[SSP] Remove llvm.stackprotectorcheck.

This is a cleanup patch for SSP support in LLVM. There is no functional change.
llvm.stackprotectorcheck is not needed, because SelectionDAG isn't
actually lowering it in SelectBasicBlock; rather, it adds check code in
FinishBasicBlock, ignoring the position where the intrinsic is inserted
(See FindSplitPointForStackProtector()).

llvm-svn: 265851

5 files changed, 76 insertions, 125 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 5ad42936169..27d24222aff 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2014,7 +2014,10 @@ void SelectionDAGBuilder::visitSPDescriptorParent(StackProtectorDescriptor &SPD,
   MachineFrameInfo *MFI = ParentBB->getParent()->getFrameInfo();
   int FI = MFI->getStackProtectorIndex();
 
-  const Value *IRGuard = SPD.getGuard();
+  const Module &M = *ParentBB->getParent()->getFunction()->getParent();
+  const Value *IRGuard = TLI.getSDStackGuard(M);
+  assert(IRGuard && "Currently there must be an IR guard in order to use "
+                    "SelectionDAG SSP");
   SDValue GuardPtr = getValue(IRGuard);
   SDValue StackSlotPtr = DAG.getFrameIndex(FI, PtrTy);
 
@@ -5517,18 +5520,6 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
   case Intrinsic::invariant_end:
     // Discard region information.
     return nullptr;
-  case Intrinsic::stackprotectorcheck: {
-    // Do not actually emit anything for this basic block. Instead we initialize
-    // the stack protector descriptor and export the guard variable so we can
-    // access it in FinishBasicBlock.
-    const BasicBlock *BB = I.getParent();
-    SPDescriptor.initialize(BB, FuncInfo.MBBMap[BB], I);
-    ExportFromCurrentBlock(SPDescriptor.getGuard());
-
-    // Flush our exports since we are going to process a terminator.
-    (void)getControlRoot();
-    return nullptr;
-  }
   case Intrinsic::clear_cache:
     return TLI.getClearCacheBuiltinName();
   case Intrinsic::donothing:
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 2d2002680ba..47d8870cd95 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -464,29 +464,25 @@ private:
   ///        the same function, use the same failure basic block).
   class StackProtectorDescriptor {
   public:
-    StackProtectorDescriptor() : ParentMBB(nullptr), SuccessMBB(nullptr),
-                                 FailureMBB(nullptr), Guard(nullptr),
-                                 GuardReg(0) { }
+    StackProtectorDescriptor()
+        : ParentMBB(nullptr), SuccessMBB(nullptr), FailureMBB(nullptr),
+          GuardReg(0) {}
 
     /// Returns true if all fields of the stack protector descriptor are
     /// initialized implying that we should/are ready to emit a stack protector.
     bool shouldEmitStackProtector() const {
-      return ParentMBB && SuccessMBB && FailureMBB && Guard;
+      return ParentMBB && SuccessMBB && FailureMBB;
     }
 
     /// Initialize the stack protector descriptor structure for a new basic
     /// block.
-    void initialize(const BasicBlock *BB,
-                    MachineBasicBlock *MBB,
-                    const CallInst &StackProtCheckCall) {
+    void initialize(const BasicBlock *BB, MachineBasicBlock *MBB) {
       // Make sure we are not initialized yet.
       assert(!shouldEmitStackProtector() && "Stack Protector Descriptor is "
              "already initialized!");
       ParentMBB = MBB;
       SuccessMBB = AddSuccessorMBB(BB, MBB, /* IsLikely */ true);
       FailureMBB = AddSuccessorMBB(BB, MBB, /* IsLikely */ false, FailureMBB);
-      if (!Guard)
-        Guard = StackProtCheckCall.getArgOperand(0);
     }
 
     /// Reset state that changes when we handle different basic blocks.
@@ -515,14 +511,12 @@ private:
     /// always the same.
     void resetPerFunctionState() {
       FailureMBB = nullptr;
-      Guard = nullptr;
       GuardReg = 0;
     }
 
     MachineBasicBlock *getParentMBB() { return ParentMBB; }
     MachineBasicBlock *getSuccessMBB() { return SuccessMBB; }
     MachineBasicBlock *getFailureMBB() { return FailureMBB; }
-    const Value *getGuard() { return Guard; }
 
     unsigned getGuardReg() const { return GuardReg; }
     void setGuardReg(unsigned R) { GuardReg = R; }
@@ -545,10 +539,6 @@ private:
     /// contain a call to __stack_chk_fail().
     MachineBasicBlock *FailureMBB;
 
-    /// The guard variable which we will compare against the stored value in the
-    /// stack protector stack slot.
-    const Value *Guard;
-
     /// The virtual register holding the stack guard value.
     unsigned GuardReg;
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index e9cb6b43214..b0212c157c5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -11,7 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/CodeGen/GCStrategy.h"
+#include "llvm/CodeGen/SelectionDAG.h"
 #include "ScheduleDAGSDNodes.h"
 #include "SelectionDAGBuilder.h"
 #include "llvm/ADT/PostOrderIterator.h"
@@ -25,6 +25,7 @@
 #include "llvm/CodeGen/FastISel.h"
 #include "llvm/CodeGen/FunctionLoweringInfo.h"
 #include "llvm/CodeGen/GCMetadata.h"
+#include "llvm/CodeGen/GCStrategy.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -32,8 +33,8 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/ScheduleHazardRecognizer.h"
 #include "llvm/CodeGen/SchedulerRegistry.h"
-#include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/SelectionDAGISel.h"
+#include "llvm/CodeGen/StackProtector.h"
 #include "llvm/CodeGen/WinEHFuncInfo.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfo.h"
@@ -377,6 +378,8 @@ SelectionDAGISel::~SelectionDAGISel() {
 void SelectionDAGISel::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<AAResultsWrapperPass>();
   AU.addRequired<GCModuleInfo>();
+  AU.addRequired<StackProtector>();
+  AU.addPreserved<StackProtector>();
   AU.addPreserved<GCModuleInfo>();
   AU.addRequired<TargetLibraryInfoWrapperPass>();
   if (UseMBPI && OptLevel != CodeGenOpt::None)
@@ -1476,6 +1479,8 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
         LowerArguments(Fn);
       }
     }
+    if (getAnalysis<StackProtector>().shouldEmitSDCheck(*LLVMBB))
+      SDB->SPDescriptor.initialize(LLVMBB, FuncInfo->MBBMap[LLVMBB]);
 
     if (Begin != BI)
       ++NumDAGBlocks;
diff --git a/llvm/lib/CodeGen/StackProtector.cpp b/llvm/lib/CodeGen/StackProtector.cpp
index 23ae672944d..3ea56d85fe5 100644
--- a/llvm/lib/CodeGen/StackProtector.cpp
+++ b/llvm/lib/CodeGen/StackProtector.cpp
@@ -89,6 +89,8 @@ bool StackProtector::runOnFunction(Function &Fn) {
       getAnalysisIfAvailable<DominatorTreeWrapperPass>();
   DT = DTWP ? &DTWP->getDomTree() : nullptr;
   TLI = TM->getSubtargetImpl(Fn)->getTargetLowering();
+  HasPrologue = false;
+  HasIRCheck = false;
 
   Attribute Attr = Fn.getFnAttribute("stack-protector-buffer-size");
   if (Attr.isStringAttribute() &&
@@ -200,11 +202,21 @@ bool StackProtector::HasAddressTaken(const Instruction *AI) {
 bool StackProtector::RequiresStackProtector() {
   bool Strong = false;
   bool NeedsProtector = false;
+  for (const BasicBlock &BB : *F)
+    for (const Instruction &I : BB)
+      if (const CallInst *CI = dyn_cast<CallInst>(&I))
+        if (CI->getCalledFunction() ==
+            Intrinsic::getDeclaration(F->getParent(),
+                                      Intrinsic::stackprotector))
+          HasPrologue = true;
+
   if (F->hasFnAttribute(Attribute::StackProtectReq)) {
     NeedsProtector = true;
     Strong = true; // Use the same heuristic as strong to determine SSPLayout
   } else if (F->hasFnAttribute(Attribute::StackProtectStrong))
     Strong = true;
+  else if (HasPrologue)
+    NeedsProtector = true;
   else if (!F->hasFnAttribute(Attribute::StackProtect))
     return false;
 
@@ -256,68 +268,6 @@ bool StackProtector::RequiresStackProtector() {
   return NeedsProtector;
 }
 
-static bool InstructionWillNotHaveChain(const Instruction *I) {
-  return !I->mayHaveSideEffects() && !I->mayReadFromMemory() &&
-         isSafeToSpeculativelyExecute(I);
-}
-
-/// Identify if RI has a previous instruction in the "Tail Position" and return
-/// it. Otherwise return 0.
-///
-/// This is based off of the code in llvm::isInTailCallPosition. The difference
-/// is that it inverts the first part of llvm::isInTailCallPosition since
-/// isInTailCallPosition is checking if a call is in a tail call position, and
-/// we are searching for an unknown tail call that might be in the tail call
-/// position. Once we find the call though, the code uses the same refactored
-/// code, returnTypeIsEligibleForTailCall.
-static CallInst *FindPotentialTailCall(BasicBlock *BB, ReturnInst *RI,
-                                       const TargetLoweringBase *TLI) {
-  // Establish a reasonable upper bound on the maximum amount of instructions we
-  // will look through to find a tail call.
-  unsigned SearchCounter = 0;
-  const unsigned MaxSearch = 4;
-  bool NoInterposingChain = true;
-
-  for (BasicBlock::reverse_iterator I = std::next(BB->rbegin()), E = BB->rend();
-       I != E && SearchCounter < MaxSearch; ++I) {
-    Instruction *Inst = &*I;
-
-    // Skip over debug intrinsics and do not allow them to affect our MaxSearch
-    // counter.
-    if (isa<DbgInfoIntrinsic>(Inst))
-      continue;
-
-    // If we find a call and the following conditions are satisifed, then we
-    // have found a tail call that satisfies at least the target independent
-    // requirements of a tail call:
-    //
-    // 1. The call site has the tail marker.
-    //
-    // 2. The call site either will not cause the creation of a chain or if a
-    // chain is necessary there are no instructions in between the callsite and
-    // the call which would create an interposing chain.
-    //
-    // 3. The return type of the function does not impede tail call
-    // optimization.
-    if (CallInst *CI = dyn_cast<CallInst>(Inst)) {
-      if (CI->isTailCall() &&
-          (InstructionWillNotHaveChain(CI) || NoInterposingChain) &&
-          returnTypeIsEligibleForTailCall(BB->getParent(), CI, RI, *TLI))
-        return CI;
-    }
-
-    // If we did not find a call see if we have an instruction that may create
-    // an interposing chain.
-    NoInterposingChain =
-        NoInterposingChain && InstructionWillNotHaveChain(Inst);
-
-    // Increment max search.
-    SearchCounter++;
-  }
-
-  return nullptr;
-}
-
 /// Insert code into the entry block that stores the __stack_chk_guard
 /// variable onto the stack:
 ///
@@ -329,29 +279,25 @@ static CallInst *FindPotentialTailCall(BasicBlock *BB, ReturnInst *RI,
 /// Returns true if the platform/triple supports the stackprotectorcreate pseudo
 /// node.
 static bool CreatePrologue(Function *F, Module *M, ReturnInst *RI,
-                           const TargetLoweringBase *TLI, const Triple &TT,
-                           AllocaInst *&AI, Value *&StackGuardVar) {
+                           const TargetLoweringBase *TLI, AllocaInst *&AI,
+                           Value *&StackGuardVar) {
   bool SupportsSelectionDAGSP = false;
-  PointerType *PtrTy = Type::getInt8PtrTy(RI->getContext());
   IRBuilder<> B(&F->getEntryBlock().front());
 
-  StackGuardVar = TLI->getStackCookieLocation(B);
+  StackGuardVar = TLI->getIRStackGuard(B);
   if (!StackGuardVar) {
-    if (TT.isOSOpenBSD()) {
-      StackGuardVar = M->getOrInsertGlobal("__guard_local", PtrTy);
-      cast<GlobalValue>(StackGuardVar)
-          ->setVisibility(GlobalValue::HiddenVisibility);
-    } else {
-      SupportsSelectionDAGSP = true;
-      StackGuardVar = M->getOrInsertGlobal("__stack_chk_guard", PtrTy);
-    }
+    /// Use SelectionDAG SSP handling, since there isn't an IR guard.
+    SupportsSelectionDAGSP = true;
+    TLI->insertSSPDeclarations(*M);
+    StackGuardVar = TLI->getSDStackGuard(*M);
   }
+  assert(StackGuardVar && "Must have stack guard available");
 
+  PointerType *PtrTy = Type::getInt8PtrTy(RI->getContext());
   AI = B.CreateAlloca(PtrTy, nullptr, "StackGuardSlot");
   LoadInst *LI = B.CreateLoad(StackGuardVar, "StackGuard");
   B.CreateCall(Intrinsic::getDeclaration(M, Intrinsic::stackprotector),
                {LI, AI});
-
   return SupportsSelectionDAGSP;
 }
 
@@ -362,7 +308,6 @@ static bool CreatePrologue(Function *F, Module *M, ReturnInst *RI,
 ///  - The epilogue checks the value stored in the prologue against the original
 ///    value. It calls __stack_chk_fail if they differ.
 bool StackProtector::InsertStackProtectors() {
-  bool HasPrologue = false;
   bool SupportsSelectionDAGSP =
       EnableSelectionDAGSP && !TM->Options.EnableFastISel;
   AllocaInst *AI = nullptr;       // Place on stack that stores the stack guard.
@@ -377,27 +322,10 @@ bool StackProtector::InsertStackProtectors() {
     if (!HasPrologue) {
       HasPrologue = true;
       SupportsSelectionDAGSP &=
-          CreatePrologue(F, M, RI, TLI, Trip, AI, StackGuardVar);
+          CreatePrologue(F, M, RI, TLI, AI, StackGuardVar);
     }
 
-    if (SupportsSelectionDAGSP) {
-      // Since we have a potential tail call, insert the special stack check
-      // intrinsic.
-      Instruction *InsertionPt = nullptr;
-      if (CallInst *CI = FindPotentialTailCall(BB, RI, TLI)) {
-        InsertionPt = CI;
-      } else {
-        InsertionPt = RI;
-        // At this point we know that BB has a return statement so it *DOES*
-        // have a terminator.
-        assert(InsertionPt != nullptr &&
-               "BB must have a terminator instruction at this point.");
-      }
-
-      Function *Intrinsic =
-          Intrinsic::getDeclaration(M, Intrinsic::stackprotectorcheck);
-      CallInst::Create(Intrinsic, StackGuardVar, "", InsertionPt);
-    } else {
+    if (!SupportsSelectionDAGSP) {
       // If we do not support SelectionDAG based tail calls, generate IR level
       // tail calls.
       //
@@ -428,6 +356,10 @@ bool StackProtector::InsertStackProtectors() {
       // fail BB generated by the stack protector pseudo instruction.
       BasicBlock *FailBB = CreateFailBB();
 
+      // Set HasIRCheck to true, so that SelectionDAG will not generate its own
+      // version.
+      HasIRCheck = true;
+
       // Split the basic block before the return instruction.
       BasicBlock *NewBB = BB->splitBasicBlock(RI->getIterator(), "SP_return");
 
@@ -487,3 +419,7 @@ BasicBlock *StackProtector::CreateFailBB() {
   B.CreateUnreachable();
   return FailBB;
 }
+
+bool StackProtector::shouldEmitSDCheck(const BasicBlock &BB) const {
+  return HasPrologue && !HasIRCheck && dyn_cast<ReturnInst>(BB.getTerminator());
+}
diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 7ec7006478a..8cadbb2dcd0 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -1746,3 +1746,32 @@ bool TargetLoweringBase::isLegalAddressingMode(const DataLayout &DL,
 
   return true;
 }
+
+//===----------------------------------------------------------------------===//
+//  Stack Protector
+//===----------------------------------------------------------------------===//
+
+// For OpenBSD return its special guard variable. Otherwise return nullptr,
+// so that SelectionDAG handle SSP.
+Value *TargetLoweringBase::getIRStackGuard(IRBuilder<> &IRB) const {
+  if (getTargetMachine().getTargetTriple().isOSOpenBSD()) {
+    Module &M = *IRB.GetInsertBlock()->getParent()->getParent();
+    PointerType *PtrTy = Type::getInt8PtrTy(M.getContext());
+    auto Guard = cast<GlobalValue>(M.getOrInsertGlobal("__guard_local", PtrTy));
+    Guard->setVisibility(GlobalValue::HiddenVisibility);
+    return Guard;
+  }
+  return nullptr;
+}
+
+// Currently only support "standard" __stack_chk_guard.
+// TODO: add LOAD_STACK_GUARD support.
+void TargetLoweringBase::insertSSPDeclarations(Module &M) const {
+  M.getOrInsertGlobal("__stack_chk_guard", Type::getInt8PtrTy(M.getContext()));
+}
+
+// Currently only support "standard" __stack_chk_guard.
+// TODO: add LOAD_STACK_GUARD support.
+Value *TargetLoweringBase::getSDStackGuard(const Module &M) const {
+  return M.getGlobalVariable("__stack_chk_guard");
+}