[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.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@295870 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 12 deletions

diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index 38918c32bc..9808b47ec3 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -207,8 +207,9 @@ public:
 
   void EmitCXXConstructors(const CXXConstructorDecl *D) override;
 
-  void buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
-                              SmallVectorImpl<CanQualType> &ArgTys) override;
+  AddedStructorArgs
+  buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
+                         SmallVectorImpl<CanQualType> &ArgTys) override;
 
   bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
                               CXXDtorType DT) const override {
@@ -225,11 +226,10 @@ 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,
@@ -1353,7 +1353,7 @@ void ItaniumCXXABI::EmitCXXConstructors(const CXXConstructorDecl *D) {
   }
 }
 
-void
+CGCXXABI::AddedStructorArgs
 ItaniumCXXABI::buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
                                       SmallVectorImpl<CanQualType> &ArgTys) {
   ASTContext &Context = getContext();
@@ -1362,9 +1362,12 @@ ItaniumCXXABI::buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
   // These are Clang types, so we don't need to worry about sret yet.
 
   // Check if we need to add a VTT parameter (which has type void **).
-  if (T == StructorType::Base && MD->getParent()->getNumVBases() != 0)
+  if (T == StructorType::Base && MD->getParent()->getNumVBases() != 0) {
     ArgTys.insert(ArgTys.begin() + 1,
                   Context.getPointerType(Context.VoidPtrTy));
+    return AddedStructorArgs::prefix(1);
+  }
+  return AddedStructorArgs{};
 }
 
 void ItaniumCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
@@ -1429,11 +1432,11 @@ void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
     CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
 }
 
-unsigned ItaniumCXXABI::addImplicitConstructorArgs(
+CGCXXABI::AddedStructorArgs ItaniumCXXABI::addImplicitConstructorArgs(
     CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
     bool ForVirtualBase, bool Delegating, CallArgList &Args) {
   if (!NeedsVTTParameter(GlobalDecl(D, Type)))
-    return 0;
+    return AddedStructorArgs{};
 
   // Insert the implicit 'vtt' argument as the second argument.
   llvm::Value *VTT =
@@ -1441,7 +1444,7 @@ unsigned ItaniumCXXABI::addImplicitConstructorArgs(
   QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
   Args.insert(Args.begin() + 1,
               CallArg(RValue::get(VTT), VTTTy, /*needscopy=*/false));
-  return 1;  // Added one arg.
+  return AddedStructorArgs::prefix(1);  // Added one arg.
 }
 
 void ItaniumCXXABI::EmitDestructorCall(CodeGenFunction &CGF,