[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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257272
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