8 files changed, 199 insertions, 3 deletions
diff --git a/llvm/include/llvm/CodeGen/Passes.h b/llvm/include/llvm/CodeGen/Passes.h
index bff58e12fe5..7e5e9008320 100644
--- a/llvm/include/llvm/CodeGen/Passes.h
+++ b/llvm/include/llvm/CodeGen/Passes.h
@@ -573,6 +573,10 @@ namespace llvm {
   /// adapted to code generation.  Required if using dwarf exception handling.
   FunctionPass *createDwarfEHPass(const TargetMachine *TM);
 
+  /// createWinEHPass - Prepares personality functions used by MSVC on Windows,
+  /// in addition to the Itanium LSDA based personalities.
+  FunctionPass *createWinEHPass(const TargetMachine *TM);
+
   /// createSjLjEHPreparePass - This pass adapts exception handling code to use
   /// the GCC-style builtin setjmp/longjmp (sjlj) to handling EH control flow.
   ///
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index 91884097504..6a6d48cc42f 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -289,6 +289,7 @@ void initializeStackMapLivenessPass(PassRegistry&);
 void initializeMachineCombinerPass(PassRegistry &);
 void initializeLoadCombinePass(PassRegistry&);
 void initializeRewriteSymbolsPass(PassRegistry&);
+void initializeWinEHPreparePass(PassRegistry&);
 }
 
 #endif
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);
+}
diff --git a/llvm/test/CodeGen/X86/seh-safe-div.ll b/llvm/test/CodeGen/X86/seh-safe-div.ll
index e911df04ded..e294f24f28b 100644
--- a/llvm/test/CodeGen/X86/seh-safe-div.ll
+++ b/llvm/test/CodeGen/X86/seh-safe-div.ll
@@ -96,8 +96,9 @@ __try.cont:
 ; CHECK: movl $-2, [[rloc]]
 ; CHECK: jmp .LBB0_7
 
-; FIXME: EH preparation should not call _Unwind_Resume.
-; CHECK: callq _Unwind_Resume
+; FIXME: EH preparation should eliminate the 'resume' instr and we should not do
+; the previous 'cmp;jeq'.
+; CHECK-NOT: _Unwind_Resume
 ; CHECK: ud2
 
 ; CHECK: .seh_handlerdata
diff --git a/llvm/test/CodeGen/X86/win_eh_prepare.ll b/llvm/test/CodeGen/X86/win_eh_prepare.ll
new file mode 100644
index 00000000000..f96fed5095f
--- /dev/null
+++ b/llvm/test/CodeGen/X86/win_eh_prepare.ll
@@ -0,0 +1,80 @@
+; RUN: opt -S -winehprepare -mtriple x86_64-pc-windows-msvc < %s | FileCheck %s
+
+; FIXME: Add and test outlining here.
+
+declare void @maybe_throw()
+
+@_ZTIi = external constant i8*
+@g = external global i32
+
+declare i32 @__C_specific_handler(...)
+declare i32 @__gxx_personality_seh0(...)
+declare i32 @llvm.eh.typeid.for(i8*) readnone nounwind
+
+define i32 @use_seh() {
+entry:
+  invoke void @maybe_throw()
+      to label %cont unwind label %lpad
+
+cont:
+  ret i32 0
+
+lpad:
+  %ehvals = landingpad { i8*, i32 } personality i32 (...)* @__C_specific_handler
+      cleanup
+      catch i8* bitcast (i32 (i8*, i8*)* @filt_g to i8*)
+  %ehsel = extractvalue { i8*, i32 } %ehvals, 1
+  %filt_g_sel = call i32 @llvm.eh.typeid.for(i8* bitcast (i32 (i8*, i8*)* @filt_g to i8*))
+  %matches = icmp eq i32 %ehsel, %filt_g_sel
+  br i1 %matches, label %ret1, label %eh.resume
+
+ret1:
+  ret i32 1
+
+eh.resume:
+  resume { i8*, i32 } %ehvals
+}
+
+define internal i32 @filt_g(i8*, i8*) {
+  %g = load i32* @g
+  ret i32 %g
+}
+
+; CHECK-LABEL: define i32 @use_seh()
+; CHECK: invoke void @maybe_throw()
+; CHECK-NEXT: to label %cont unwind label %lpad
+; CHECK: eh.resume:
+; CHECK-NEXT: unreachable
+
+
+; A MinGW64-ish EH style. It could happen if a binary uses both MSVC CRT and
+; mingw CRT and is linked with LTO.
+define i32 @use_gcc() {
+entry:
+  invoke void @maybe_throw()
+      to label %cont unwind label %lpad
+
+cont:
+  ret i32 0
+
+lpad:
+  %ehvals = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_seh0
+      cleanup
+      catch i8* bitcast (i8** @_ZTIi to i8*)
+  %ehsel = extractvalue { i8*, i32 } %ehvals, 1
+  %filt_g_sel = call i32 @llvm.eh.typeid.for(i8* bitcast (i32 (i8*, i8*)* @filt_g to i8*))
+  %matches = icmp eq i32 %ehsel, %filt_g_sel
+  br i1 %matches, label %ret1, label %eh.resume
+
+ret1:
+  ret i32 1
+
+eh.resume:
+  resume { i8*, i32 } %ehvals
+}
+
+; CHECK-LABEL: define i32 @use_gcc()
+; CHECK: invoke void @maybe_throw()
+; CHECK-NEXT: to label %cont unwind label %lpad
+; CHECK: eh.resume:
+; CHECK: call void @_Unwind_Resume(i8* %exn.obj)
diff --git a/llvm/tools/opt/opt.cpp b/llvm/tools/opt/opt.cpp
index 3cd07c53e5d..6083e7a70a8 100644
--- a/llvm/tools/opt/opt.cpp
+++ b/llvm/tools/opt/opt.cpp
@@ -322,6 +322,7 @@ int main(int argc, char **argv) {
   initializeCodeGenPreparePass(Registry);
   initializeAtomicExpandPass(Registry);
   initializeRewriteSymbolsPass(Registry);
+  initializeWinEHPreparePass(Registry);
 
 #ifdef LINK_POLLY_INTO_TOOLS
   polly::initializePollyPasses(Registry);