[llvm-commits] [llvm] r102009 - /llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp

[Bob Wilson]

Author: bwilson
Date: Wed Apr 21 13:39:03 2010
New Revision: 102009

URL: http://llvm.org/viewvc/llvm-project?rev=102009&view=rev
Log:
Fix a performance problem with the new SSAUpdater.  This showed up in the
GCCAS time for MultiSource/Benchmarks/ASCI_Purple/SMG2000.

Modified:
    llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp

Modified: llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp?rev=102009&r1=102008&r2=102009&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SSAUpdater.cpp Wed Apr 21 13:39:03 2010
@@ -529,9 +529,15 @@
          E = BlockList->rend(); I != E; ++I) {
     BBInfo *Info = *I;
 
-    // Check if this block contains a newly added PHI.
-    if (Info->DefBB != Info)
+    if (Info->DefBB != Info) {
+      // Record the available value at join nodes to speed up subsequent
+      // uses of this SSAUpdater for the same value.
+      if (Info->NumPreds > 1)
+        AvailableVals[Info->BB] = Info->DefBB->AvailableVal;
       continue;
+    }
+
+    // Check if this block contains a newly added PHI.
     PHINode *PHI = dyn_cast<PHINode>(Info->AvailableVal);
     if (!PHI || PHI->getNumIncomingValues() == Info->NumPreds)
       continue;