[PATCH] D16319: [Inliner/WinEH] Honor implicit nounwinds

[David Majnemer via llvm-commits]

majnemer accepted this revision.
majnemer added a comment.
This revision is now accepted and ready to land.

LGTM, thanks for fixing this!


================
Comment at: lib/Transforms/Utils/InlineFunction.cpp:615-624
@@ +614,12 @@
+        Value *UnwindDestToken;
+        if (auto *ParentPad =
+                dyn_cast<Instruction>(CatchSwitch->getParentPad())) {
+          // This catchswitch is nested inside another funclet.  If that
+          // funclet has an unwind destination within the inlinee, then
+          // unwinding out of this catchswitch would be UB.  Rewriting this
+          // catchswitch to unwind to the inlined invoke's unwind dest would
+          // give the parent funclet multiple unwind destinations, which is
+          // something that subsequent EH table generation can't handle and
+          // that the veirifer rejects.  So when we see such a call, leave it
+          // as "unwind to caller".
+          UnwindDestToken = getUnwindDestToken(ParentPad, FuncletUnwindMap);
----------------
JosephTremoulet wrote:
> No, this happens when you have an unwind-to-caller catchswitch nested inside an outer pad which unwinds somewhere else in the inlinee.  E.g. if you start with
> 
> ```
> define void inlinee() {
>   ...
>   %parent = cleanuppad within none []
> ...
>   %current = catchswitch within %parent [label ...] unwind label %sibling
> ...
> sibling:
>   %sib = cleanuppad within %parent []
>   unreachable
> ...
>   cleanupret from %parent unwind label %uncle
> ```
> 
> then SimplifyUnreachable could turn that into
> 
> ```
> define void inlinee() {
>   ...
>   %parent = cleanuppad within none []
> ...
>   %current = catchswitch within %parent [label ...] unwind to caller
> ...
>   cleanupret from %parent unwind label %uncle
> ```
> 
> and //that's// the case this code is dealing with.
Would we need to do this if we had catchswitches which could be annotated as nounwind?


http://reviews.llvm.org/D16319