Fix Calling Convention through aliases

[erichkeane]

Summary

r369697 changed the behavior of stripPointerCasts to no longer include
aliases. However, the code in CGDeclCXX.cpp's createAtExitStub counted
on the looking through aliases to properly set the calling convention of
a call.

The result of the change was that the calling convention mismatch of the
call would be replaced with a llvm.trap, causing a runtime crash.

[pcc]

LGTM

clang/lib/CodeGen/CGDeclCXX.cpp

251 ↗

(On Diff #223617)

Nit: while here you could change this to auto *.

[rnk]

lgtm

cfe/trunk/lib/CodeGen/CGDeclCXX.cpp

llvm::Function *CodeGenFunction::createAtExitStub(const VarDecl &VD,
   CodeGenFunction CGF(CGM);
 
   CGF.StartFunction(GlobalDecl(&VD, DynamicInitKind::AtExit),
                     CGM.getContext().VoidTy, fn, FI, FunctionArgList());
 
   llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
 
  // Make sure the call and the callee agree on calling convention.
-  if (llvm::Function *dtorFn =
-          dyn_cast<llvm::Function>(dtor.getCallee()->stripPointerCasts()))
+  if (auto *dtorFn = dyn_cast<llvm::Function>(
+          dtor.getCallee()->stripPointerCastsAndAliases()))
     call->setCallingConv(dtorFn->getCallingConv());
 
   CGF.FinishFunction();
 
   return fn;
 }
 
 /// Register a global destructor using the C atexit runtime function.

cfe/trunk/test/CodeGenCXX/call-conv-thru-alias.cpp

+// RUN: %clang_cc1 -triple i686-windows-pc -emit-llvm -o - -mconstructor-aliases -O1 -disable-llvm-passes %s | FileCheck %s
+
+struct Base { virtual ~Base(); };
+struct Derived : Base {
+  virtual ~Derived();
+  static Derived inst;
+};
+
+Base::~Base(){}
+Derived::~Derived(){}
+Derived Derived::inst;
+
+// CHECK: @"??1Derived@@UAE@XZ" = dso_local unnamed_addr alias void (%struct.Derived*), bitcast (void (%struct.Base*)* @"??1Base@@UAE@XZ" to void (%struct.Derived*)*)
+
+// CHECK: define dso_local x86_thiscallcc void @"??1Base@@UAE@XZ"
+// CHECK: define internal void @"??__E?inst@Derived@@2U1@A@@YAXXZ"
+// CHECK: call i32 @atexit(void ()* @"??__F?inst@Derived@@2U1@A@@YAXXZ"
+//
+// CHECK: define internal void @"??__F?inst@Derived@@2U1@A@@YAXXZ"
+// CHECK-NEXT: entry:
+// CHECK-NEXT: call x86_thiscallcc void @"??1Derived@@UAE@XZ"

llvm/trunk/include/llvm/IR/Value.h

#include "llvm/IR/Value.def"
   /// Returns the original uncasted value.  If this is called on a non-pointer
   /// value, it returns 'this'.
   const Value *stripPointerCasts() const;
   Value *stripPointerCasts() {
     return const_cast<Value *>(
         static_cast<const Value *>(this)->stripPointerCasts());
   }
 
+  /// Strip off pointer casts, all-zero GEPs, address space casts, and aliases.
+  ///
+  /// Returns the original uncasted value.  If this is called on a non-pointer
+  /// value, it returns 'this'.
+  const Value *stripPointerCastsAndAliases() const;
+  Value *stripPointerCastsAndAliases() {
+    return const_cast<Value *>(
+        static_cast<const Value *>(this)->stripPointerCastsAndAliases());
+  }
+
   /// Strip off pointer casts, all-zero GEPs and address space casts
   /// but ensures the representation of the result stays the same.
   ///
   /// Returns the original uncasted value with the same representation. If this
   /// is called on a non-pointer value, it returns 'this'.
   const Value *stripPointerCastsSameRepresentation() const;
   Value *stripPointerCastsSameRepresentation() {
     return const_cast<Value *>(static_cast<const Value *>(this)

llvm/trunk/lib/IR/Value.cpp

replaceUsesWithIf(New, [BB](Use &U) {
     return !I || I->getParent() != BB;
   });
 }
 
 namespace {
 // Various metrics for how much to strip off of pointers.
 enum PointerStripKind {
   PSK_ZeroIndices,
+  PSK_ZeroIndicesAndAliases,
   PSK_ZeroIndicesSameRepresentation,
   PSK_ZeroIndicesAndInvariantGroups,
   PSK_InBoundsConstantIndices,
   PSK_InBounds
 };
 
 template <PointerStripKind StripKind>
 static const Value *stripPointerCastsAndOffsets(const Value *V) {
   if (!V->getType()->isPointerTy())
     return V;
 
   // Even though we don't look through PHI nodes, we could be called on an
   // instruction in an unreachable block, which may be on a cycle.
   SmallPtrSet<const Value *, 4> Visited;
 
   Visited.insert(V);
   do {
     if (auto *GEP = dyn_cast<GEPOperator>(V)) {
       switch (StripKind) {
       case PSK_ZeroIndices:
+      case PSK_ZeroIndicesAndAliases:
       case PSK_ZeroIndicesSameRepresentation:
       case PSK_ZeroIndicesAndInvariantGroups:
         if (!GEP->hasAllZeroIndices())
           return V;
         break;
       case PSK_InBoundsConstantIndices:
         if (!GEP->hasAllConstantIndices())
           return V;
         LLVM_FALLTHROUGH;
       case PSK_InBounds:
         if (!GEP->isInBounds())
           return V;
         break;
       }
       V = GEP->getPointerOperand();
     } else if (Operator::getOpcode(V) == Instruction::BitCast) {
       V = cast<Operator>(V)->getOperand(0);
     } else if (StripKind != PSK_ZeroIndicesSameRepresentation &&
                Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
       // TODO: If we know an address space cast will not change the
       //       representation we could look through it here as well.
       V = cast<Operator>(V)->getOperand(0);
+    } else if (StripKind == PSK_ZeroIndicesAndAliases && isa<GlobalAlias>(V)) {
+      V = cast<GlobalAlias>(V)->getAliasee();
     } else {
       if (const auto *Call = dyn_cast<CallBase>(V)) {
         if (const Value *RV = Call->getReturnedArgOperand()) {
           V = RV;
           continue;
         }
         // The result of launder.invariant.group must alias it's argument,
         // but it can't be marked with returned attribute, that's why it needs
static const Value *stripPointerCastsAndOffsets(const Value *V) {
   return V;
 }
 } // end anonymous namespace
 
 const Value *Value::stripPointerCasts() const {
   return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
 }
 
+const Value *Value::stripPointerCastsAndAliases() const {
+  return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
+}
+
 const Value *Value::stripPointerCastsSameRepresentation() const {
   return stripPointerCastsAndOffsets<PSK_ZeroIndicesSameRepresentation>(this);
 }
 
 const Value *Value::stripInBoundsConstantOffsets() const {
   return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
 }