[SEH] Reimplement x64 SEH using WinEHPrepare

This now emits simple, unoptimized xdata tables for __C_specific_handler
based on the handlers listed in @llvm.eh.actions calls produced by
WinEHPrepare.

This adds support for running __finally blocks when exceptions are
thrown, and removes the old landingpad fan-in codepath.

I ran some manual execution tests on small basic test cases with and
without optimization, as well as on Chrome base_unittests, which uses a
small amount of SEH.  I'm sure there are bugs, and we may need to
revert.

llvm-svn: 235154

2 files changed, 78 insertions, 65 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index 4b8ae32e9a5..bb40326ba2d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -270,12 +270,21 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
   }
 
   // Mark landing pad blocks.
-  for (BB = Fn->begin(); BB != EB; ++BB)
+  const LandingPadInst *LP = nullptr;
+  for (BB = Fn->begin(); BB != EB; ++BB) {
     if (const auto *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
       MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
+    if (BB->isLandingPad())
+      LP = BB->getLandingPadInst();
+  }
 
-  // Calculate EH numbers for WinEH.
-  if (fn.hasFnAttribute("wineh-parent")) {
+  // Calculate EH numbers for MSVC C++ EH and save SEH handlers if necessary.
+  EHPersonality Personality = EHPersonality::Unknown;
+  if (LP)
+    Personality = classifyEHPersonality(LP->getPersonalityFn());
+  if (Personality == EHPersonality::MSVC_Win64SEH) {
+    addSEHHandlersForLPads();
+  } else if (Personality == EHPersonality::MSVC_CXX) {
     const Function *WinEHParentFn = MMI.getWinEHParent(&fn);
     WinEHFuncInfo &FI = MMI.getWinEHFuncInfo(WinEHParentFn);
     if (FI.LandingPadStateMap.empty()) {
@@ -287,6 +296,47 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
   }
 }
 
+void FunctionLoweringInfo::addSEHHandlersForLPads() {
+  MachineModuleInfo &MMI = MF->getMMI();
+
+  // Iterate over all landing pads with llvm.eh.actions calls.
+  for (const BasicBlock &BB : *Fn) {
+    const LandingPadInst *LP = BB.getLandingPadInst();
+    if (!LP)
+      continue;
+    const IntrinsicInst *ActionsCall =
+        dyn_cast<IntrinsicInst>(LP->getNextNode());
+    if (!ActionsCall ||
+        ActionsCall->getIntrinsicID() != Intrinsic::eh_actions)
+      continue;
+
+    // Parse the llvm.eh.actions call we found.
+    MachineBasicBlock *LPadMBB = MBBMap[LP->getParent()];
+    SmallVector<ActionHandler *, 4> Actions;
+    parseEHActions(ActionsCall, Actions);
+
+    // Iterate EH actions from most to least precedence, which means
+    // iterating in reverse.
+    for (auto I = Actions.rbegin(), E = Actions.rend(); I != E; ++I) {
+      ActionHandler *Action = *I;
+      if (auto *CH = dyn_cast<CatchHandler>(Action)) {
+        const auto *Filter =
+            dyn_cast<Function>(CH->getSelector()->stripPointerCasts());
+        assert((Filter || CH->getSelector()->isNullValue()) &&
+               "expected function or catch-all");
+        const auto *RecoverBA =
+            cast<BlockAddress>(CH->getHandlerBlockOrFunc());
+        MMI.addSEHCatchHandler(LPadMBB, Filter, RecoverBA);
+      } else {
+        assert(isa<CleanupHandler>(Action));
+        const auto *Fini = cast<Function>(Action->getHandlerBlockOrFunc());
+        MMI.addSEHCleanupHandler(LPadMBB, Fini);
+      }
+    }
+    DeleteContainerPointers(Actions);
+  }
+}
+
 void WinEHNumbering::createUnwindMapEntry(int ToState, ActionHandler *AH) {
   WinEHUnwindMapEntry UME;
   UME.ToState = ToState;
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 1e116dddafa..0478c7382f2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -911,7 +911,7 @@ void SelectionDAGISel::DoInstructionSelection() {
 
 /// PrepareEHLandingPad - Emit an EH_LABEL, set up live-in registers, and
 /// do other setup for EH landing-pad blocks.
-void SelectionDAGISel::PrepareEHLandingPad() {
+bool SelectionDAGISel::PrepareEHLandingPad() {
   MachineBasicBlock *MBB = FuncInfo->MBB;
 
   const TargetRegisterClass *PtrRC = TLI->getRegClassFor(TLI->getPointerTy());
@@ -937,70 +937,28 @@ void SelectionDAGISel::PrepareEHLandingPad() {
 
   if (isMSVCEHPersonality(Personality)) {
     SmallVector<MachineBasicBlock *, 4> ClauseBBs;
-    const IntrinsicInst *Actions =
+    const IntrinsicInst *ActionsCall =
         dyn_cast<IntrinsicInst>(LLVMBB->getFirstInsertionPt());
     // Get all invoke BBs that unwind to this landingpad.
     SmallVector<MachineBasicBlock *, 4> InvokeBBs(MBB->pred_begin(),
                                                   MBB->pred_end());
-    if (Actions && Actions->getIntrinsicID() == Intrinsic::eh_actions) {
-      // If this is a call to llvm.eh.actions followed by indirectbr, then we've
-      // run WinEHPrepare, and we should remove this block from the machine CFG.
-      // Mark the targets of the indirectbr as landingpads instead.
-      for (const BasicBlock *LLVMSucc : successors(LLVMBB)) {
-        MachineBasicBlock *ClauseBB = FuncInfo->MBBMap[LLVMSucc];
-        // Add the edge from the invoke to the clause.
-        for (MachineBasicBlock *InvokeBB : InvokeBBs)
-          InvokeBB->addSuccessor(ClauseBB);
-      }
-    } else {
-      // Otherwise, we haven't done the preparation, and we need to invent some
-      // clause basic blocks that branch into the landingpad.
-      // FIXME: Remove this code once SEH preparation works.
-
-      // Make virtual registers and a series of labels that fill in values for
-      // the clauses.
-      auto &RI = MF->getRegInfo();
-      FuncInfo->ExceptionSelectorVirtReg = RI.createVirtualRegister(PtrRC);
-
-      // Emit separate machine basic blocks with separate labels for each clause
-      // before the main landing pad block.
-      MachineInstrBuilder SelectorPHI = BuildMI(
-          *MBB, MBB->begin(), SDB->getCurDebugLoc(),
-          TII->get(TargetOpcode::PHI), FuncInfo->ExceptionSelectorVirtReg);
-      for (unsigned I = 0, E = LPadInst->getNumClauses(); I != E; ++I) {
-        // Skip filter clauses, we can't implement them.
-        if (LPadInst->isFilter(I))
-          continue;
-
-        MachineBasicBlock *ClauseBB = MF->CreateMachineBasicBlock(LLVMBB);
-        MF->insert(MBB, ClauseBB);
-
-        // Add the edge from the invoke to the clause.
-        for (MachineBasicBlock *InvokeBB : InvokeBBs)
-          InvokeBB->addSuccessor(ClauseBB);
-
-        // Mark the clause as a landing pad or MI passes will delete it.
-        ClauseBB->setIsLandingPad();
-
-        GlobalValue *ClauseGV = ExtractTypeInfo(LPadInst->getClause(I));
-
-        // Start the BB with a label.
-        MCSymbol *ClauseLabel = MF->getMMI().addClauseForLandingPad(MBB);
-        BuildMI(*ClauseBB, ClauseBB->begin(), SDB->getCurDebugLoc(), II)
-            .addSym(ClauseLabel);
-
-        // Construct a simple BB that defines a register with the typeid
-        // constant.
-        FuncInfo->MBB = ClauseBB;
-        FuncInfo->InsertPt = ClauseBB->end();
-        unsigned VReg = SDB->visitLandingPadClauseBB(ClauseGV, MBB);
-        CurDAG->setRoot(SDB->getRoot());
-        SDB->clear();
-        CodeGenAndEmitDAG();
+    if (!ActionsCall || ActionsCall->getIntrinsicID() != Intrinsic::eh_actions) {
+      assert(isa<UnreachableInst>(LLVMBB->getFirstInsertionPt()) &&
+             "found landingpad without unreachable or llvm.eh.actions");
+      return false;
+    }
 
-        // Add the typeid virtual register to the phi in the main landing pad.
-        SelectorPHI.addReg(VReg).addMBB(ClauseBB);
-      }
+    // If this is a call to llvm.eh.actions followed by indirectbr, then we've
+    // run WinEHPrepare, and we should remove this block from the machine CFG.
+    // Mark the targets of the indirectbr as landingpads instead.
+    for (const BasicBlock *LLVMSucc : successors(LLVMBB)) {
+      MachineBasicBlock *ClauseBB = FuncInfo->MBBMap[LLVMSucc];
+      // Add the edge from the invoke to the clause.
+      for (MachineBasicBlock *InvokeBB : InvokeBBs)
+        InvokeBB->addSuccessor(ClauseBB);
+
+      // Mark the clause as a landing pad or MI passes will delete it.
+      ClauseBB->setIsLandingPad();
     }
 
     // Remove the edge from the invoke to the lpad.
@@ -1017,7 +975,9 @@ void SelectionDAGISel::PrepareEHLandingPad() {
       WinEHFuncInfo &FI = MF->getMMI().getWinEHFuncInfo(MF->getFunction());
       MF->getMMI().addWinEHState(MBB, FI.LandingPadStateMap[LPadInst]);
     }
-    return;
+
+    // Don't select instructions for landing pads using llvm.eh.actions.
+    return false;
   }
 
   // Mark exception register as live in.
@@ -1027,6 +987,8 @@ void SelectionDAGISel::PrepareEHLandingPad() {
   // Mark exception selector register as live in.
   if (unsigned Reg = TLI->getExceptionSelectorRegister())
     FuncInfo->ExceptionSelectorVirtReg = MBB->addLiveIn(Reg, PtrRC);
+
+  return true;
 }
 
 /// isFoldedOrDeadInstruction - Return true if the specified instruction is
@@ -1197,7 +1159,8 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
     FuncInfo->ExceptionPointerVirtReg = 0;
     FuncInfo->ExceptionSelectorVirtReg = 0;
     if (LLVMBB->isLandingPad())
-      PrepareEHLandingPad();
+      if (!PrepareEHLandingPad())
+        continue;
 
     // Before doing SelectionDAG ISel, see if FastISel has been requested.
     if (FastIS) {