[ARM64] [Windows] Follow MS X86_64 C++ ABI when passing structs

Summary: Microsoft's C++ object model for ARM64 is the same as that for X86_64.
For example, small structs with non-trivial copy constructors or virtual
function tables are passed indirectly.  Currently, they are passed in registers
when compiled with clang.

Reviewers: rnk, mstorsjo, TomTan, haripul, javed.absar

Reviewed By: rnk, mstorsjo

Subscribers: kristof.beyls, chrib, llvm-commits, cfe-commits

Differential Revision: https://reviews.llvm.org/D49770

llvm-svn: 338076

3 files changed, 8 insertions, 1 deletions

diff --git a/clang/lib/Basic/Targets/AArch64.cpp b/clang/lib/Basic/Targets/AArch64.cpp
index 1665a214354..3444591ac59 100644
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -533,6 +533,11 @@ void MicrosoftARM64TargetInfo::getTargetDefines(const LangOptions &Opts,
   getVisualStudioDefines(Opts, Builder);
 }
 
+TargetInfo::CallingConvKind
+MicrosoftARM64TargetInfo::getCallingConvKind(bool ClangABICompat4) const {
+  return CCK_MicrosoftWin64;
+}
+
 MinGWARM64TargetInfo::MinGWARM64TargetInfo(const llvm::Triple &Triple,
                                            const TargetOptions &Opts)
     : WindowsARM64TargetInfo(Triple, Opts) {
diff --git a/clang/lib/Basic/Targets/AArch64.h b/clang/lib/Basic/Targets/AArch64.h
index f493ff28d31..a9df895e4da 100644
--- a/clang/lib/Basic/Targets/AArch64.h
+++ b/clang/lib/Basic/Targets/AArch64.h
@@ -126,6 +126,8 @@ public:
                               MacroBuilder &Builder) const;
   void getTargetDefines(const LangOptions &Opts,
                         MacroBuilder &Builder) const override;
+  TargetInfo::CallingConvKind
+  getCallingConvKind(bool ClangABICompat4) const override;
 };
 
 // ARM64 MinGW target
diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
index dd04dee0871..b6cb27977b6 100644
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -752,7 +752,7 @@ public:
 
   TargetInfo::CallingConvKind
   getCallingConvKind(bool ClangABICompat4) const override {
-    return CCK_MicrosoftX86_64;
+    return CCK_MicrosoftWin64;
   }
 };