Make instcombine O(N) instead of O(N^2) in code where the same simplifiable constant is used many times.
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 4468f13..2993629 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -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;
}
}