From 2e60701b9d7ab5a0a8c68ed888665865554b6f4d Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 21 Mar 2008 21:33:23 +0000
Subject: [PATCH] make gvn marginally faster by reallocating the lastSeenLoad
 map for each basic block.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48660 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/GVN.cpp | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 077fa67e0bd..eb91b5a043d 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -1287,15 +1287,16 @@ bool GVN::iterateOnFunction(Function &F) {
   DominatorTree &DT = getAnalysis<DominatorTree>();   
   
   SmallVector<Instruction*, 4> toErase;
-  
+  DenseMap<Value*, LoadInst*> lastSeenLoad;
+
   // Top-down walk of the dominator tree
   for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()),
          E = df_end(DT.getRootNode()); DI != E; ++DI) {
     
     // Get the set to update for this block
     ValueNumberedSet& currAvail = availableOut[DI->getBlock()];     
-    DenseMap<Value*, LoadInst*> lastSeenLoad;
-    
+    lastSeenLoad.clear();
+
     BasicBlock* BB = DI->getBlock();
   
     // A block inherits AVAIL_OUT from its dominator