[WebAssembly] Fix a bug deleting instruction in a ranged for loop

Summary: We shouldn't delete elements while iterating a ranged for loop.

Reviewers: dschuff

Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58519

llvm-svn: 354844

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
index 2962de47653..65958e00eb3 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
@@ -222,18 +222,22 @@ bool WebAssemblyLateEHPrepare::addExceptionExtraction(MachineFunction &MF) {
   const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
   auto *EHInfo = MF.getWasmEHFuncInfo();
   SmallVector<MachineInstr *, 16> ExtractInstrs;
+  SmallVector<MachineInstr *, 8> ToDelete;
   for (auto &MBB : MF) {
     for (auto &MI : MBB) {
       if (MI.getOpcode() == WebAssembly::EXTRACT_EXCEPTION_I32) {
         if (MI.getOperand(0).isDead())
-          MI.eraseFromParent();
+          ToDelete.push_back(&MI);
         else
           ExtractInstrs.push_back(&MI);
       }
     }
   }
+  bool Changed = !ToDelete.empty() || !ExtractInstrs.empty();
+  for (auto *MI : ToDelete)
+    MI->eraseFromParent();
   if (ExtractInstrs.empty())
-    return false;
+    return Changed;
 
   // Find terminate pads.
   SmallSet<MachineBasicBlock *, 8> TerminatePads;