[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
llvm · Feb 26, 2019 · d2a56ac · d2a56ac
1 parent f0d2733
commit d2a56ac
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Showing 2 changed files with 26 additions and 2 deletions.
diff --git 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;

diff --git a/llvm/test/CodeGen/WebAssembly/exception.ll b/llvm/test/CodeGen/WebAssembly/exception.ll
@@ -340,6 +340,26 @@ try.cont:                                         ; preds = %entry, %catch.start
   ret void
 }
 
+; When the result of @llvm.wasm.get.exception is not used. This is created to
+; fix a bug in LateEHPrepare and this should not crash.
+define void @test_get_exception_wo_use() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+entry:
+  invoke void @foo()
+          to label %try.cont unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %0 = catchswitch within none [label %catch.start] unwind to caller
+
+catch.start:                                      ; preds = %catch.dispatch
+  %1 = catchpad within %0 [i8* null]
+  %2 = call i8* @llvm.wasm.get.exception(token %1)
+  %3 = call i32 @llvm.wasm.get.ehselector(token %1)
+  catchret from %1 to label %try.cont
+
+try.cont:                                         ; preds = %entry, %catch.start
+  ret void
+}
+
 declare void @foo()
 declare void @bar(i32*)
 declare i32 @__gxx_wasm_personality_v0(...)