X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FUtils%2FBreakCriticalEdges.cpp;h=0c4974db10ac4c325d94ceb981ace69ec4e5d53a;hb=cb2610ea037a17115ef3a01a6bdaab4e3cfdca27;hp=205ca2d46268aecaaaf59229e032f4ea0332bd62;hpb=eb0456c8fd60e6c2ef844d8696baa39d5d55f082;p=oota-llvm.git

diff --git a/lib/Transforms/Utils/BreakCriticalEdges.cpp b/lib/Transforms/Utils/BreakCriticalEdges.cpp
index 205ca2d4626..0c4974db10a 100644
--- a/lib/Transforms/Utils/BreakCriticalEdges.cpp
+++ b/lib/Transforms/Utils/BreakCriticalEdges.cpp
@@ -14,10 +14,10 @@
 #include "llvm/iTerminators.h"
 #include "llvm/iPHINode.h"
 #include "llvm/Support/CFG.h"
-#include "Support/StatisticReporter.h"
+#include "Support/Statistic.h"
 
 namespace {
-  Statistic<> NumBroken("break-crit-edges\t- Number of blocks inserted");
+  Statistic<> NumBroken("break-crit-edges", "Number of blocks inserted");
 
   struct BreakCriticalEdges : public FunctionPass {
     virtual bool runOnFunction(Function &F);
@@ -26,6 +26,7 @@ namespace {
       AU.addPreserved<DominatorSet>();
       AU.addPreserved<ImmediateDominators>();
       AU.addPreserved<DominatorTree>();
+      AU.addPreservedID(LoopPreheadersID);   // No preheaders deleted.
     }
   };
 
@@ -42,9 +43,9 @@ Pass *createBreakCriticalEdgesPass() { return new BreakCriticalEdges(); }
 // Critical edges are edges from a block with multiple successors to a block
 // with multiple predecessors.
 //
-static bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum) {
+bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum) {
   assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!");
-  assert (TI->getNumSuccessors() > 1);
+  if (TI->getNumSuccessors() == 1) return false;
 
   const BasicBlock *Dest = TI->getSuccessor(SuccNum);
   pred_const_iterator I = pred_begin(Dest), E = pred_end(Dest);
@@ -59,7 +60,7 @@ static bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum) {
 // will update DominatorSet, ImmediateDominator and DominatorTree information if
 // it is available, thus calling this pass will not invalidate either of them.
 //
-static void SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
+void SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
   assert(isCriticalEdge(TI, SuccNum) &&
          "Cannot break a critical edge, if it isn't a critical edge");
   BasicBlock *TIBB = TI->getParent();
@@ -87,36 +88,38 @@ static void SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
     PN->replaceUsesOfWith(TIBB, NewBB);
   }
 
-  // Now if we have a pass object, update analysis information.  Currently we
-  // update DominatorSet and DominatorTree information if it's available.
-  //
-  if (P) {
-    // Should we update DominatorSet information?
-    if (DominatorSet *DS = P->getAnalysisToUpdate<DominatorSet>()) {
-      // The blocks that dominate the new one are the blocks that dominate TIBB
-      // plus the new block itself.
-      DominatorSet::DomSetType DomSet = DS->getDominators(TIBB);
-      DomSet.insert(NewBB);  // A block always dominates itself.
-      DS->addBasicBlock(NewBB, DomSet);
-    }
+  // If we don't have a pass object, we can't update anything...
+  if (P == 0) return;
 
-    // Should we update ImmdediateDominator information?
-    if (ImmediateDominators *ID =
-        P->getAnalysisToUpdate<ImmediateDominators>()) {
-      // TIBB is the new immediate dominator for NewBB.  NewBB doesn't dominate
-      // anything.
-      ID->addNewBlock(NewBB, TIBB);
-    }
+  // Now update analysis information.  These are the analyses that we are
+  // currently capable of updating...
+  //
 
-    // Should we update DominatorTree information?
-    if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) {
-      DominatorTree::Node *TINode = DT->getNode(TIBB);
+  // Should we update DominatorSet information?
+  if (DominatorSet *DS = P->getAnalysisToUpdate<DominatorSet>()) {
+    // The blocks that dominate the new one are the blocks that dominate TIBB
+    // plus the new block itself.
+    DominatorSet::DomSetType DomSet = DS->getDominators(TIBB);
+    DomSet.insert(NewBB);  // A block always dominates itself.
+    DS->addBasicBlock(NewBB, DomSet);
+  }
 
-      // The new block is not the immediate dominator for any other nodes, but
-      // TINode is the immediate dominator for the new node.
-      //
+  // Should we update ImmdediateDominator information?
+  if (ImmediateDominators *ID = P->getAnalysisToUpdate<ImmediateDominators>()) {
+    // TIBB is the new immediate dominator for NewBB.  NewBB doesn't dominate
+    // anything.
+    ID->addNewBlock(NewBB, TIBB);
+  }
+  
+  // Should we update DominatorTree information?
+  if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) {
+    DominatorTree::Node *TINode = DT->getNode(TIBB);
+    
+    // The new block is not the immediate dominator for any other nodes, but
+    // TINode is the immediate dominator for the new node.
+    //
+    if (TINode)        // Don't break unreachable code!
       DT->createNewNode(NewBB, TINode);
-    }
   }
 }