1 files changed, 33 insertions, 9 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index b65b659fcc2..428098da263 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -362,18 +362,31 @@ getExtParameterInfosForCall(const FunctionProtoType *proto,
 }
 
 /// Arrange a call to a C++ method, passing the given arguments.
+///
+/// ExtraPrefixArgs is the number of ABI-specific args passed after the `this`
+/// parameter.
+/// ExtraSuffixArgs is the number of ABI-specific args passed at the end of
+/// args.
+/// PassProtoArgs indicates whether `args` has args for the parameters in the
+/// given CXXConstructorDecl.
 const CGFunctionInfo &
 CodeGenTypes::arrangeCXXConstructorCall(const CallArgList &args,
                                         const CXXConstructorDecl *D,
                                         CXXCtorType CtorKind,
-                                        unsigned ExtraArgs) {
+                                        unsigned ExtraPrefixArgs,
+                                        unsigned ExtraSuffixArgs,
+                                        bool PassProtoArgs) {
   // FIXME: Kill copy.
   SmallVector<CanQualType, 16> ArgTypes;
   for (const auto &Arg : args)
     ArgTypes.push_back(Context.getCanonicalParamType(Arg.Ty));
 
+  // +1 for implicit this, which should always be args[0].
+  unsigned TotalPrefixArgs = 1 + ExtraPrefixArgs;
+
   CanQual<FunctionProtoType> FPT = GetFormalType(D);
-  RequiredArgs Required = RequiredArgs::forPrototypePlus(FPT, 1 + ExtraArgs, D);
+  RequiredArgs Required =
+      RequiredArgs::forPrototypePlus(FPT, TotalPrefixArgs + ExtraSuffixArgs, D);
   GlobalDecl GD(D, CtorKind);
   CanQualType ResultType = TheCXXABI.HasThisReturn(GD)
                                ? ArgTypes.front()
@@ -382,8 +395,14 @@ CodeGenTypes::arrangeCXXConstructorCall(const CallArgList &args,
                                      : Context.VoidTy;
 
   FunctionType::ExtInfo Info = FPT->getExtInfo();
-  auto ParamInfos = getExtParameterInfosForCall(FPT.getTypePtr(), 1 + ExtraArgs,
-                                                ArgTypes.size());
+  llvm::SmallVector<FunctionProtoType::ExtParameterInfo, 16> ParamInfos;
+  // If the prototype args are elided, we should only have ABI-specific args,
+  // which never have param info.
+  if (PassProtoArgs && FPT->hasExtParameterInfos()) {
+    // ABI-specific suffix arguments are treated the same as variadic arguments.
+    addExtParameterInfosForCall(ParamInfos, FPT.getTypePtr(), TotalPrefixArgs,
+                                ArgTypes.size());
+  }
   return arrangeLLVMFunctionInfo(ResultType, /*instanceMethod=*/true,
                                  /*chainCall=*/false, ArgTypes, Info,
                                  ParamInfos, Required);
@@ -627,15 +646,20 @@ CodeGenTypes::arrangeBuiltinFunctionDeclaration(CanQualType resultType,
 }
 
 /// Arrange a call to a C++ method, passing the given arguments.
+///
+/// numPrefixArgs is the number of ABI-specific prefix arguments we have. It
+/// does not count `this`.
 const CGFunctionInfo &
 CodeGenTypes::arrangeCXXMethodCall(const CallArgList &args,
                                    const FunctionProtoType *proto,
-                                   RequiredArgs required) {
-  unsigned numRequiredArgs =
-    (proto->isVariadic() ? required.getNumRequiredArgs() : args.size());
-  unsigned numPrefixArgs = numRequiredArgs - proto->getNumParams();
+                                   RequiredArgs required,
+                                   unsigned numPrefixArgs) {
+  assert(numPrefixArgs + 1 <= args.size() &&
+         "Emitting a call with less args than the required prefix?");
+  // Add one to account for `this`. It's a bit awkward here, but we don't count
+  // `this` in similar places elsewhere.
   auto paramInfos =
-    getExtParameterInfosForCall(proto, numPrefixArgs, args.size());
+    getExtParameterInfosForCall(proto, numPrefixArgs + 1, args.size());
 
   // FIXME: Kill copy.
   auto argTypes = getArgTypesForCall(Context, args);