Add Loop contains utility methods for testing whether a loop

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

diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index f3c175469ac1a7b3f27db050376640facdc8faaf..2962e8497e8d9a9a3d9cab338c40fc84b5d92414 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"
@@ -94,10 +93,14 @@ void llvm::DeleteDeadPHIs(BasicBlock *BB) {
 
 /// 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
@@ -380,6 +383,12 @@ 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) {