Check for terminating conditions before adding PHIs to the worklists.

This is more efficient than adding them to the worklist and then ignoring them.

llvm-svn: 100158

1 files changed, 29 insertions, 21 deletions

diff --git a/llvm/lib/Transforms/Utils/SSAUpdater.cpp b/llvm/lib/Transforms/Utils/SSAUpdater.cpp
index 769e798faec..292332e4f8a 100644
--- a/llvm/lib/Transforms/Utils/SSAUpdater.cpp
+++ b/llvm/lib/Transforms/Utils/SSAUpdater.cpp
@@ -471,22 +471,27 @@ void SSAUpdater::RecordMatchingPHI(PHINode *PHI) {
   SmallVector<PHINode*, 20> WorkList;
   WorkList.push_back(PHI);
 
+  // Record this PHI.
+  BasicBlock *BB = PHI->getParent();
+  AvailableVals[BB] = PHI;
+  (*BBMap)[BB]->AvailableVal = PHI;
+
   while (!WorkList.empty()) {
     PHI = WorkList.pop_back_val();
-    BasicBlock *BB = PHI->getParent();
-    BBInfo *Info = (*BBMap)[BB];
-    if (!Info || Info->AvailableVal)
-      return;
-
-    // Record the PHI.
-    AvailableVals[BB] = PHI;
-    Info->AvailableVal = PHI;
 
     // Iterate through the PHI's incoming values.
     for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
-      PHINode *IncomingVal = dyn_cast<PHINode>(PHI->getIncomingValue(i));
-      if (!IncomingVal) continue;
-      WorkList.push_back(IncomingVal);
+      PHINode *IncomingPHIVal = dyn_cast<PHINode>(PHI->getIncomingValue(i));
+      if (!IncomingPHIVal) continue;
+      BB = IncomingPHIVal->getParent();
+      BBInfo *Info = (*BBMap)[BB];
+      if (!Info || Info->AvailableVal)
+        continue;
+
+      // Record the PHI and add it to the worklist.
+      AvailableVals[BB] = IncomingPHIVal;
+      Info->AvailableVal = IncomingPHIVal;
+      WorkList.push_back(IncomingPHIVal);
     }
   }
 }
@@ -499,21 +504,24 @@ void SSAUpdater::ClearPHITags(PHINode *PHI) {
   SmallVector<PHINode*, 20> WorkList;
   WorkList.push_back(PHI);
 
+  // Clear the tag for this PHI.
+  (*BBMap)[PHI->getParent()]->PHITag = 0;
+
   while (!WorkList.empty()) {
     PHI = WorkList.pop_back_val();
-    BasicBlock *BB = PHI->getParent();
-    BBInfo *Info = (*BBMap)[BB];
-    if (!Info || Info->AvailableVal || !Info->PHITag)
-      continue;
-
-    // Clear the tag.
-    Info->PHITag = 0;
 
     // Iterate through the PHI's incoming values.
     for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
-      PHINode *IncomingVal = dyn_cast<PHINode>(PHI->getIncomingValue(i));
-      if (!IncomingVal) continue;
-      WorkList.push_back(IncomingVal);
+      PHINode *IncomingPHIVal = dyn_cast<PHINode>(PHI->getIncomingValue(i));
+      if (!IncomingPHIVal) continue;
+      BasicBlock *BB = IncomingPHIVal->getParent();
+      BBInfo *Info = (*BBMap)[BB];
+      if (!Info || Info->AvailableVal || !Info->PHITag)
+        continue;
+
+      // Clear the tag and add the PHI to the worklist.
+      Info->PHITag = 0;
+      WorkList.push_back(IncomingPHIVal);
     }
   }
 }