Make instcombine O(N) instead of O(N^2) in code where the same simplifiable constant...

Part of rdar://9471075.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131979 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 4468f13f631fd0e33ef0b4a8931e58ecab265ba7..2993629e90ef0d3a70df321be850db488381c855 100644 (file)
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1385,8 +1385,8 @@ static bool AddReachableCodeToWorklist(BasicBlock *BB,
   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 @@ static bool AddReachableCodeToWorklist(BasicBlock *BB,
              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;
           }
         }