1 files changed, 88 insertions, 0 deletions
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExceptionPrepare.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExceptionPrepare.cpp
new file mode 100644
index 00000000000..837e9576c85
--- /dev/null
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyExceptionPrepare.cpp
@@ -0,0 +1,88 @@
+//=== WebAssemblyExceptionPrepare.cpp - WebAssembly Exception Preparation -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Does various transformations for exception handling.
+///
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssembly.h"
+#include "WebAssemblySubtarget.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "wasm-exception-prepare"
+
+namespace {
+class WebAssemblyExceptionPrepare final : public MachineFunctionPass {
+  StringRef getPassName() const override {
+    return "WebAssembly Prepare Exception";
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  bool replaceFuncletReturns(MachineFunction &MF);
+
+public:
+  static char ID; // Pass identification, replacement for typeid
+  WebAssemblyExceptionPrepare() : MachineFunctionPass(ID) {}
+};
+} // end anonymous namespace
+
+char WebAssemblyExceptionPrepare::ID = 0;
+INITIALIZE_PASS(WebAssemblyExceptionPrepare, DEBUG_TYPE,
+                "WebAssembly Exception Preparation", false, false)
+
+FunctionPass *llvm::createWebAssemblyExceptionPrepare() {
+  return new WebAssemblyExceptionPrepare();
+}
+
+bool WebAssemblyExceptionPrepare::runOnMachineFunction(MachineFunction &MF) {
+  bool Changed = false;
+  if (!MF.getFunction().hasPersonalityFn())
+    return false;
+  Changed |= replaceFuncletReturns(MF);
+  // TODO More transformations will be added
+  return Changed;
+}
+
+bool WebAssemblyExceptionPrepare::replaceFuncletReturns(MachineFunction &MF) {
+  bool Changed = false;
+  const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+
+  for (auto &MBB : MF) {
+    auto Pos = MBB.getFirstTerminator();
+    if (Pos == MBB.end())
+      continue;
+    MachineInstr *TI = &*Pos;
+
+    switch (TI->getOpcode()) {
+    case WebAssembly::CATCHRET: {
+      // Replace a catchret with a branch
+      MachineBasicBlock *TBB = TI->getOperand(0).getMBB();
+      if (!MBB.isLayoutSuccessor(TBB))
+        BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::BR))
+            .addMBB(TBB);
+      TI->eraseFromParent();
+      Changed = true;
+      break;
+    }
+    case WebAssembly::CLEANUPRET: {
+      // Replace a cleanupret with a rethrow
+      BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::RETHROW))
+          .addImm(0);
+      TI->eraseFromParent();
+      Changed = true;
+      break;
+    }
+    }
+  }
+  return Changed;
+}