[PATCH] D52902: [WebAssembly] Don't modify preds/succs iterators while erasing from them

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
aheejin added a reviewer: dschuff.
Herald added subscribers: llvm-commits, sunfish, jgravelle-google, sbc100.

This caused out-of-bound bugs. Found by
`-DLLVM_ENABLE_EXPENSIVE_CHECKS=ON`.


Repository:
  rL LLVM

https://reviews.llvm.org/D52902

Files:
  lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp


Index: lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
===================================================================
--- lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
+++ lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
@@ -91,12 +91,17 @@
   SmallVector<MachineBasicBlock *, 8> WL(MBBs.begin(), MBBs.end());
   while (!WL.empty()) {
     MachineBasicBlock *MBB = WL.pop_back_val();
+    SmallVector<MachineBasicBlock *, 4> Preds, Succs;
     for (auto *Pred : MBB->predecessors())
+      Preds.push_back(Pred);
+    for (auto *Pred : Preds)
       Pred->removeSuccessor(MBB);
     for (auto *Succ : MBB->successors()) {
+      Succs.push_back(Succ);
       WL.push_back(Succ);
-      MBB->removeSuccessor(Succ);
     }
+    for (auto *Succ : Succs)
+      MBB->removeSuccessor(Succ);
     MBB->eraseFromParent();
   }
 }


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