Add an assertion to catch indirectbr in SplitBlockPredecessors. This

makes several optimization passes abort in cases where they're currently
silently miscompiling code.

Remove the indirectbr assertion from SplitEdge. Indirectbr is only
a problem for critical edges, and SplitEdge defers to SplitCriticalEdge
to handle those, and SplitCriticalEdge has its own assertion for
indirectbr.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86147 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index c728c0bd5f1cdc29f85db3e3ab95429ce5833167..2974592fb5dca8087b052e2274f775e540827cee 100644 (file)
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -275,8 +275,6 @@ void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
 /// SplitEdge -  Split the edge connecting specified block. Pass P must 
 /// not be NULL. 
 BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
-  assert(!isa<IndirectBrInst>(BB->getTerminator()) &&
-         "Cannot split an edge from an IndirectBrInst");
   TerminatorInst *LatchTerm = BB->getTerminator();
   unsigned SuccNum = 0;
 #ifndef NDEBUG
@@ -386,6 +384,12 @@ 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) {