[llvm-commits] [llvm] r131979 - /llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp

[Eli Friedman]

Author: efriedma
Date: Tue May 24 13:52:07 2011
New Revision: 131979

URL: http://llvm.org/viewvc/llvm-project?rev=131979&view=rev
Log:
Make instcombine O(N) instead of O(N^2) in code where the same simplifiable constant is used many times.
Part of rdar://9471075.


Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=131979&r1=131978&r2=131979&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Tue May 24 13:52:07 2011
@@ -1385,8 +1385,8 @@
   Worklist.push_back(BB);
 
   SmallVector<Instruction*, 128> InstrsForInstCombineWorklist;
-  SmallPtrSet<ConstantExpr*, 64> FoldedConstants;
-  
+  DenseMap<ConstantExpr*, Constant*> FoldedConstants;
+
   do {
     BB = Worklist.pop_back_val();
     
@@ -1421,14 +1421,15 @@
              i != e; ++i) {
           ConstantExpr *CE = dyn_cast<ConstantExpr>(i);
           if (CE == 0) continue;
-          
-          // If we already folded this constant, don't try again.
-          if (!FoldedConstants.insert(CE))
-            continue;
-          
-          Constant *NewC = ConstantFoldConstantExpression(CE, TD);
-          if (NewC && NewC != CE) {
-            *i = NewC;
+
+          Constant*& FoldRes = FoldedConstants[CE];
+          if (!FoldRes)
+            FoldRes = ConstantFoldConstantExpression(CE, TD);
+          if (!FoldRes)
+            FoldRes = CE;
+
+          if (FoldRes != CE) {
+            *i = FoldRes;
             MadeIRChange = true;
           }
         }