[WinEH] Verify unwind edges against EH pad tree
Summary:
Funclet EH personalities require a tree-like nesting among funclets
(enforced by the ParentPad linkage in the IR), and also require that
unwind edges conform to certain rules with respect to the tree:
- An unwind edge may exit 0 or more ancestor pads
- An unwind edge must enter exactly one EH pad, which must be distinct
from any exited pads
- A cleanupret's edge must exit its cleanuppad
Describe these rules in the LangRef, and enforce them in the verifier.
Reviewers: rnk, majnemer, andrew.w.kaylor
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15961
llvm-svn: 257272
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 64d7575..44ced48 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -2895,6 +2895,13 @@
visitInstruction(IVI);
}
+static Value *getParentPad(Value *EHPad) {
+ if (auto *FPI = dyn_cast<FuncletPadInst>(EHPad))
+ return FPI->getParentPad();
+
+ return cast<CatchSwitchInst>(EHPad)->getParentPad();
+}
+
void Verifier::visitEHPadPredecessors(Instruction &I) {
assert(I.isEHPad());
@@ -2925,13 +2932,39 @@
return;
}
+ // Verify that each pred has a legal terminator with a legal to/from EH
+ // pad relationship.
+ Instruction *ToPad = &I;
+ Value *ToPadParent = getParentPad(ToPad);
for (BasicBlock *PredBB : predecessors(BB)) {
TerminatorInst *TI = PredBB->getTerminator();
+ Value *FromPad;
if (auto *II = dyn_cast<InvokeInst>(TI)) {
Assert(II->getUnwindDest() == BB && II->getNormalDest() != BB,
- "EH pad must be jumped to via an unwind edge", &I, II);
- } else if (!isa<CleanupReturnInst>(TI) && !isa<CatchSwitchInst>(TI)) {
- Assert(false, "EH pad must be jumped to via an unwind edge", &I, TI);
+ "EH pad must be jumped to via an unwind edge", ToPad, II);
+ if (auto Bundle = II->getOperandBundle(LLVMContext::OB_funclet))
+ FromPad = Bundle->Inputs[0];
+ else
+ FromPad = ConstantTokenNone::get(II->getContext());
+ } else if (auto *CRI = dyn_cast<CleanupReturnInst>(TI)) {
+ FromPad = CRI->getCleanupPad();
+ Assert(FromPad != ToPadParent, "A cleanupret must exit its cleanup", CRI);
+ } else if (auto *CSI = dyn_cast<CatchSwitchInst>(TI)) {
+ FromPad = CSI;
+ } else {
+ Assert(false, "EH pad must be jumped to via an unwind edge", ToPad, TI);
+ }
+
+ // The edge may exit from zero or more nested pads.
+ for (;; FromPad = getParentPad(FromPad)) {
+ Assert(FromPad != ToPad,
+ "EH pad cannot handle exceptions raised within it", FromPad, TI);
+ if (FromPad == ToPadParent) {
+ // This is a legal unwind edge.
+ break;
+ }
+ Assert(!isa<ConstantTokenNone>(FromPad),
+ "A single unwind edge may only enter one EH pad", TI);
}
}
}