Revert "Revert "Revert r248959, "[WinEH] Emit int3 after noreturn calls on Win64"""
This reverts commit r249794.
Apparently my checkouts are full of unexpected surprises today.
llvm-svn: 249796
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9954b6c..fae877a 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -2951,20 +2951,6 @@
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 {
@@ -3470,15 +3456,6 @@
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,
diff --git a/llvm/lib/Target/X86/X86TargetMachine.cpp b/llvm/lib/Target/X86/X86TargetMachine.cpp
index d318244..2e869eb 100644
--- a/llvm/lib/Target/X86/X86TargetMachine.cpp
+++ b/llvm/lib/Target/X86/X86TargetMachine.cpp
@@ -110,6 +110,13 @@
OL),
TLOF(createTLOF(getTargetTriple())),
Subtarget(TT, CPU, FS, *this, Options.StackAlignmentOverride) {
+ // Windows stack unwinder gets confused when execution flow "falls through"
+ // after a call to 'noreturn' function.
+ // To prevent that, we emit a trap for 'unreachable' IR instructions.
+ // (which on X86, happens to be the 'ud2' instruction)
+ if (Subtarget.isTargetWin64())
+ this->Options.TrapUnreachable = true;
+
// By default (and when -ffast-math is on), enable estimate codegen for
// everything except scalar division. By default, use 1 refinement step for
// all operations. Defaults may be overridden by using command-line options.