Generating assumption loads of vptr after ctor call (fixed)
Generating call assume(icmp %vtable, %global_vtable) after constructor
call for devirtualization purposes.
For more info go to:
http://lists.llvm.org/pipermail/cfe-dev/2015-July/044227.html
Edit:
Fixed version because of PR24479.
After this patch got reverted because of ScalarEvolution bug (D12719)
Merged after John McCall big patch (Added Address).
http://reviews.llvm.org/D11859
llvm-svn: 247199
diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index 45ef0f5..dc65b14 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -1984,12 +1984,14 @@
bool ForVirtualBase,
bool Delegating, Address This,
const CXXConstructExpr *E) {
+ const CXXRecordDecl *ClassDecl = D->getParent();
+
// C++11 [class.mfct.non-static]p2:
// If a non-static member function of a class X is called for an object that
// is not of type X, or of a type derived from X, the behavior is undefined.
// FIXME: Provide a source location here.
EmitTypeCheck(CodeGenFunction::TCK_ConstructorCall, SourceLocation(),
- This.getPointer(), getContext().getRecordType(D->getParent()));
+ This.getPointer(), getContext().getRecordType(ClassDecl));
if (D->isTrivial() && D->isDefaultConstructor()) {
assert(E->getNumArgs() == 0 && "trivial default ctor with args");
@@ -2005,7 +2007,7 @@
const Expr *Arg = E->getArg(0);
QualType SrcTy = Arg->getType();
Address Src = EmitLValue(Arg).getAddress();
- QualType DestTy = getContext().getTypeDeclType(D->getParent());
+ QualType DestTy = getContext().getTypeDeclType(ClassDecl);
EmitAggregateCopyCtor(This, Src, DestTy, SrcTy);
return;
}
@@ -2028,6 +2030,48 @@
const CGFunctionInfo &Info =
CGM.getTypes().arrangeCXXConstructorCall(Args, D, Type, ExtraArgs);
EmitCall(Info, Callee, ReturnValueSlot(), Args, D);
+
+ // Generate vtable assumptions if we're constructing a complete object
+ // with a vtable. We don't do this for base subobjects for two reasons:
+ // first, it's incorrect for classes with virtual bases, and second, we're
+ // about to overwrite the vptrs anyway.
+ // We also have to make sure if we can refer to vtable:
+ // - If vtable is external then it's safe to use it (for available_externally
+ // CGVTables will make sure if it can emit it).
+ // - Otherwise we can refer to vtable if it's safe to speculatively emit.
+ // FIXME: If vtable is used by ctor/dtor, we are always safe to refer to it.
+ if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
+ ClassDecl->isDynamicClass() && Type != Ctor_Base &&
+ (CGM.getVTables().isVTableExternal(ClassDecl) ||
+ CGM.getCXXABI().canSpeculativelyEmitVTable(ClassDecl)))
+ EmitVTableAssumptionLoads(ClassDecl, This);
+}
+
+void CodeGenFunction::EmitVTableAssumptionLoad(const VPtr &Vptr, Address This) {
+ llvm::Value *VTableGlobal =
+ CGM.getCXXABI().getVTableAddressPoint(Vptr.Base, Vptr.VTableClass);
+ if (!VTableGlobal)
+ return;
+
+ // We can just use the base offset in the complete class.
+ CharUnits NonVirtualOffset = Vptr.Base.getBaseOffset();
+
+ if (!NonVirtualOffset.isZero())
+ This =
+ ApplyNonVirtualAndVirtualOffset(*this, This, NonVirtualOffset, nullptr,
+ Vptr.VTableClass, Vptr.NearestVBase);
+
+ llvm::Value *VPtrValue = GetVTablePtr(This, VTableGlobal->getType());
+ llvm::Value *Cmp =
+ Builder.CreateICmpEQ(VPtrValue, VTableGlobal, "cmp.vtables");
+ Builder.CreateAssumption(Cmp);
+}
+
+void CodeGenFunction::EmitVTableAssumptionLoads(const CXXRecordDecl *ClassDecl,
+ Address This) {
+ if (CGM.getCXXABI().doStructorsInitializeVPtrs(ClassDecl))
+ for (const VPtr &Vptr : getVTablePointers(ClassDecl))
+ EmitVTableAssumptionLoad(Vptr, This);
}
void
@@ -2193,24 +2237,12 @@
PushDestructorCleanup(D, Addr);
}
-void
-CodeGenFunction::InitializeVTablePointer(BaseSubobject Base,
- const CXXRecordDecl *NearestVBase,
- CharUnits OffsetFromNearestVBase,
- const CXXRecordDecl *VTableClass) {
- const CXXRecordDecl *RD = Base.getBase();
-
- // Don't initialize the vtable pointer if the class is marked with the
- // 'novtable' attribute.
- if ((RD == VTableClass || RD == NearestVBase) &&
- VTableClass->hasAttr<MSNoVTableAttr>())
- return;
-
+void CodeGenFunction::InitializeVTablePointer(const VPtr &Vptr) {
// Compute the address point.
- bool NeedsVirtualOffset;
llvm::Value *VTableAddressPoint =
CGM.getCXXABI().getVTableAddressPointInStructor(
- *this, VTableClass, Base, NearestVBase, NeedsVirtualOffset);
+ *this, Vptr.VTableClass, Vptr.Base, Vptr.NearestVBase);
+
if (!VTableAddressPoint)
return;
@@ -2218,27 +2250,25 @@
llvm::Value *VirtualOffset = nullptr;
CharUnits NonVirtualOffset = CharUnits::Zero();
- if (NeedsVirtualOffset) {
+ if (CGM.getCXXABI().isVirtualOffsetNeededForVTableField(*this, Vptr)) {
// We need to use the virtual base offset offset because the virtual base
// might have a different offset in the most derived class.
- VirtualOffset =
- CGM.getCXXABI().GetVirtualBaseClassOffset(*this, LoadCXXThisAddress(),
- VTableClass, NearestVBase);
- NonVirtualOffset = OffsetFromNearestVBase;
+
+ VirtualOffset = CGM.getCXXABI().GetVirtualBaseClassOffset(
+ *this, LoadCXXThisAddress(), Vptr.VTableClass, Vptr.NearestVBase);
+ NonVirtualOffset = Vptr.OffsetFromNearestVBase;
} else {
// We can just use the base offset in the complete class.
- NonVirtualOffset = Base.getBaseOffset();
+ NonVirtualOffset = Vptr.Base.getBaseOffset();
}
// Apply the offsets.
Address VTableField = LoadCXXThisAddress();
if (!NonVirtualOffset.isZero() || VirtualOffset)
- VTableField = ApplyNonVirtualAndVirtualOffset(*this, VTableField,
- NonVirtualOffset,
- VirtualOffset,
- VTableClass,
- NearestVBase);
+ VTableField = ApplyNonVirtualAndVirtualOffset(
+ *this, VTableField, NonVirtualOffset, VirtualOffset, Vptr.VTableClass,
+ Vptr.NearestVBase);
// Finally, store the address point. Use the same LLVM types as the field to
// support optimization.
@@ -2248,23 +2278,36 @@
->getPointerTo();
VTableField = Builder.CreateBitCast(VTableField, VTablePtrTy->getPointerTo());
VTableAddressPoint = Builder.CreateBitCast(VTableAddressPoint, VTablePtrTy);
+
llvm::StoreInst *Store = Builder.CreateStore(VTableAddressPoint, VTableField);
CGM.DecorateInstruction(Store, CGM.getTBAAInfoForVTablePtr());
}
-void
-CodeGenFunction::InitializeVTablePointers(BaseSubobject Base,
- const CXXRecordDecl *NearestVBase,
- CharUnits OffsetFromNearestVBase,
- bool BaseIsNonVirtualPrimaryBase,
- const CXXRecordDecl *VTableClass,
- VisitedVirtualBasesSetTy& VBases) {
+CodeGenFunction::VPtrsVector
+CodeGenFunction::getVTablePointers(const CXXRecordDecl *VTableClass) {
+ CodeGenFunction::VPtrsVector VPtrsResult;
+ VisitedVirtualBasesSetTy VBases;
+ getVTablePointers(BaseSubobject(VTableClass, CharUnits::Zero()),
+ /*NearestVBase=*/nullptr,
+ /*OffsetFromNearestVBase=*/CharUnits::Zero(),
+ /*BaseIsNonVirtualPrimaryBase=*/false, VTableClass, VBases,
+ VPtrsResult);
+ return VPtrsResult;
+}
+
+void CodeGenFunction::getVTablePointers(BaseSubobject Base,
+ const CXXRecordDecl *NearestVBase,
+ CharUnits OffsetFromNearestVBase,
+ bool BaseIsNonVirtualPrimaryBase,
+ const CXXRecordDecl *VTableClass,
+ VisitedVirtualBasesSetTy &VBases,
+ VPtrsVector &Vptrs) {
// If this base is a non-virtual primary base the address point has already
// been set.
if (!BaseIsNonVirtualPrimaryBase) {
// Initialize the vtable pointer for this base.
- InitializeVTablePointer(Base, NearestVBase, OffsetFromNearestVBase,
- VTableClass);
+ VPtr Vptr = {Base, NearestVBase, OffsetFromNearestVBase, VTableClass};
+ Vptrs.push_back(Vptr);
}
const CXXRecordDecl *RD = Base.getBase();
@@ -2302,11 +2345,10 @@
BaseDeclIsNonVirtualPrimaryBase = Layout.getPrimaryBase() == BaseDecl;
}
- InitializeVTablePointers(BaseSubobject(BaseDecl, BaseOffset),
- I.isVirtual() ? BaseDecl : NearestVBase,
- BaseOffsetFromNearestVBase,
- BaseDeclIsNonVirtualPrimaryBase,
- VTableClass, VBases);
+ getVTablePointers(
+ BaseSubobject(BaseDecl, BaseOffset),
+ I.isVirtual() ? BaseDecl : NearestVBase, BaseOffsetFromNearestVBase,
+ BaseDeclIsNonVirtualPrimaryBase, VTableClass, VBases, Vptrs);
}
}
@@ -2316,11 +2358,9 @@
return;
// Initialize the vtable pointers for this class and all of its bases.
- VisitedVirtualBasesSetTy VBases;
- InitializeVTablePointers(BaseSubobject(RD, CharUnits::Zero()),
- /*NearestVBase=*/nullptr,
- /*OffsetFromNearestVBase=*/CharUnits::Zero(),
- /*BaseIsNonVirtualPrimaryBase=*/false, RD, VBases);
+ if (CGM.getCXXABI().doStructorsInitializeVPtrs(RD))
+ for (const VPtr &Vptr : getVTablePointers(RD))
+ InitializeVTablePointer(Vptr);
if (RD->getNumVBases())
CGM.getCXXABI().initializeHiddenVirtualInheritanceMembers(*this, RD);