Revert r80926. It causes loop unswitch assertion and slow down some JIT tests significantly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81101 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 57 deletions

diff --git a/lib/Transforms/Utils/BreakCriticalEdges.cpp b/lib/Transforms/Utils/BreakCriticalEdges.cpp
index f5a136661f..632aa2b723 100644
--- a/lib/Transforms/Utils/BreakCriticalEdges.cpp
+++ b/lib/Transforms/Utils/BreakCriticalEdges.cpp
@@ -122,9 +122,9 @@ bool llvm::isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
 /// false otherwise.  This ensures that all edges to that dest go to one block
 /// instead of each going to a different block.
 //
-BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
-                                    Pass *P, bool MergeIdenticalEdges) {
-  if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0;
+bool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P,
+                             bool MergeIdenticalEdges) {
+  if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return false;
   BasicBlock *TIBB = TI->getParent();
   BasicBlock *DestBB = TI->getSuccessor(SuccNum);
 
@@ -172,7 +172,7 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
   
 
   // If we don't have a pass object, we can't update anything...
-  if (P == 0) return NewBB;
+  if (P == 0) return true;
 
   // Now update analysis information.  Since the only predecessor of NewBB is
   // the TIBB, TIBB clearly dominates NewBB.  TIBB usually doesn't dominate
@@ -254,9 +254,9 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
   
   // Update LoopInfo if it is around.
   if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>()) {
-    if (Loop *TIL = LI->getLoopFor(TIBB)) {
-      // If one or the other blocks were not in a loop, the new block is not
-      // either, and thus LI doesn't need to be updated.
+    // If one or the other blocks were not in a loop, the new block is not
+    // either, and thus LI doesn't need to be updated.
+    if (Loop *TIL = LI->getLoopFor(TIBB))
       if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
         if (TIL == DestLoop) {
           // Both in the same loop, the NewBB joins loop.
@@ -278,55 +278,6 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
             P->addBasicBlockToLoop(NewBB, LI->getBase());
         }
       }
-      // If TIBB is in a loop and DestBB is outside of that loop, split the
-      // other exit blocks of the loop that also have predecessors outside
-      // the loop, to maintain a LoopSimplify guarantee.
-      if (!TIL->contains(DestBB) &&
-          P->mustPreserveAnalysisID(LoopSimplifyID)) {
-        // For each unique exit block...
-        SmallVector<BasicBlock *, 4> ExitBlocks;
-        TIL->getExitBlocks(ExitBlocks);
-        for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
-          // Collect all the preds that are inside the loop, and note
-          // whether there are any preds outside the loop.
-          SmallVector<BasicBlock *, 4> Preds;
-          bool AllPredsInLoop = false;
-          BasicBlock *Exit = ExitBlocks[i];
-          for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit);
-               I != E; ++I)
-            if (TIL->contains(*I))
-              Preds.push_back(*I);
-            else
-              AllPredsInLoop = true;
-          // If there are any preds not in the loop, we'll need to split
-          // the edges. The Preds.empty() check is needed because a block
-          // may appear multiple times in the list. We can't use
-          // getUniqueExitBlocks above because that depends on LoopSimplify
-          // form, which we're in the process of restoring!
-          if (Preds.empty() || !AllPredsInLoop) continue;
-          BasicBlock *NewBB = SplitBlockPredecessors(Exit,
-                                                     Preds.data(), Preds.size(),
-                                                     "split", P);
-          // Update LCSSA form. This is fairly simple in LoopSimplify form:
-          // just move the existing LCSSA-mandated PHI nodes from the old exit
-          // block to the new one.
-          if (P->mustPreserveAnalysisID(LCSSAID))
-            for (BasicBlock::iterator I = Exit->begin();
-                 PHINode *PN = dyn_cast<PHINode>(I); ++I)
-              PN->moveBefore(NewBB->getTerminator());
-        }
-      }
-      // LCSSA form was updated above for the case where LoopSimplify is
-      // available, which means that all predecessors of loop exit blocks
-      // are within the loop. Without LoopSimplify form, it would be
-      // necessary to insert a new phi.
-      assert((!P->mustPreserveAnalysisID(LCSSAID) ||
-              P->mustPreserveAnalysisID(LoopSimplifyID)) &&
-             "SplitCriticalEdge doesn't know how to update LCCSA form "
-             "without LoopSimplify!");
-    }
-
   }
-
-  return NewBB;
+  return true;
 }