It's not possible to insert code immediately after an invoke in the

same basic block, and it's not safe to insert code in the successor
blocks if the edges are critical edges. Splitting those edges is
possible, but undesirable, especially on the unwind side. Instead,
make the bottom-up code motion to consider invokes to be part of
their successor blocks, rather than part of their parent blocks, so
that it doesn't push code past them and onto the edges. This fixes
PR12307.

llvm-svn: 153343

1 files changed, 42 insertions, 32 deletions

diff --git a/llvm/lib/Transforms/Scalar/ObjCARC.cpp b/llvm/lib/Transforms/Scalar/ObjCARC.cpp
index 8bebee47179..b5f91716f88 100644
--- a/llvm/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/llvm/lib/Transforms/Scalar/ObjCARC.cpp
@@ -1679,6 +1679,7 @@ namespace {
                             DenseMap<const BasicBlock *, BBState> &BBStates,
                             BBState &MyStates) const;
     bool VisitInstructionBottomUp(Instruction *Inst,
+                                  BasicBlock *BB,
                                   MapVector<Value *, RRInfo> &Retains,
                                   BBState &MyStates);
     bool VisitBottomUp(BasicBlock *BB,
@@ -2523,6 +2524,7 @@ ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
 
 bool
 ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
+                                     BasicBlock *BB,
                                      MapVector<Value *, RRInfo> &Retains,
                                      BBState &MyStates) {
   bool NestingDetected = false;
@@ -2642,14 +2644,24 @@ ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
     case S_MovableRelease:
       if (CanUse(Inst, Ptr, PA, Class)) {
         assert(S.RRI.ReverseInsertPts.empty());
-        S.RRI.ReverseInsertPts.insert(Inst);
+        // If this is an invoke instruction, we're scanning it as part of
+        // one of its successor blocks, since we can't insert code after it
+        // in its own block, and we don't want to split critical edges.
+        if (isa<InvokeInst>(Inst))
+          S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
+        else
+          S.RRI.ReverseInsertPts.insert(next(BasicBlock::iterator(Inst)));
         S.SetSeq(S_Use);
       } else if (Seq == S_Release &&
                  (Class == IC_User || Class == IC_CallOrUser)) {
         // Non-movable releases depend on any possible objc pointer use.
         S.SetSeq(S_Stop);
         assert(S.RRI.ReverseInsertPts.empty());
-        S.RRI.ReverseInsertPts.insert(Inst);
+        // As above; handle invoke specially.
+        if (isa<InvokeInst>(Inst))
+          S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
+        else
+          S.RRI.ReverseInsertPts.insert(next(BasicBlock::iterator(Inst)));
       }
       break;
     case S_Stop:
@@ -2713,7 +2725,23 @@ ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
   // Visit all the instructions, bottom-up.
   for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
     Instruction *Inst = llvm::prior(I);
-    NestingDetected |= VisitInstructionBottomUp(Inst, Retains, MyStates);
+
+    // Invoke instructions are visited as part of their successors (below).
+    if (isa<InvokeInst>(Inst))
+      continue;
+
+    NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates);
+  }
+
+  // If there's a predecessor with an invoke, visit the invoke as
+  // if it were part of this block, since we can't insert code after
+  // an invoke in its own block, and we don't want to split critical
+  // edges.
+  for (pred_iterator PI(BB), PE(BB, false); PI != PE; ++PI) {
+    BasicBlock *Pred = *PI;
+    TerminatorInst *PredTI = cast<TerminatorInst>(&Pred->back());
+    if (isa<InvokeInst>(PredTI))
+      NestingDetected |= VisitInstructionBottomUp(PredTI, BB, Retains, MyStates);
   }
 
   return NestingDetected;
@@ -3058,35 +3086,17 @@ void ObjCARCOpt::MoveCalls(Value *Arg,
   for (SmallPtrSet<Instruction *, 2>::const_iterator
        PI = RetainsToMove.ReverseInsertPts.begin(),
        PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
-    Instruction *LastUse = *PI;
-    Instruction *InsertPts[] = { 0, 0, 0 };
-    if (InvokeInst *II = dyn_cast<InvokeInst>(LastUse)) {
-      // We can't insert code immediately after an invoke instruction, so
-      // insert code at the beginning of both successor blocks instead.
-      // The invoke's return value isn't available in the unwind block,
-      // but our releases will never depend on it, because they must be
-      // paired with retains from before the invoke.
-      InsertPts[0] = II->getNormalDest()->getFirstInsertionPt();
-      if (!II->getMetadata(NoObjCARCExceptionsMDKind))
-        InsertPts[1] = II->getUnwindDest()->getFirstInsertionPt();
-    } else {
-      // Insert code immediately after the last use.
-      InsertPts[0] = llvm::next(BasicBlock::iterator(LastUse));
-    }
-
-    for (Instruction **I = InsertPts; *I; ++I) {
-      Instruction *InsertPt = *I;
-      Value *MyArg = ArgTy == ParamTy ? Arg :
-                     new BitCastInst(Arg, ParamTy, "", InsertPt);
-      CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
-                                        "", InsertPt);
-      // Attach a clang.imprecise_release metadata tag, if appropriate.
-      if (MDNode *M = ReleasesToMove.ReleaseMetadata)
-        Call->setMetadata(ImpreciseReleaseMDKind, M);
-      Call->setDoesNotThrow();
-      if (ReleasesToMove.IsTailCallRelease)
-        Call->setTailCall();
-    }
+    Instruction *InsertPt = *PI;
+    Value *MyArg = ArgTy == ParamTy ? Arg :
+                   new BitCastInst(Arg, ParamTy, "", InsertPt);
+    CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
+                                      "", InsertPt);
+    // Attach a clang.imprecise_release metadata tag, if appropriate.
+    if (MDNode *M = ReleasesToMove.ReleaseMetadata)
+      Call->setMetadata(ImpreciseReleaseMDKind, M);
+    Call->setDoesNotThrow();
+    if (ReleasesToMove.IsTailCallRelease)
+      Call->setTailCall();
   }
 
   // Delete the original retain and release calls.