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llvm-project/clang/lib/CodeGen/ItaniumCXXABI.cpp

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//===------- ItaniumCXXABI.cpp - Emit LLVM Code from ASTs for a Module ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This provides C++ code generation targeting the Itanium C++ ABI. The class
// in this file generates structures that follow the Itanium C++ ABI, which is
// documented at:
// http://www.codesourcery.com/public/cxx-abi/abi.html
// http://www.codesourcery.com/public/cxx-abi/abi-eh.html
//
// It also supports the closely-related ARM ABI, documented at:
// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
//
//===----------------------------------------------------------------------===//
#include "CGCXXABI.h"
#include "CGRecordLayout.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include <clang/AST/Mangle.h>
#include <clang/AST/Type.h>
#include <llvm/Target/TargetData.h>
#include <llvm/Value.h>
using namespace clang;
using namespace CodeGen;
namespace {
class ItaniumCXXABI : public CodeGen::CGCXXABI {
private:
const llvm::IntegerType *PtrDiffTy;
protected:
bool IsARM;
// It's a little silly for us to cache this.
const llvm::IntegerType *getPtrDiffTy() {
if (!PtrDiffTy) {
QualType T = getContext().getPointerDiffType();
const llvm::Type *Ty = CGM.getTypes().ConvertTypeRecursive(T);
PtrDiffTy = cast<llvm::IntegerType>(Ty);
}
return PtrDiffTy;
}
bool NeedsArrayCookie(const CXXNewExpr *expr);
bool NeedsArrayCookie(const CXXDeleteExpr *expr,
QualType elementType);
public:
ItaniumCXXABI(CodeGen::CodeGenModule &CGM, bool IsARM = false) :
CGCXXABI(CGM), PtrDiffTy(0), IsARM(IsARM) { }
bool isZeroInitializable(const MemberPointerType *MPT);
const llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT);
llvm::Value *EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
llvm::Value *&This,
llvm::Value *MemFnPtr,
const MemberPointerType *MPT);
llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
llvm::Value *Base,
llvm::Value *MemPtr,
const MemberPointerType *MPT);
llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
const CastExpr *E,
llvm::Value *Src);
llvm::Constant *EmitMemberPointerConversion(llvm::Constant *C,
const CastExpr *E);
llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
CharUnits offset);
llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
llvm::Value *L,
llvm::Value *R,
const MemberPointerType *MPT,
bool Inequality);
llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
llvm::Value *Addr,
const MemberPointerType *MPT);
void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
CXXCtorType T,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys);
void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
CXXDtorType T,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys);
void BuildInstanceFunctionParams(CodeGenFunction &CGF,
QualType &ResTy,
FunctionArgList &Params);
void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
llvm::Value *NewPtr,
llvm::Value *NumElements,
const CXXNewExpr *expr,
QualType ElementType);
void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
const CXXDeleteExpr *expr,
QualType ElementType, llvm::Value *&NumElements,
llvm::Value *&AllocPtr, CharUnits &CookieSize);
void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
llvm::GlobalVariable *DeclPtr);
};
class ARMCXXABI : public ItaniumCXXABI {
public:
ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM, /*ARM*/ true) {}
void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
CXXCtorType T,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys);
void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
CXXDtorType T,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys);
void BuildInstanceFunctionParams(CodeGenFunction &CGF,
QualType &ResTy,
FunctionArgList &Params);
void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy);
CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
llvm::Value *NewPtr,
llvm::Value *NumElements,
const CXXNewExpr *expr,
QualType ElementType);
void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
const CXXDeleteExpr *expr,
QualType ElementType, llvm::Value *&NumElements,
llvm::Value *&AllocPtr, CharUnits &CookieSize);
private:
/// \brief Returns true if the given instance method is one of the
/// kinds that the ARM ABI says returns 'this'.
static bool HasThisReturn(GlobalDecl GD) {
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
return ((isa<CXXDestructorDecl>(MD) && GD.getDtorType() != Dtor_Deleting) ||
(isa<CXXConstructorDecl>(MD)));
}
};
}
CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
return new ItaniumCXXABI(CGM);
}
CodeGen::CGCXXABI *CodeGen::CreateARMCXXABI(CodeGenModule &CGM) {
return new ARMCXXABI(CGM);
}
const llvm::Type *
ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
if (MPT->isMemberDataPointer())
return getPtrDiffTy();
else
return llvm::StructType::get(CGM.getLLVMContext(),
getPtrDiffTy(), getPtrDiffTy(), NULL);
}
/// In the Itanium and ARM ABIs, method pointers have the form:
/// struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
///
/// In the Itanium ABI:
/// - method pointers are virtual if (memptr.ptr & 1) is nonzero
/// - the this-adjustment is (memptr.adj)
/// - the virtual offset is (memptr.ptr - 1)
///
/// In the ARM ABI:
/// - method pointers are virtual if (memptr.adj & 1) is nonzero
/// - the this-adjustment is (memptr.adj >> 1)
/// - the virtual offset is (memptr.ptr)
/// ARM uses 'adj' for the virtual flag because Thumb functions
/// may be only single-byte aligned.
///
/// If the member is virtual, the adjusted 'this' pointer points
/// to a vtable pointer from which the virtual offset is applied.
///
/// If the member is non-virtual, memptr.ptr is the address of
/// the function to call.
llvm::Value *
ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
llvm::Value *&This,
llvm::Value *MemFnPtr,
const MemberPointerType *MPT) {
CGBuilderTy &Builder = CGF.Builder;
const FunctionProtoType *FPT =
MPT->getPointeeType()->getAs<FunctionProtoType>();
const CXXRecordDecl *RD =
cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
const llvm::FunctionType *FTy =
CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(RD, FPT),
FPT->isVariadic());
const llvm::IntegerType *ptrdiff = getPtrDiffTy();
llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(ptrdiff, 1);
llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
// Extract memptr.adj, which is in the second field.
llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
// Compute the true adjustment.
llvm::Value *Adj = RawAdj;
if (IsARM)
Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
// Apply the adjustment and cast back to the original struct type
// for consistency.
llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
// Load the function pointer.
llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
// If the LSB in the function pointer is 1, the function pointer points to
// a virtual function.
llvm::Value *IsVirtual;
if (IsARM)
IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
else
IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
// In the virtual path, the adjustment left 'This' pointing to the
// vtable of the correct base subobject. The "function pointer" is an
// offset within the vtable (+1 for the virtual flag on non-ARM).
CGF.EmitBlock(FnVirtual);
// Cast the adjusted this to a pointer to vtable pointer and load.
const llvm::Type *VTableTy = Builder.getInt8PtrTy();
llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
VTable = Builder.CreateLoad(VTable, "memptr.vtable");
// Apply the offset.
llvm::Value *VTableOffset = FnAsInt;
if (!IsARM) VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
VTable = Builder.CreateGEP(VTable, VTableOffset);
// Load the virtual function to call.
VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn");
CGF.EmitBranch(FnEnd);
// In the non-virtual path, the function pointer is actually a
// function pointer.
CGF.EmitBlock(FnNonVirtual);
llvm::Value *NonVirtualFn =
Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
// We're done.
CGF.EmitBlock(FnEnd);
llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2);
Callee->addIncoming(VirtualFn, FnVirtual);
Callee->addIncoming(NonVirtualFn, FnNonVirtual);
return Callee;
}
/// Compute an l-value by applying the given pointer-to-member to a
/// base object.
llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
llvm::Value *Base,
llvm::Value *MemPtr,
const MemberPointerType *MPT) {
assert(MemPtr->getType() == getPtrDiffTy());
CGBuilderTy &Builder = CGF.Builder;
unsigned AS = cast<llvm::PointerType>(Base->getType())->getAddressSpace();
// Cast to char*.
Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
// Apply the offset, which we assume is non-null.
llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
// Cast the address to the appropriate pointer type, adopting the
// address space of the base pointer.
const llvm::Type *PType
= CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
return Builder.CreateBitCast(Addr, PType);
}
/// Perform a derived-to-base or base-to-derived member pointer conversion.
///
/// Obligatory offset/adjustment diagram:
/// <-- offset --> <-- adjustment -->
/// |--------------------------|----------------------|--------------------|
/// ^Derived address point ^Base address point ^Member address point
///
/// So when converting a base member pointer to a derived member pointer,
/// we add the offset to the adjustment because the address point has
/// decreased; and conversely, when converting a derived MP to a base MP
/// we subtract the offset from the adjustment because the address point
/// has increased.
///
/// The standard forbids (at compile time) conversion to and from
/// virtual bases, which is why we don't have to consider them here.
///
/// The standard forbids (at run time) casting a derived MP to a base
/// MP when the derived MP does not point to a member of the base.
/// This is why -1 is a reasonable choice for null data member
/// pointers.
llvm::Value *
ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
const CastExpr *E,
llvm::Value *Src) {
assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
E->getCastKind() == CK_BaseToDerivedMemberPointer);
if (isa<llvm::Constant>(Src))
return EmitMemberPointerConversion(cast<llvm::Constant>(Src), E);
CGBuilderTy &Builder = CGF.Builder;
const MemberPointerType *SrcTy =
E->getSubExpr()->getType()->getAs<MemberPointerType>();
const MemberPointerType *DestTy = E->getType()->getAs<MemberPointerType>();
const CXXRecordDecl *SrcDecl = SrcTy->getClass()->getAsCXXRecordDecl();
const CXXRecordDecl *DestDecl = DestTy->getClass()->getAsCXXRecordDecl();
bool DerivedToBase =
E->getCastKind() == CK_DerivedToBaseMemberPointer;
const CXXRecordDecl *DerivedDecl;
if (DerivedToBase)
DerivedDecl = SrcDecl;
else
DerivedDecl = DestDecl;
llvm::Constant *Adj =
CGF.CGM.GetNonVirtualBaseClassOffset(DerivedDecl,
E->path_begin(),
E->path_end());
if (!Adj) return Src;
// For member data pointers, this is just a matter of adding the
// offset if the source is non-null.
if (SrcTy->isMemberDataPointer()) {
llvm::Value *Dst;
if (DerivedToBase)
Dst = Builder.CreateNSWSub(Src, Adj, "adj");
else
Dst = Builder.CreateNSWAdd(Src, Adj, "adj");
// Null check.
llvm::Value *Null = llvm::Constant::getAllOnesValue(Src->getType());
llvm::Value *IsNull = Builder.CreateICmpEQ(Src, Null, "memptr.isnull");
return Builder.CreateSelect(IsNull, Src, Dst);
}
// The this-adjustment is left-shifted by 1 on ARM.
if (IsARM) {
uint64_t Offset = cast<llvm::ConstantInt>(Adj)->getZExtValue();
Offset <<= 1;
Adj = llvm::ConstantInt::get(Adj->getType(), Offset);
}
llvm::Value *SrcAdj = Builder.CreateExtractValue(Src, 1, "src.adj");
llvm::Value *DstAdj;
if (DerivedToBase)
DstAdj = Builder.CreateNSWSub(SrcAdj, Adj, "adj");
else
DstAdj = Builder.CreateNSWAdd(SrcAdj, Adj, "adj");
return Builder.CreateInsertValue(Src, DstAdj, 1);
}
llvm::Constant *
ItaniumCXXABI::EmitMemberPointerConversion(llvm::Constant *C,
const CastExpr *E) {
const MemberPointerType *SrcTy =
E->getSubExpr()->getType()->getAs<MemberPointerType>();
const MemberPointerType *DestTy =
E->getType()->getAs<MemberPointerType>();
bool DerivedToBase =
E->getCastKind() == CK_DerivedToBaseMemberPointer;
const CXXRecordDecl *DerivedDecl;
if (DerivedToBase)
DerivedDecl = SrcTy->getClass()->getAsCXXRecordDecl();
else
DerivedDecl = DestTy->getClass()->getAsCXXRecordDecl();
// Calculate the offset to the base class.
llvm::Constant *Offset =
CGM.GetNonVirtualBaseClassOffset(DerivedDecl,
E->path_begin(),
E->path_end());
// If there's no offset, we're done.
if (!Offset) return C;
// If the source is a member data pointer, we have to do a null
// check and then add the offset. In the common case, we can fold
// away the offset.
if (SrcTy->isMemberDataPointer()) {
assert(C->getType() == getPtrDiffTy());
// If it's a constant int, just create a new constant int.
if (llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C)) {
int64_t Src = CI->getSExtValue();
// Null converts to null.
if (Src == -1) return CI;
// Otherwise, just add the offset.
int64_t OffsetV = cast<llvm::ConstantInt>(Offset)->getSExtValue();
int64_t Dst = (DerivedToBase ? Src - OffsetV : Src + OffsetV);
return llvm::ConstantInt::get(CI->getType(), Dst, /*signed*/ true);
}
// Otherwise, we have to form a constant select expression.
llvm::Constant *Null = llvm::Constant::getAllOnesValue(C->getType());
llvm::Constant *IsNull =
llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, C, Null);
llvm::Constant *Dst;
if (DerivedToBase)
Dst = llvm::ConstantExpr::getNSWSub(C, Offset);
else
Dst = llvm::ConstantExpr::getNSWAdd(C, Offset);
return llvm::ConstantExpr::getSelect(IsNull, Null, Dst);
}
// The this-adjustment is left-shifted by 1 on ARM.
if (IsARM) {
int64_t OffsetV = cast<llvm::ConstantInt>(Offset)->getSExtValue();
OffsetV <<= 1;
Offset = llvm::ConstantInt::get(Offset->getType(), OffsetV);
}
llvm::ConstantStruct *CS = cast<llvm::ConstantStruct>(C);
llvm::Constant *Values[2] = { CS->getOperand(0), 0 };
if (DerivedToBase)
Values[1] = llvm::ConstantExpr::getSub(CS->getOperand(1), Offset);
else
Values[1] = llvm::ConstantExpr::getAdd(CS->getOperand(1), Offset);
return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2,
/*Packed=*/false);
}
llvm::Constant *
ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
const llvm::Type *ptrdiff_t = getPtrDiffTy();
// Itanium C++ ABI 2.3:
// A NULL pointer is represented as -1.
if (MPT->isMemberDataPointer())
return llvm::ConstantInt::get(ptrdiff_t, -1ULL, /*isSigned=*/true);
llvm::Constant *Zero = llvm::ConstantInt::get(ptrdiff_t, 0);
llvm::Constant *Values[2] = { Zero, Zero };
return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2,
/*Packed=*/false);
}
llvm::Constant *
ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
CharUnits offset) {
// Itanium C++ ABI 2.3:
// A pointer to data member is an offset from the base address of
// the class object containing it, represented as a ptrdiff_t
return llvm::ConstantInt::get(getPtrDiffTy(), offset.getQuantity());
}
llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) {
assert(MD->isInstance() && "Member function must not be static!");
MD = MD->getCanonicalDecl();
CodeGenTypes &Types = CGM.getTypes();
const llvm::Type *ptrdiff_t = getPtrDiffTy();
// Get the function pointer (or index if this is a virtual function).
llvm::Constant *MemPtr[2];
if (MD->isVirtual()) {
uint64_t Index = CGM.getVTables().getMethodVTableIndex(MD);
const ASTContext &Context = getContext();
CharUnits PointerWidth =
Context.toCharUnitsFromBits(Context.Target.getPointerWidth(0));
uint64_t VTableOffset = (Index * PointerWidth.getQuantity());
if (IsARM) {
// ARM C++ ABI 3.2.1:
// This ABI specifies that adj contains twice the this
// adjustment, plus 1 if the member function is virtual. The
// least significant bit of adj then makes exactly the same
// discrimination as the least significant bit of ptr does for
// Itanium.
MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset);
MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, 1);
} else {
// Itanium C++ ABI 2.3:
// For a virtual function, [the pointer field] is 1 plus the
// virtual table offset (in bytes) of the function,
// represented as a ptrdiff_t.
MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset + 1);
MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, 0);
}
} else {
QualType fnType = MD->getType();
const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
const llvm::Type *Ty;
// Check whether the function has a computable LLVM signature.
if (!CodeGenTypes::VerifyFuncTypeComplete(FPT)) {
// The function has a computable LLVM signature; use the correct type.
Ty = Types.GetFunctionType(Types.getFunctionInfo(MD),
FPT->isVariadic());
} else {
// Use an arbitrary non-function type to tell GetAddrOfFunction that the
// function type is incomplete.
Ty = ptrdiff_t;
}
llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty);
MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, ptrdiff_t);
MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, 0);
}
return llvm::ConstantStruct::get(CGM.getLLVMContext(),
MemPtr, 2, /*Packed=*/false);
}
/// The comparison algorithm is pretty easy: the member pointers are
/// the same if they're either bitwise identical *or* both null.
///
/// ARM is different here only because null-ness is more complicated.
llvm::Value *
ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
llvm::Value *L,
llvm::Value *R,
const MemberPointerType *MPT,
bool Inequality) {
CGBuilderTy &Builder = CGF.Builder;
llvm::ICmpInst::Predicate Eq;
llvm::Instruction::BinaryOps And, Or;
if (Inequality) {
Eq = llvm::ICmpInst::ICMP_NE;
And = llvm::Instruction::Or;
Or = llvm::Instruction::And;
} else {
Eq = llvm::ICmpInst::ICMP_EQ;
And = llvm::Instruction::And;
Or = llvm::Instruction::Or;
}
// Member data pointers are easy because there's a unique null
// value, so it just comes down to bitwise equality.
if (MPT->isMemberDataPointer())
return Builder.CreateICmp(Eq, L, R);
// For member function pointers, the tautologies are more complex.
// The Itanium tautology is:
// (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj))
// The ARM tautology is:
// (L == R) <==> (L.ptr == R.ptr &&
// (L.adj == R.adj ||
// (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0)))
// The inequality tautologies have exactly the same structure, except
// applying De Morgan's laws.
llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr");
llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr");
// This condition tests whether L.ptr == R.ptr. This must always be
// true for equality to hold.
llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr");
// This condition, together with the assumption that L.ptr == R.ptr,
// tests whether the pointers are both null. ARM imposes an extra
// condition.
llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType());
llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null");
// This condition tests whether L.adj == R.adj. If this isn't
// true, the pointers are unequal unless they're both null.
llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj");
llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj");
llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj");
// Null member function pointers on ARM clear the low bit of Adj,
// so the zero condition has to check that neither low bit is set.
if (IsARM) {
llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1);
// Compute (l.adj | r.adj) & 1 and test it against zero.
llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj");
llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One);
llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero,
"cmp.or.adj");
EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero);
}
// Tie together all our conditions.
llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq);
Result = Builder.CreateBinOp(And, PtrEq, Result,
Inequality ? "memptr.ne" : "memptr.eq");
return Result;
}
llvm::Value *
ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
llvm::Value *MemPtr,
const MemberPointerType *MPT) {
CGBuilderTy &Builder = CGF.Builder;
/// For member data pointers, this is just a check against -1.
if (MPT->isMemberDataPointer()) {
assert(MemPtr->getType() == getPtrDiffTy());
llvm::Value *NegativeOne =
llvm::Constant::getAllOnesValue(MemPtr->getType());
return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool");
}
// In Itanium, a member function pointer is not null if 'ptr' is not null.
llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr");
llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0);
llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool");
// On ARM, a member function pointer is also non-null if the low bit of 'adj'
// (the virtual bit) is set.
if (IsARM) {
llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
"memptr.isvirtual");
Result = Builder.CreateOr(Result, IsVirtual);
}
return Result;
}
/// The Itanium ABI requires non-zero initialization only for data
/// member pointers, for which '0' is a valid offset.
bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
return MPT->getPointeeType()->isFunctionType();
}
/// The generic ABI passes 'this', plus a VTT if it's initializing a
/// base subobject.
void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
CXXCtorType Type,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys) {
ASTContext &Context = getContext();
// 'this' is already there.
// Check if we need to add a VTT parameter (which has type void **).
if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0)
ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
}
/// The ARM ABI does the same as the Itanium ABI, but returns 'this'.
void ARMCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
CXXCtorType Type,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys) {
ItaniumCXXABI::BuildConstructorSignature(Ctor, Type, ResTy, ArgTys);
ResTy = ArgTys[0];
}
/// The generic ABI passes 'this', plus a VTT if it's destroying a
/// base subobject.
void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
CXXDtorType Type,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys) {
ASTContext &Context = getContext();
// 'this' is already there.
// Check if we need to add a VTT parameter (which has type void **).
if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0)
ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
}
/// The ARM ABI does the same as the Itanium ABI, but returns 'this'
/// for non-deleting destructors.
void ARMCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
CXXDtorType Type,
CanQualType &ResTy,
llvm::SmallVectorImpl<CanQualType> &ArgTys) {
ItaniumCXXABI::BuildDestructorSignature(Dtor, Type, ResTy, ArgTys);
if (Type != Dtor_Deleting)
ResTy = ArgTys[0];
}
void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
QualType &ResTy,
FunctionArgList &Params) {
/// Create the 'this' variable.
BuildThisParam(CGF, Params);
const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
assert(MD->isInstance());
// Check if we need a VTT parameter as well.
if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) {
ASTContext &Context = getContext();
// FIXME: avoid the fake decl
QualType T = Context.getPointerType(Context.VoidPtrTy);
ImplicitParamDecl *VTTDecl
= ImplicitParamDecl::Create(Context, 0, MD->getLocation(),
&Context.Idents.get("vtt"), T);
Params.push_back(VTTDecl);
getVTTDecl(CGF) = VTTDecl;
}
}
void ARMCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
QualType &ResTy,
FunctionArgList &Params) {
ItaniumCXXABI::BuildInstanceFunctionParams(CGF, ResTy, Params);
// Return 'this' from certain constructors and destructors.
if (HasThisReturn(CGF.CurGD))
ResTy = Params[0]->getType();
}
void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
/// Initialize the 'this' slot.
EmitThisParam(CGF);
/// Initialize the 'vtt' slot if needed.
if (getVTTDecl(CGF)) {
getVTTValue(CGF)
= CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)),
"vtt");
}
}
void ARMCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
ItaniumCXXABI::EmitInstanceFunctionProlog(CGF);
/// Initialize the return slot to 'this' at the start of the
/// function.
if (HasThisReturn(CGF.CurGD))
CGF.Builder.CreateStore(CGF.LoadCXXThis(), CGF.ReturnValue);
}
void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
RValue RV, QualType ResultType) {
if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
// Destructor thunks in the ARM ABI have indeterminate results.
const llvm::Type *T =
cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType();
RValue Undef = RValue::get(llvm::UndefValue::get(T));
return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
}
/************************** Array allocation cookies **************************/
bool ItaniumCXXABI::NeedsArrayCookie(const CXXNewExpr *expr) {
// If the class's usual deallocation function takes two arguments,
// it needs a cookie.
if (expr->doesUsualArrayDeleteWantSize())
return true;
// Otherwise, if the class has a non-trivial destructor, it always
// needs a cookie.
const CXXRecordDecl *record =
expr->getAllocatedType()->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
return (record && !record->hasTrivialDestructor());
}
bool ItaniumCXXABI::NeedsArrayCookie(const CXXDeleteExpr *expr,
QualType elementType) {
// If the class's usual deallocation function takes two arguments,
// it needs a cookie.
if (expr->doesUsualArrayDeleteWantSize())
return true;
// Otherwise, if the class has a non-trivial destructor, it always
// needs a cookie.
const CXXRecordDecl *record =
elementType->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
return (record && !record->hasTrivialDestructor());
}
CharUnits ItaniumCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
if (!NeedsArrayCookie(expr))
return CharUnits::Zero();
// Padding is the maximum of sizeof(size_t) and alignof(elementType)
ASTContext &Ctx = getContext();
return std::max(Ctx.getTypeSizeInChars(Ctx.getSizeType()),
Ctx.getTypeAlignInChars(expr->getAllocatedType()));
}
llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
llvm::Value *NewPtr,
llvm::Value *NumElements,
const CXXNewExpr *expr,
QualType ElementType) {
assert(NeedsArrayCookie(expr));
unsigned AS = cast<llvm::PointerType>(NewPtr->getType())->getAddressSpace();
ASTContext &Ctx = getContext();
QualType SizeTy = Ctx.getSizeType();
CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy);
// The size of the cookie.
CharUnits CookieSize =
std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType));
// Compute an offset to the cookie.
llvm::Value *CookiePtr = NewPtr;
CharUnits CookieOffset = CookieSize - SizeSize;
if (!CookieOffset.isZero())
CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr,
CookieOffset.getQuantity());
// Write the number of elements into the appropriate slot.
llvm::Value *NumElementsPtr
= CGF.Builder.CreateBitCast(CookiePtr,
CGF.ConvertType(SizeTy)->getPointerTo(AS));
CGF.Builder.CreateStore(NumElements, NumElementsPtr);
// Finally, compute a pointer to the actual data buffer by skipping
// over the cookie completely.
return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
CookieSize.getQuantity());
}
void ItaniumCXXABI::ReadArrayCookie(CodeGenFunction &CGF,
llvm::Value *Ptr,
const CXXDeleteExpr *expr,
QualType ElementType,
llvm::Value *&NumElements,
llvm::Value *&AllocPtr,
CharUnits &CookieSize) {
// Derive a char* in the same address space as the pointer.
unsigned AS = cast<llvm::PointerType>(Ptr->getType())->getAddressSpace();
const llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS);
// If we don't need an array cookie, bail out early.
if (!NeedsArrayCookie(expr, ElementType)) {
AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
NumElements = 0;
CookieSize = CharUnits::Zero();
return;
}
QualType SizeTy = getContext().getSizeType();
CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy);
const llvm::Type *SizeLTy = CGF.ConvertType(SizeTy);
CookieSize
= std::max(SizeSize, getContext().getTypeAlignInChars(ElementType));
CharUnits NumElementsOffset = CookieSize - SizeSize;
// Compute the allocated pointer.
AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr,
-CookieSize.getQuantity());
llvm::Value *NumElementsPtr = AllocPtr;
if (!NumElementsOffset.isZero())
NumElementsPtr =
CGF.Builder.CreateConstInBoundsGEP1_64(NumElementsPtr,
NumElementsOffset.getQuantity());
NumElementsPtr =
CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS));
NumElements = CGF.Builder.CreateLoad(NumElementsPtr);
}
CharUnits ARMCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
if (!NeedsArrayCookie(expr))
return CharUnits::Zero();
// On ARM, the cookie is always:
// struct array_cookie {
// std::size_t element_size; // element_size != 0
// std::size_t element_count;
// };
// TODO: what should we do if the allocated type actually wants
// greater alignment?
return getContext().getTypeSizeInChars(getContext().getSizeType()) * 2;
}
llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
llvm::Value *NewPtr,
llvm::Value *NumElements,
const CXXNewExpr *expr,
QualType ElementType) {
assert(NeedsArrayCookie(expr));
// NewPtr is a char*.
unsigned AS = cast<llvm::PointerType>(NewPtr->getType())->getAddressSpace();
ASTContext &Ctx = getContext();
CharUnits SizeSize = Ctx.getTypeSizeInChars(Ctx.getSizeType());
const llvm::IntegerType *SizeTy =
cast<llvm::IntegerType>(CGF.ConvertType(Ctx.getSizeType()));
// The cookie is always at the start of the buffer.
llvm::Value *CookiePtr = NewPtr;
// The first element is the element size.
CookiePtr = CGF.Builder.CreateBitCast(CookiePtr, SizeTy->getPointerTo(AS));
llvm::Value *ElementSize = llvm::ConstantInt::get(SizeTy,
Ctx.getTypeSizeInChars(ElementType).getQuantity());
CGF.Builder.CreateStore(ElementSize, CookiePtr);
// The second element is the element count.
CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_32(CookiePtr, 1);
CGF.Builder.CreateStore(NumElements, CookiePtr);
// Finally, compute a pointer to the actual data buffer by skipping
// over the cookie completely.
CharUnits CookieSize = 2 * SizeSize;
return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
CookieSize.getQuantity());
}
void ARMCXXABI::ReadArrayCookie(CodeGenFunction &CGF,
llvm::Value *Ptr,
const CXXDeleteExpr *expr,
QualType ElementType,
llvm::Value *&NumElements,
llvm::Value *&AllocPtr,
CharUnits &CookieSize) {
// Derive a char* in the same address space as the pointer.
unsigned AS = cast<llvm::PointerType>(Ptr->getType())->getAddressSpace();
const llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS);
// If we don't need an array cookie, bail out early.
if (!NeedsArrayCookie(expr, ElementType)) {
AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
NumElements = 0;
CookieSize = CharUnits::Zero();
return;
}
QualType SizeTy = getContext().getSizeType();
CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy);
const llvm::Type *SizeLTy = CGF.ConvertType(SizeTy);
// The cookie size is always 2 * sizeof(size_t).
CookieSize = 2 * SizeSize;
// The allocated pointer is the input ptr, minus that amount.
AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy);
AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr,
-CookieSize.getQuantity());
// The number of elements is at offset sizeof(size_t) relative to that.
llvm::Value *NumElementsPtr
= CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr,
SizeSize.getQuantity());
NumElementsPtr =
CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS));
NumElements = CGF.Builder.CreateLoad(NumElementsPtr);
}
/*********************** Static local initialization **************************/
static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM,
const llvm::PointerType *GuardPtrTy) {
// int __cxa_guard_acquire(__guard *guard_object);
std::vector<const llvm::Type*> Args(1, GuardPtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
Args, /*isVarArg=*/false);
return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire");
}
static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM,
const llvm::PointerType *GuardPtrTy) {
// void __cxa_guard_release(__guard *guard_object);
std::vector<const llvm::Type*> Args(1, GuardPtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGM.getLLVMContext()),
Args, /*isVarArg=*/false);
return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release");
}
static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM,
const llvm::PointerType *GuardPtrTy) {
// void __cxa_guard_abort(__guard *guard_object);
std::vector<const llvm::Type*> Args(1, GuardPtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGM.getLLVMContext()),
Args, /*isVarArg=*/false);
return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort");
}
namespace {
struct CallGuardAbort : EHScopeStack::Cleanup {
llvm::GlobalVariable *Guard;
CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
void Emit(CodeGenFunction &CGF, bool IsForEH) {
CGF.Builder.CreateCall(getGuardAbortFn(CGF.CGM, Guard->getType()), Guard)
->setDoesNotThrow();
}
};
}
/// The ARM code here follows the Itanium code closely enough that we
/// just special-case it at particular places.
void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
const VarDecl &D,
llvm::GlobalVariable *GV) {
CGBuilderTy &Builder = CGF.Builder;
// We only need to use thread-safe statics for local variables;
// global initialization is always single-threaded.
bool ThreadsafeStatics = (getContext().getLangOptions().ThreadsafeStatics &&
D.isLocalVarDecl());
// Guard variables are 64 bits in the generic ABI and 32 bits on ARM.
const llvm::IntegerType *GuardTy
= (IsARM ? Builder.getInt32Ty() : Builder.getInt64Ty());
const llvm::PointerType *GuardPtrTy = GuardTy->getPointerTo();
// Create the guard variable.
llvm::SmallString<256> GuardVName;
llvm::raw_svector_ostream Out(GuardVName);
getMangleContext().mangleItaniumGuardVariable(&D, Out);
Out.flush();
// Just absorb linkage and visibility from the variable.
llvm::GlobalVariable *GuardVariable =
new llvm::GlobalVariable(CGM.getModule(), GuardTy,
false, GV->getLinkage(),
llvm::ConstantInt::get(GuardTy, 0),
GuardVName.str());
GuardVariable->setVisibility(GV->getVisibility());
// Test whether the variable has completed initialization.
llvm::Value *IsInitialized;
// ARM C++ ABI 3.2.3.1:
// To support the potential use of initialization guard variables
// as semaphores that are the target of ARM SWP and LDREX/STREX
// synchronizing instructions we define a static initialization
// guard variable to be a 4-byte aligned, 4- byte word with the
// following inline access protocol.
// #define INITIALIZED 1
// if ((obj_guard & INITIALIZED) != INITIALIZED) {
// if (__cxa_guard_acquire(&obj_guard))
// ...
// }
if (IsARM) {
llvm::Value *V = Builder.CreateLoad(GuardVariable);
V = Builder.CreateAnd(V, Builder.getInt32(1));
IsInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
// Itanium C++ ABI 3.3.2:
// The following is pseudo-code showing how these functions can be used:
// if (obj_guard.first_byte == 0) {
// if ( __cxa_guard_acquire (&obj_guard) ) {
// try {
// ... initialize the object ...;
// } catch (...) {
// __cxa_guard_abort (&obj_guard);
// throw;
// }
// ... queue object destructor with __cxa_atexit() ...;
// __cxa_guard_release (&obj_guard);
// }
// }
} else {
// Load the first byte of the guard variable.
const llvm::Type *PtrTy = Builder.getInt8PtrTy();
llvm::Value *V =
Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp");
IsInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
}
llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
// Check if the first byte of the guard variable is zero.
Builder.CreateCondBr(IsInitialized, InitCheckBlock, EndBlock);
CGF.EmitBlock(InitCheckBlock);
// Variables used when coping with thread-safe statics and exceptions.
if (ThreadsafeStatics) {
// Call __cxa_guard_acquire.
llvm::Value *V
= Builder.CreateCall(getGuardAcquireFn(CGM, GuardPtrTy), GuardVariable);
llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
InitBlock, EndBlock);
// Call __cxa_guard_abort along the exceptional edge.
CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, GuardVariable);
CGF.EmitBlock(InitBlock);
}
// Emit the initializer and add a global destructor if appropriate.
CGF.EmitCXXGlobalVarDeclInit(D, GV);
if (ThreadsafeStatics) {
// Pop the guard-abort cleanup if we pushed one.
CGF.PopCleanupBlock();
// Call __cxa_guard_release. This cannot throw.
Builder.CreateCall(getGuardReleaseFn(CGM, GuardPtrTy), GuardVariable);
} else {
Builder.CreateStore(llvm::ConstantInt::get(GuardTy, 1), GuardVariable);
}
CGF.EmitBlock(EndBlock);
}
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