOperands(); i != e; ++i)
-      if (ReachesChainWithoutSideEffects(Src.getOperand(i), Dest, Depth+1))
-        return true;
-    return false;
-  }
-  
-  // Loads don't have side effects, look through them.
-  if (LoadSDNode *Ld = dyn_cast<LoadSDNode>(Src)) {
-    if (!Ld->isVolatile())
-      return ReachesChainWithoutSideEffects(Ld->getChain(), Dest, Depth+1);
-  }
-  return false;
-}
 
 SDOperand DAGCombiner::visitSTORE(SDNode *N) {
   StoreSDNode *ST  = cast<StoreSDNode>(N);
@@ -4283,7 +4256,7 @@ SDOperand DAGCombiner::visitSTORE(SDNode *N) {
         !ST->isVolatile() &&
         // There can't be any side effects between the load and store, such as
         // a call or store.
-        ReachesChainWithoutSideEffects(Chain, SDOperand(Ld, 1))) {
+        Chain.reachesChainWithoutSideEffects(SDOperand(Ld, 1))) {
       // The store is dead, remove it.
       return Chain;
     }