MS ABI: Use musttail for vtable thunks that pass arguments by value
This moves some memptr specific code into the generic thunk emission
codepath.
Fixes PR20053.
Reviewers: majnemer
Differential Revision: http://reviews.llvm.org/D4613
llvm-svn: 214004
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 17c3354..c13f181 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2045,19 +2045,8 @@
return args.add(RValue::get(Builder.CreateLoad(local)), type);
}
- if (isInAllocaArgument(CGM.getCXXABI(), type)) {
- AggValueSlot Slot = createPlaceholderSlot(*this, type);
- Slot.setExternallyDestructed();
-
- // FIXME: Either emit a copy constructor call, or figure out how to do
- // guaranteed tail calls with perfect forwarding in LLVM.
- CGM.ErrorUnsupported(param, "non-trivial argument copy for thunk");
- EmitNullInitialization(Slot.getAddr(), type);
-
- RValue RV = Slot.asRValue();
- args.add(RV, type);
- return;
- }
+ assert(!isInAllocaArgument(CGM.getCXXABI(), type) &&
+ "cannot emit delegate call arguments for inalloca arguments!");
args.add(convertTempToRValue(local, type, loc), type);
}
diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index ab806cc..b95e8f0 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -236,6 +236,18 @@
*this, LoadCXXThis(), Thunk->This)
: LoadCXXThis();
+ if (CurFnInfo->usesInAlloca()) {
+ // We don't handle return adjusting thunks, because they require us to call
+ // the copy constructor. For now, fall through and pretend the return
+ // adjustment was empty so we don't crash.
+ if (Thunk && !Thunk->Return.isEmpty()) {
+ CGM.ErrorUnsupported(
+ MD, "non-trivial argument copy for return-adjusting thunk");
+ }
+ EmitMustTailThunk(MD, AdjustedThisPtr, Callee);
+ return;
+ }
+
// Start building CallArgs.
CallArgList CallArgs;
QualType ThisType = MD->getThisType(getContext());
@@ -278,8 +290,9 @@
Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified());
// Now emit our call.
- RValue RV = EmitCall(*CurFnInfo, Callee, Slot, CallArgs, MD);
-
+ llvm::Instruction *CallOrInvoke;
+ RValue RV = EmitCall(*CurFnInfo, Callee, Slot, CallArgs, MD, &CallOrInvoke);
+
// Consider return adjustment if we have ThunkInfo.
if (Thunk && !Thunk->Return.isEmpty())
RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk);
@@ -294,6 +307,62 @@
FinishFunction();
}
+void CodeGenFunction::EmitMustTailThunk(const CXXMethodDecl *MD,
+ llvm::Value *AdjustedThisPtr,
+ llvm::Value *Callee) {
+ // Emitting a musttail call thunk doesn't use any of the CGCall.cpp machinery
+ // to translate AST arguments into LLVM IR arguments. For thunks, we know
+ // that the caller prototype more or less matches the callee prototype with
+ // the exception of 'this'.
+ SmallVector<llvm::Value *, 8> Args;
+ for (llvm::Argument &A : CurFn->args())
+ Args.push_back(&A);
+
+ // Set the adjusted 'this' pointer.
+ const ABIArgInfo &ThisAI = CurFnInfo->arg_begin()->info;
+ if (ThisAI.isDirect()) {
+ const ABIArgInfo &RetAI = CurFnInfo->getReturnInfo();
+ int ThisArgNo = RetAI.isIndirect() && !RetAI.isSRetAfterThis() ? 1 : 0;
+ llvm::Type *ThisType = Args[ThisArgNo]->getType();
+ if (ThisType != AdjustedThisPtr->getType())
+ AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
+ Args[ThisArgNo] = AdjustedThisPtr;
+ } else {
+ assert(ThisAI.isInAlloca() && "this is passed directly or inalloca");
+ llvm::Value *ThisAddr = GetAddrOfLocalVar(CXXABIThisDecl);
+ llvm::Type *ThisType =
+ cast<llvm::PointerType>(ThisAddr->getType())->getElementType();
+ if (ThisType != AdjustedThisPtr->getType())
+ AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
+ Builder.CreateStore(AdjustedThisPtr, ThisAddr);
+ }
+
+ // Emit the musttail call manually. Even if the prologue pushed cleanups, we
+ // don't actually want to run them.
+ llvm::CallInst *Call = Builder.CreateCall(Callee, Args);
+ Call->setTailCallKind(llvm::CallInst::TCK_MustTail);
+
+ // Apply the standard set of call attributes.
+ unsigned CallingConv;
+ CodeGen::AttributeListType AttributeList;
+ CGM.ConstructAttributeList(*CurFnInfo, MD, AttributeList, CallingConv,
+ /*AttrOnCallSite=*/true);
+ llvm::AttributeSet Attrs =
+ llvm::AttributeSet::get(getLLVMContext(), AttributeList);
+ Call->setAttributes(Attrs);
+ Call->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));
+
+ if (Call->getType()->isVoidTy())
+ Builder.CreateRetVoid();
+ else
+ Builder.CreateRet(Call);
+
+ // Finish the function to maintain CodeGenFunction invariants.
+ // FIXME: Don't emit unreachable code.
+ EmitBlock(createBasicBlock());
+ FinishFunction();
+}
+
void CodeGenFunction::GenerateThunk(llvm::Function *Fn,
const CGFunctionInfo &FnInfo,
GlobalDecl GD, const ThunkInfo &Thunk) {
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 8dea7bd..b612415 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -1210,6 +1210,10 @@
void EmitCallAndReturnForThunk(llvm::Value *Callee, const ThunkInfo *Thunk);
+ /// Emit a musttail call for a thunk with a potentially adjusted this pointer.
+ void EmitMustTailThunk(const CXXMethodDecl *MD, llvm::Value *AdjustedThisPtr,
+ llvm::Value *Callee);
+
/// GenerateThunk - Generate a thunk for the given method.
void GenerateThunk(llvm::Function *Fn, const CGFunctionInfo &FnInfo,
GlobalDecl GD, const ThunkInfo &Thunk);
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 0ab0940..23f9768 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1467,31 +1467,7 @@
CGF.Builder.CreateConstInBoundsGEP1_64(VTable, ML.Index, "vfn");
llvm::Value *Callee = CGF.Builder.CreateLoad(VFuncPtr);
- unsigned CallingConv;
- CodeGen::AttributeListType AttributeList;
- CGM.ConstructAttributeList(FnInfo, MD, AttributeList, CallingConv, true);
- llvm::AttributeSet Attrs =
- llvm::AttributeSet::get(CGF.getLLVMContext(), AttributeList);
-
- // Do a musttail call with perfect argument forwarding. Any inalloca argument
- // will be forwarded in place without any copy.
- SmallVector<llvm::Value *, 8> Args;
- for (llvm::Argument &A : ThunkFn->args())
- Args.push_back(&A);
- llvm::CallInst *Call = CGF.Builder.CreateCall(Callee, Args);
- Call->setTailCallKind(llvm::CallInst::TCK_MustTail);
- Call->setAttributes(Attrs);
- Call->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));
-
- if (Call->getType()->isVoidTy())
- CGF.Builder.CreateRetVoid();
- else
- CGF.Builder.CreateRet(Call);
-
- // Finish the function to maintain CodeGenFunction invariants.
- // FIXME: Don't emit unreachable code.
- CGF.EmitBlock(CGF.createBasicBlock());
- CGF.FinishFunction();
+ CGF.EmitCallAndReturnForThunk(Callee, 0);
return ThunkFn;
}