[Attributor][FIX] Transform invoke of nounwind to call + br %normal_dest
Even if the invoked function may-return, we can replace it with a call
and branch if it is nounwind. We had almost everything in place to do
this but did not which actually caused a crash when we removed the
landingpad from the actually dead unwind block.
Exposed by the IPConstantProp tests.
diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index fa0ea7e..448a2d4 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -2338,7 +2338,8 @@
continue;
const auto &NoReturnAA =
A.getAAFor<AANoReturn>(*this, IRPosition::callsite_function(*CB));
- if (!NoReturnAA.isAssumedNoReturn())
+ bool MayReturn = !NoReturnAA.isAssumedNoReturn();
+ if (MayReturn && (!Invoke2CallAllowed || !isa<InvokeInst>(CB)))
continue;
Instruction *I = const_cast<Instruction *>(DeadEndI);
BasicBlock *BB = I->getParent();
@@ -2361,6 +2362,26 @@
if (AANoUnw.isAssumedNoUnwind()) {
LLVM_DEBUG(dbgs()
<< "[AAIsDead] Replace invoke with call inst\n");
+ CallInst *CI = createCallMatchingInvoke(II);
+ CI->insertBefore(II);
+ CI->takeName(II);
+ II->replaceAllUsesWith(CI);
+
+ // If this is a nounwind + mayreturn invoke we only remove the unwind edge.
+ // This is done by moving the invoke into a new and dead block and connecting
+ // the normal destination of the invoke with a branch that follows the call
+ // replacement we created above.
+ if (MayReturn) {
+ BasicBlock *NewDeadBB = SplitBlock(BB, II, nullptr, nullptr, nullptr, ".i2c");
+ assert(isa<BranchInst>(BB->getTerminator()) &&
+ BB->getTerminator()->getNumSuccessors() == 1 &&
+ BB->getTerminator()->getSuccessor(0) == NewDeadBB);
+ new UnreachableInst(I->getContext(), NewDeadBB);
+ BB->getTerminator()->setOperand(0, NormalDestBB);
+ A.deleteAfterManifest(*II);
+ continue;
+ }
+
// We do not need an invoke (II) but instead want a call followed
// by an unreachable. However, we do not remove II as other
// abstract attributes might have it cached as part of their
@@ -2370,10 +2391,6 @@
// only reached from the current block of II and then not reached
// at all when we insert the unreachable.
SplitBlockPredecessors(NormalDestBB, {BB}, ".i2c");
- CallInst *CI = createCallMatchingInvoke(II);
- CI->insertBefore(II);
- CI->takeName(II);
- II->replaceAllUsesWith(CI);
SplitPos = CI->getNextNode();
}
}