[CodeGen] Note where we add ABI-specific args in ctors. NFC.

Meta: The ultimate goal is to teach ExtParameterInfo about
pass_object_size attributes. This is necessary for that, since our
ExtParameterInfo is a bit buggy in C++. I plan to actually make use of
this Prefix/Suffix info in the near future, but I like small
single-purpose changes. Especially when those changes are hard to
actually test...

At the moment, some of our C++-specific CodeGen pretends that ABIs can
only add arguments to the beginning of a function call. This isn't quite
correct: args can be appended to the end, as well. It hasn't mattered
much until now, since we seem to only use this "number of arguments
added" data when calculating the ExtParameterInfo to use when making a
CGFunctionInfo. Said ExtParameterInfo is currently only used for
ParameterABIs (Swift) and ns_consumed (ObjC).

So, this patch allows ABIs to indicate whether args they added were at
the beginning or end of an argument list. We can use this information to
emit ExtParameterInfos more correctly, though like said, that bit is
coming soon.

No tests since this is theoretically a nop.

llvm-svn: 295870

1 files changed, 30 insertions, 23 deletions

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 08302f35d5d..2bb37834f53 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -206,8 +206,9 @@ public:
   // lacks a definition for the destructor, non-base destructors must always
   // delegate to or alias the base destructor.
 
-  void buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
-                              SmallVectorImpl<CanQualType> &ArgTys) override;
+  AddedStructorArgs
+  buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
+                         SmallVectorImpl<CanQualType> &ArgTys) override;
 
   /// Non-base dtors should be emitted as delegating thunks in this ABI.
   bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
@@ -248,11 +249,10 @@ public:
 
   void EmitInstanceFunctionProlog(CodeGenFunction &CGF) override;
 
-  unsigned addImplicitConstructorArgs(CodeGenFunction &CGF,
-                                      const CXXConstructorDecl *D,
-                                      CXXCtorType Type, bool ForVirtualBase,
-                                      bool Delegating,
-                                      CallArgList &Args) override;
+  AddedStructorArgs
+  addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
+                             CXXCtorType Type, bool ForVirtualBase,
+                             bool Delegating, CallArgList &Args) override;
 
   void EmitDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *DD,
                           CXXDtorType Type, bool ForVirtualBase,
@@ -1261,17 +1261,19 @@ void MicrosoftCXXABI::EmitVBPtrStores(CodeGenFunction &CGF,
   }
 }
 
-void
+CGCXXABI::AddedStructorArgs
 MicrosoftCXXABI::buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
                                         SmallVectorImpl<CanQualType> &ArgTys) {
+  AddedStructorArgs Added;
   // TODO: 'for base' flag
   if (T == StructorType::Deleting) {
     // The scalar deleting destructor takes an implicit int parameter.
     ArgTys.push_back(getContext().IntTy);
+    ++Added.Suffix;
   }
   auto *CD = dyn_cast<CXXConstructorDecl>(MD);
   if (!CD)
-    return;
+    return Added;
 
   // All parameters are already in place except is_most_derived, which goes
   // after 'this' if it's variadic and last if it's not.
@@ -1279,11 +1281,16 @@ MicrosoftCXXABI::buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
   const CXXRecordDecl *Class = CD->getParent();
   const FunctionProtoType *FPT = CD->getType()->castAs<FunctionProtoType>();
   if (Class->getNumVBases()) {
-    if (FPT->isVariadic())
+    if (FPT->isVariadic()) {
       ArgTys.insert(ArgTys.begin() + 1, getContext().IntTy);
-    else
+      ++Added.Prefix;
+    } else {
       ArgTys.push_back(getContext().IntTy);
+      ++Added.Suffix;
+    }
   }
+
+  return Added;
 }
 
 void MicrosoftCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
@@ -1493,14 +1500,14 @@ void MicrosoftCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
   }
 }
 
-unsigned MicrosoftCXXABI::addImplicitConstructorArgs(
+CGCXXABI::AddedStructorArgs MicrosoftCXXABI::addImplicitConstructorArgs(
     CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
     bool ForVirtualBase, bool Delegating, CallArgList &Args) {
   assert(Type == Ctor_Complete || Type == Ctor_Base);
 
   // Check if we need a 'most_derived' parameter.
   if (!D->getParent()->getNumVBases())
-    return 0;
+    return AddedStructorArgs{};
 
   // Add the 'most_derived' argument second if we are variadic or last if not.
   const FunctionProtoType *FPT = D->getType()->castAs<FunctionProtoType>();
@@ -1511,13 +1518,13 @@ unsigned MicrosoftCXXABI::addImplicitConstructorArgs(
     MostDerivedArg = llvm::ConstantInt::get(CGM.Int32Ty, Type == Ctor_Complete);
   }
   RValue RV = RValue::get(MostDerivedArg);
-  if (FPT->isVariadic())
+  if (FPT->isVariadic()) {
     Args.insert(Args.begin() + 1,
                 CallArg(RV, getContext().IntTy, /*needscopy=*/false));
-  else
-    Args.add(RV, getContext().IntTy);
-
-  return 1;  // Added one arg.
+    return AddedStructorArgs::prefix(1);
+  }
+  Args.add(RV, getContext().IntTy);
+  return AddedStructorArgs::suffix(1);
 }
 
 void MicrosoftCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
@@ -3918,16 +3925,16 @@ MicrosoftCXXABI::getAddrOfCXXCtorClosure(const CXXConstructorDecl *CD,
   CGF.EmitCallArgs(Args, FPT, llvm::makeArrayRef(ArgVec), CD, IsCopy ? 1 : 0);
 
   // Insert any ABI-specific implicit constructor arguments.
-  unsigned ExtraArgs = addImplicitConstructorArgs(CGF, CD, Ctor_Complete,
-                                                  /*ForVirtualBase=*/false,
-                                                  /*Delegating=*/false, Args);
-
+  AddedStructorArgs ExtraArgs =
+      addImplicitConstructorArgs(CGF, CD, Ctor_Complete,
+                                 /*ForVirtualBase=*/false,
+                                 /*Delegating=*/false, Args);
   // Call the destructor with our arguments.
   llvm::Constant *CalleePtr =
     CGM.getAddrOfCXXStructor(CD, StructorType::Complete);
   CGCallee Callee = CGCallee::forDirect(CalleePtr, CD);
   const CGFunctionInfo &CalleeInfo = CGM.getTypes().arrangeCXXConstructorCall(
-      Args, CD, Ctor_Complete, ExtraArgs);
+      Args, CD, Ctor_Complete, ExtraArgs.Prefix + ExtraArgs.Suffix);
   CGF.EmitCall(CalleeInfo, Callee, ReturnValueSlot(), Args);
 
   Cleanups.ForceCleanup();