LoopVectorize fix: LoopInfo must be valid when invoking utils like SCEVExpander.

In general, one should always complete CFG modifications first, update
CFG-based analyses, like Dominatores and LoopInfo, then generate
instruction sequences.

LoopVectorizer was creating a new loop, calling SCEVExpander to
generate checks, then updating LoopInfo. I just changed the order.

llvm-svn: 186241

1 files changed, 18 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index b35ed74497c..0d910d1559e 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1476,6 +1476,22 @@ InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
   BasicBlock *ScalarPH =
   MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph");
 
+  // Create and register the new vector loop.
+  Loop* Lp = new Loop();
+  Loop *ParentLoop = OrigLoop->getParentLoop();
+
+  // Insert the new loop into the loop nest and register the new basic blocks
+  // before calling any utilities such as SCEV that require valid LoopInfo.
+  if (ParentLoop) {
+    ParentLoop->addChildLoop(Lp);
+    ParentLoop->addBasicBlockToLoop(ScalarPH, LI->getBase());
+    ParentLoop->addBasicBlockToLoop(VectorPH, LI->getBase());
+    ParentLoop->addBasicBlockToLoop(MiddleBlock, LI->getBase());
+  } else {
+    LI->addTopLevelLoop(Lp);
+  }
+  Lp->addBasicBlockToLoop(VecBody, LI->getBase());
+
   // Use this IR builder to create the loop instructions (Phi, Br, Cmp)
   // inside the loop.
   Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
@@ -1530,6 +1546,8 @@ InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
     // Create a new block containing the memory check.
     BasicBlock *CheckBlock = BypassBlock->splitBasicBlock(MemRuntimeCheck,
                                                           "vector.memcheck");
+    if (ParentLoop)
+      ParentLoop->addBasicBlockToLoop(CheckBlock, LI->getBase());
     LoopBypassBlocks.push_back(CheckBlock);
 
     // Replace the branch into the memory check block with a conditional branch
@@ -1697,24 +1715,6 @@ InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) {
   // Get ready to start creating new instructions into the vectorized body.
   Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
 
-  // Create and register the new vector loop.
-  Loop* Lp = new Loop();
-  Loop *ParentLoop = OrigLoop->getParentLoop();
-
-  // Insert the new loop into the loop nest and register the new basic blocks.
-  if (ParentLoop) {
-    ParentLoop->addChildLoop(Lp);
-    for (unsigned I = 1, E = LoopBypassBlocks.size(); I != E; ++I)
-      ParentLoop->addBasicBlockToLoop(LoopBypassBlocks[I], LI->getBase());
-    ParentLoop->addBasicBlockToLoop(ScalarPH, LI->getBase());
-    ParentLoop->addBasicBlockToLoop(VectorPH, LI->getBase());
-    ParentLoop->addBasicBlockToLoop(MiddleBlock, LI->getBase());
-  } else {
-    LI->addTopLevelLoop(Lp);
-  }
-
-  Lp->addBasicBlockToLoop(VecBody, LI->getBase());
-
   // Save the state.
   LoopVectorPreHeader = VectorPH;
   LoopScalarPreHeader = ScalarPH;