Nick Lewycky pointed out that this code makes changes unconditionally.

[oota-llvm.git] / lib / Transforms / Utils / BasicBlockUtils.cpp

diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 736d26e75fb9da4e8df7725a54357649cd200eb8..e902688f2066004427dca50bfc9288d150c764ad 100644 (file)
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -16,7 +16,6 @@
 #include "llvm/Function.h"
 #include "llvm/Instructions.h"
 #include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
 #include "llvm/Constant.h"
 #include "llvm/Type.h"
 #include "llvm/Analysis/AliasAnalysis.h"
@@ -65,9 +64,6 @@ void llvm::DeleteDeadBlock(BasicBlock *BB) {
 /// when all entries to the PHI nodes in a block are guaranteed equal, such as
 /// when the block has exactly one predecessor.
 void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
-  if (!isa<PHINode>(BB->begin()))
-    return;
-  
   while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
     if (PN->getIncomingValue(0) != PN)
       PN->replaceAllUsesWith(PN->getIncomingValue(0));
@@ -82,7 +78,7 @@ void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
 /// is dead. Also recursively delete any operands that become dead as
 /// a result. This includes tracing the def-use list from the PHI to see if
 /// it is ultimately unused or if it reaches an unused cycle.
-void llvm::DeleteDeadPHIs(BasicBlock *BB) {
+bool llvm::DeleteDeadPHIs(BasicBlock *BB) {
   // Recursively deleting a PHI may cause multiple PHIs to be deleted
   // or RAUW'd undef, so use an array of WeakVH for the PHIs to delete.
   SmallVector<WeakVH, 8> PHIs;
@@ -90,17 +86,24 @@ void llvm::DeleteDeadPHIs(BasicBlock *BB) {
        PHINode *PN = dyn_cast<PHINode>(I); ++I)
     PHIs.push_back(PN);
 
+  bool Changed = false;
   for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
     if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
-      RecursivelyDeleteDeadPHINode(PN);
+      Changed |= RecursivelyDeleteDeadPHINode(PN);
+
+  return Changed;
 }
 
 /// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
 /// if possible.  The return value indicates success or failure.
-bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
+bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
   pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
-  // Can't merge the entry block.
-  if (pred_begin(BB) == pred_end(BB)) return false;
+  // Can't merge the entry block.  Don't merge away blocks who have their
+  // address taken: this is a bug if the predecessor block is the entry node
+  // (because we'd end up taking the address of the entry) and undesirable in
+  // any case.
+  if (pred_begin(BB) == pred_end(BB) ||
+      BB->hasAddressTaken()) return false;
   
   BasicBlock *PredBB = *PI++;
   for (; PI != PE; ++PI)  // Search all predecessors, see if they are all same
@@ -252,7 +255,7 @@ void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
       Value *RetVal = 0;
 
       // Create a value to return... if the function doesn't return null...
-      if (BB->getParent()->getReturnType() != Type::getVoidTy(TI->getContext()))
+      if (!BB->getParent()->getReturnType()->isVoidTy())
         RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
 
       // Create the return...
@@ -383,6 +386,12 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
   bool IsLoopEntry = !!L;
   bool SplitMakesNewLoopHeader = false;
   for (unsigned i = 0; i != NumPreds; ++i) {
+    // This is slightly more strict than necessary; the minimum requirement
+    // is that there be no more than one indirectbr branching to BB. And
+    // all BlockAddress uses would need to be updated.
+    assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
+           "Cannot split an edge from an IndirectBrInst");
+
     Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
 
     if (LI) {
@@ -425,14 +434,26 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
 
   if (L) {
     if (IsLoopEntry) {
-      if (Loop *PredLoop = LI->getLoopFor(Preds[0])) {
-        // Add the new block to the nearest enclosing loop (and not an
-        // adjacent loop).
-        while (PredLoop && !PredLoop->contains(BB))
-          PredLoop = PredLoop->getParentLoop();
-        if (PredLoop)
-          PredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
-      }
+      // Add the new block to the nearest enclosing loop (and not an
+      // adjacent loop). To find this, examine each of the predecessors and
+      // determine which loops enclose them, and select the most-nested loop
+      // which contains the loop containing the block being split.
+      Loop *InnermostPredLoop = 0;
+      for (unsigned i = 0; i != NumPreds; ++i)
+        if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
+          // Seek a loop which actually contains the block being split (to
+          // avoid adjacent loops).
+          while (PredLoop && !PredLoop->contains(BB))
+            PredLoop = PredLoop->getParentLoop();
+          // Select the most-nested of these loops which contains the block.
+          if (PredLoop &&
+              PredLoop->contains(BB) &&
+              (!InnermostPredLoop ||
+               InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
+            InnermostPredLoop = PredLoop;
+        }
+      if (InnermostPredLoop)
+        InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
     } else {
       L->addBasicBlockToLoop(NewBB, LI->getBase());
       if (SplitMakesNewLoopHeader)
@@ -655,16 +676,3 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
   return 0;
 }
 
-/// CopyPrecedingStopPoint - If I is immediately preceded by a StopPoint,
-/// make a copy of the stoppoint before InsertPos (presumably before copying
-/// or moving I).
-void llvm::CopyPrecedingStopPoint(Instruction *I, 
-                                  BasicBlock::iterator InsertPos) {
-  if (I != I->getParent()->begin()) {
-    BasicBlock::iterator BBI = I;  --BBI;
-    if (DbgStopPointInst *DSPI = dyn_cast<DbgStopPointInst>(BBI)) {
-      CallInst *newDSPI = DSPI->clone(I->getContext());
-      newDSPI->insertBefore(InsertPos);
-    }
-  }
-}