Revert r176154 in favor of a better approach.

Code generation makes some basic assumptions about the IR it's been given. In
particular, if there is only one 'invoke' in the function, then that invoke
won't be going away. However, with the advent of the `llvm.donothing' intrinsic,
those invokes may go away. If all of them go away, the landing pad no longer has
any users. This confuses the back-end, which asserts.

This happens with SjLj exceptions, because that's the model that modifies the IR
based on there being invokes, etc. in the function.

Remove any invokes of `llvm.donothing' during SjLj EH preparation. This will
give us a CFG that the back-end won't be confused about. If all of the invokes
in a function are removed, then the SjLj EH prepare pass won't insert the bogus
code the relies upon the invokes being there.
<rdar://problem/13228754&13316637>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176677 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 11 insertions, 9 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 9a0bd23..33d100e 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1872,13 +1872,6 @@ void SelectionDAGBuilder::visitInvoke(const InvokeInst &I) {
     visitInlineAsm(&I);
   else if (Fn && Fn->isIntrinsic()) {
     assert(Fn->getIntrinsicID() == Intrinsic::donothing);
-    // If donothing has a landingpad, we should clear CurrentCallSite.
-    if (LandingPad) {
-      MachineModuleInfo &MMI = DAG.getMachineFunction().getMMI();
-      unsigned CallSiteIndex = MMI.getCurrentCallSite();
-      if (CallSiteIndex)
-        MMI.setCurrentCallSite(0);
-    }
     // Ignore invokes to @llvm.donothing: jump directly to the next BB.
   } else
     LowerCallTo(&I, getValue(Callee), false, LandingPad);
diff --git a/lib/CodeGen/SjLjEHPrepare.cpp b/lib/CodeGen/SjLjEHPrepare.cpp
index b58bb85..3903743 100644
--- a/lib/CodeGen/SjLjEHPrepare.cpp
+++ b/lib/CodeGen/SjLjEHPrepare.cpp
@@ -379,13 +379,22 @@ void SjLjEHPrepare::lowerAcrossUnwindEdges(Function &F,
 /// the function context and marking the call sites with the appropriate
 /// values. These values are used by the DWARF EH emitter.
 bool SjLjEHPrepare::setupEntryBlockAndCallSites(Function &F) {
-  SmallVector<ReturnInst*,     16> Returns;
-  SmallVector<InvokeInst*,     16> Invokes;
+  SmallVector<ReturnInst*, 16> Returns;
+  SmallVector<InvokeInst*, 16> Invokes;
   SmallSetVector<LandingPadInst*, 16> LPads;
 
   // Look through the terminators of the basic blocks to find invokes.
   for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
     if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+      if (Function *Callee = II->getCalledFunction())
+        if (Callee->isIntrinsic() &&
+            Callee->getIntrinsicID() == Intrinsic::donothing) {
+          // Remove the NOP invoke.
+          BranchInst::Create(II->getNormalDest(), II);
+          II->eraseFromParent();
+          continue;
+        }
+
       Invokes.push_back(II);
       LPads.insert(II->getUnwindDest()->getLandingPadInst());
     } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {