[SROA] Fix the loop exit placement to be prior to indexing the splits

[oota-llvm.git] / lib / Transforms / Scalar / TailRecursionElimination.cpp

diff --git a/lib/Transforms/Scalar/TailRecursionElimination.cpp b/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 8f6855e6a3029c1e20d8403b87d533acc77eb9ff..f3c3e3054b60a8d09ce21bd8f8b0439e3a1786a0 100644 (file)
--- a/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -179,7 +179,7 @@ struct AllocaDerivedValueTracker {
 
     auto AddUsesToWorklist = [&](Value *V) {
       for (auto &U : V->uses()) {
-        if (!Visited.insert(&U))
+        if (!Visited.insert(&U).second)
           continue;
         Worklist.push_back(&U);
       }
@@ -253,7 +253,12 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
     return false;
   AllCallsAreTailCalls = true;
 
+  // The local stack holds all alloca instructions and all byval arguments.
   AllocaDerivedValueTracker Tracker;
+  for (Argument &Arg : F.args()) {
+    if (Arg.hasByValAttr())
+      Tracker.walk(&Arg);
+  }
   for (auto &BB : F) {
     for (auto &I : BB)
       if (AllocaInst *AI = dyn_cast<AllocaInst>(&I))
@@ -309,8 +314,9 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
         for (auto &Arg : CI->arg_operands()) {
           if (isa<Constant>(Arg.getUser()))
             continue;
-          if (isa<Argument>(Arg.getUser()))
-            continue;
+          if (Argument *A = dyn_cast<Argument>(Arg.getUser()))
+            if (!A->hasByValAttr())
+              continue;
           SafeToTail = false;
           break;
         }
@@ -398,18 +404,28 @@ bool TailCallElim::runTRE(Function &F) {
   // alloca' is changed from being a static alloca to being a dynamic alloca.
   // Until this is resolved, disable this transformation if that would ever
   // happen.  This bug is PR962.
+  SmallVector<BasicBlock*, 8> BBToErase;
   for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
     if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator())) {
       bool Change = ProcessReturningBlock(Ret, OldEntry, TailCallsAreMarkedTail,
                                           ArgumentPHIs, !CanTRETailMarkedCall);
-      if (!Change && BB->getFirstNonPHIOrDbg() == Ret)
+      if (!Change && BB->getFirstNonPHIOrDbg() == Ret) {
         Change = FoldReturnAndProcessPred(BB, Ret, OldEntry,
                                           TailCallsAreMarkedTail, ArgumentPHIs,
                                           !CanTRETailMarkedCall);
+        // FoldReturnAndProcessPred may have emptied some BB. Remember to
+        // erase them.
+        if (Change && BB->empty())
+          BBToErase.push_back(BB);
+
+      }
       MadeChange |= Change;
     }
   }
 
+  for (auto BB: BBToErase)
+    BB->eraseFromParent();
+
   // If we eliminated any tail recursions, it's possible that we inserted some
   // silly PHI nodes which just merge an initial value (the incoming operand)
   // with themselves.  Check to see if we did and clean up our mess if so.  This
@@ -817,8 +833,20 @@ bool TailCallElim::FoldReturnAndProcessPred(BasicBlock *BB,
     if (CallInst *CI = FindTRECandidate(BI, CannotTailCallElimCallsMarkedTail)){
       DEBUG(dbgs() << "FOLDING: " << *BB
             << "INTO UNCOND BRANCH PRED: " << *Pred);
-      EliminateRecursiveTailCall(CI, FoldReturnIntoUncondBranch(Ret, BB, Pred),
-                                 OldEntry, TailCallsAreMarkedTail, ArgumentPHIs,
+      ReturnInst *RI = FoldReturnIntoUncondBranch(Ret, BB, Pred);
+
+      // Cleanup: if all predecessors of BB have been eliminated by
+      // FoldReturnIntoUncondBranch, we would like to delete it, but we
+      // can not just nuke it as it is being used as an iterator by our caller.
+      // Just empty it, and the caller will erase it when it is safe to do so.
+      // It is important to empty it, because the ret instruction in there is
+      // still using a value which EliminateRecursiveTailCall will attempt
+      // to remove.
+      if (!BB->hasAddressTaken() && pred_begin(BB) == pred_end(BB))
+        BB->getInstList().clear();
+
+      EliminateRecursiveTailCall(CI, RI, OldEntry, TailCallsAreMarkedTail,
+                                 ArgumentPHIs,
                                  CannotTailCallElimCallsMarkedTail);
       ++NumRetDuped;
       Change = true;