Use df_ext_iterator to capture the reachable set without allocating an extra set.

Also, move large sets and vectors out of instance variables and onto the stack,
and give them more reasonable sizes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53044 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/ADCE.cpp b/lib/Transforms/Scalar/ADCE.cpp
index f7035e576b3039dac4d1be16582662d555c6432b..c5561995deb64c7dcc6852afe9c070f751869acc 100644 (file)
--- a/lib/Transforms/Scalar/ADCE.cpp
+++ b/lib/Transforms/Scalar/ADCE.cpp
@@ -22,10 +22,11 @@
 #include "llvm/Support/CFG.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/InstIterator.h"
-#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+
 
 using namespace llvm;
 
@@ -36,12 +37,6 @@ namespace {
     static char ID; // Pass identification, replacement for typeid
     ADCE() : FunctionPass((intptr_t)&ID) {}
     
-    DenseSet<Instruction*> alive;
-    SmallVector<Instruction*, 1024> worklist;
-    
-    DenseSet<BasicBlock*> reachable;
-    SmallVector<BasicBlock*, 1024> unreachable;
-    
     virtual bool runOnFunction(Function& F);
     
     virtual void getAnalysisUsage(AnalysisUsage& AU) const {
@@ -55,15 +50,17 @@ char ADCE::ID = 0;
 static RegisterPass<ADCE> X("adce", "Aggressive Dead Code Elimination");
 
 bool ADCE::runOnFunction(Function& F) {
-  alive.clear();
-  worklist.clear();
-  reachable.clear();
-  unreachable.clear();
+  SmallPtrSet<Instruction*, 128> alive;
+  SmallVector<Instruction*, 128> worklist;
+  
+  SmallPtrSet<BasicBlock*, 64> reachable;
+  SmallVector<BasicBlock*, 16> unreachable;
   
   // First, collect the set of reachable blocks ...
-  for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
-       DE = df_end(&F.getEntryBlock()); DI != DE; ++DI)
-    reachable.insert(*DI);
+  for (df_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 64> >
+       DI = df_ext_begin(&F.getEntryBlock(), reachable),
+       DE = df_ext_end(&F.getEntryBlock(), reachable); DI != DE; ++DI)
+    ; // Deliberately empty, df_ext_iterator will fill in the set.
   
   // ... and then invert it into the list of unreachable ones.  These
   // blocks will be removed from the function.
@@ -73,7 +70,7 @@ bool ADCE::runOnFunction(Function& F) {
   
   // Prepare to remove blocks by removing the PHI node entries for those blocks
   // in their successors, and remove them from reference counting.
-  for (SmallVector<BasicBlock*, 1024>::iterator UI = unreachable.begin(),
+  for (SmallVector<BasicBlock*, 16>::iterator UI = unreachable.begin(),
        UE = unreachable.end(); UI != UE; ++UI) {
     BasicBlock* BB = *UI;
     for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
@@ -90,7 +87,7 @@ bool ADCE::runOnFunction(Function& F) {
   }
   
   // Finally, erase the unreachable blocks.
-  for (SmallVector<BasicBlock*, 1024>::iterator UI = unreachable.begin(),
+  for (SmallVector<BasicBlock*, 16>::iterator UI = unreachable.begin(),
        UE = unreachable.end(); UI != UE; ++UI)
     (*UI)->eraseFromParent();