3 files changed, 110 insertions, 1 deletions
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index 8df2042d68b..417da69f543 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -118,6 +118,7 @@ add_llvm_library(LLVMCodeGen
   TwoAddressInstructionPass.cpp
   UnreachableBlockElim.cpp
   VirtRegMap.cpp
+  WinEHPrepare.cpp
   )
 
 add_dependencies(LLVMCodeGen intrinsics_gen)
diff --git a/llvm/lib/CodeGen/Passes.cpp b/llvm/lib/CodeGen/Passes.cpp
index c66d2131f8f..b9dd0f78c81 100644
--- a/llvm/lib/CodeGen/Passes.cpp
+++ b/llvm/lib/CodeGen/Passes.cpp
@@ -450,9 +450,11 @@ void TargetPassConfig::addPassesToHandleExceptions() {
     // FALLTHROUGH
   case ExceptionHandling::DwarfCFI:
   case ExceptionHandling::ARM:
-  case ExceptionHandling::WinEH:
     addPass(createDwarfEHPass(TM));
     break;
+  case ExceptionHandling::WinEH:
+    addPass(createWinEHPass(TM));
+    break;
   case ExceptionHandling::None:
     addPass(createLowerInvokePass());
 
diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
new file mode 100644
index 00000000000..a01adcd43d0
--- /dev/null
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -0,0 +1,106 @@
+//===-- WinEHPrepare - Prepare exception handling for code generation ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers LLVM IR exception handling into something closer to what the
+// backend wants. It snifs the personality function to see which kind of
+// preparation is necessary. If the personality function uses the Itanium LSDA,
+// this pass delegates to the DWARF EH preparation pass.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Analysis/LibCallSemantics.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/Pass.h"
+#include "llvm/Target/TargetLowering.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "winehprepare"
+
+namespace {
+class WinEHPrepare : public FunctionPass {
+  const TargetMachine *TM;
+  FunctionPass *DwarfPrepare;
+
+public:
+  static char ID; // Pass identification, replacement for typeid.
+  WinEHPrepare(const TargetMachine *TM = nullptr)
+      : FunctionPass(ID), TM(TM), DwarfPrepare(createDwarfEHPass(TM)) {
+    initializeDominatorTreeWrapperPassPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &Fn) override;
+
+  bool doFinalization(Module &M) override;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  const char *getPassName() const override {
+    return "Windows exception handling preparation";
+  }
+};
+} // end anonymous namespace
+
+char WinEHPrepare::ID = 0;
+INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare",
+                   "Prepare Windows exceptions", false, false)
+
+FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
+  return new WinEHPrepare(TM);
+}
+
+static bool isMSVCPersonality(EHPersonality Pers) {
+  return Pers == EHPersonality::MSVC_Win64SEH ||
+         Pers == EHPersonality::MSVC_CXX;
+}
+
+bool WinEHPrepare::runOnFunction(Function &Fn) {
+  SmallVector<LandingPadInst *, 4> LPads;
+  SmallVector<ResumeInst *, 4> Resumes;
+  for (BasicBlock &BB : Fn) {
+    if (auto *LP = BB.getLandingPadInst())
+      LPads.push_back(LP);
+    if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
+      Resumes.push_back(Resume);
+  }
+
+  // No need to prepare functions that lack landing pads.
+  if (LPads.empty())
+    return false;
+
+  // Classify the personality to see what kind of preparation we need.
+  EHPersonality Pers = ClassifyEHPersonality(LPads.back()->getPersonalityFn());
+
+  // Delegate through to the DWARF pass if this is unrecognized.
+  if (!isMSVCPersonality(Pers))
+    return DwarfPrepare->runOnFunction(Fn);
+
+  // FIXME: Cleanups are unimplemented. Replace them with calls to @llvm.trap.
+  if (Resumes.empty())
+    return false;
+
+  Function *Trap =
+      Intrinsic::getDeclaration(Fn.getParent(), Intrinsic::trap, None);
+  for (ResumeInst *Resume : Resumes) {
+    IRBuilder<>(Resume).CreateUnreachable();
+    Resume->eraseFromParent();
+  }
+
+  return true;
+}
+
+bool WinEHPrepare::doFinalization(Module &M) {
+  return DwarfPrepare->doFinalization(M);
+}
+
+void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
+  DwarfPrepare->getAnalysisUsage(AU);
+}