[WinEH] Emit int3 after noreturn calls on Win64

[oota-llvm.git] / lib / Target / X86 / X86ISelLowering.cpp

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 6fd04733e01dce21372cf0b17700320b3851250d..0ed196a4acb5f55b92fafcd47f83653e11c86b84 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2945,6 +2945,20 @@ static SDValue getMOVL(SelectionDAG &DAG, SDLoc dl, EVT VT, SDValue V1,
   return DAG.getVectorShuffle(VT, dl, V1, V2, &Mask[0]);
 }
 
+/// Check if the fall through instruction after a call site is unreachable.
+/// FIXME: This will fail if there are interesting non-code generating IR
+/// instructions between the call and the unreachable (lifetime.end). In
+/// practice, this should be rare because optimizations like to delete non-call
+/// code before unreachable.
+static bool isCallFollowedByUnreachable(ImmutableCallSite CS) {
+  const Instruction *NextInst;
+  if (auto *II = dyn_cast<InvokeInst>(CS.getInstruction()))
+    NextInst = II->getNormalDest()->getFirstNonPHIOrDbg();
+  else
+    NextInst = CS.getInstruction()->getNextNode();
+  return isa<UnreachableInst>(NextInst);
+}
+
 SDValue
 X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
                              SmallVectorImpl<SDValue> &InVals) const {
@@ -3450,6 +3464,15 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     InFlag = Chain.getValue(1);
   }
 
+  if (Subtarget->isTargetWin64() && CLI.CS) {
+    // Look for a call followed by unreachable. On Win64, we need to ensure that
+    // the call does not accidentally fall through to something that looks like
+    // an epilogue. We do this by inserting a DEBUGTRAP, which lowers to int3,
+    // which is what MSVC emits after noreturn calls.
+    if (isCallFollowedByUnreachable(*CLI.CS))
+      Chain = DAG.getNode(ISD::DEBUGTRAP, dl, MVT::Other, Chain);
+  }
+
   // Handle result values, copying them out of physregs into vregs that we
   // return.
   return LowerCallResult(Chain, InFlag, CallConv, isVarArg,