From 413d8cac1a6980a3fd26bf12da15e53521507b58 Mon Sep 17 00:00:00 2001
From: Reid Kleckner <reid@kleckner.net>
Date: Thu, 26 Feb 2015 19:43:46 +0000
Subject: [PATCH] Win64: Silently ignore __stdcall, __fastcall, and __thiscall

MSVC doesn't warn on this. Users are expected to apply the WINAPI macro
to functions passed by pointer to the Win32 API, and this macro expands
to __stdcall. This means we end up with a lot of useless noisy warnings
about ignored calling conventions when compiling code with clang for
Win64.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@230668 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/TargetInfo.h       |  3 ++-
 lib/Basic/Targets.cpp                  | 20 ++++++++++++++++----
 lib/Sema/SemaDeclAttr.cpp              |  7 +++++--
 test/Sema/MicrosoftCompatibility-x64.c | 13 +++++++++----
 4 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/include/clang/Basic/TargetInfo.h b/include/clang/Basic/TargetInfo.h
index e00e0f5a58..bda132e499 100644
--- a/include/clang/Basic/TargetInfo.h
+++ b/include/clang/Basic/TargetInfo.h
@@ -842,7 +842,8 @@ public:
 
   enum CallingConvCheckResult {
     CCCR_OK,
-    CCCR_Warning
+    CCCR_Warning,
+    CCCR_Ignore,
   };
 
   /// \brief Determines whether a given calling convention is valid for the
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index 03cd853d66..a7c8413dd9 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -3626,19 +3626,31 @@ public:
     IntPtrType = SignedLongLong;
     this->UserLabelPrefix = "";
   }
+
   void getTargetDefines(const LangOptions &Opts,
                                 MacroBuilder &Builder) const override {
     WindowsTargetInfo<X86_64TargetInfo>::getTargetDefines(Opts, Builder);
     Builder.defineMacro("_WIN64");
   }
+
   BuiltinVaListKind getBuiltinVaListKind() const override {
     return TargetInfo::CharPtrBuiltinVaList;
   }
+
   CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {
-    return (CC == CC_C ||
-            CC == CC_X86VectorCall ||
-            CC == CC_IntelOclBicc ||
-            CC == CC_X86_64SysV) ? CCCR_OK : CCCR_Warning;
+    switch (CC) {
+    case CC_X86StdCall:
+    case CC_X86ThisCall:
+    case CC_X86FastCall:
+      return CCCR_Ignore;
+    case CC_C:
+    case CC_X86VectorCall:
+    case CC_IntelOclBicc:
+    case CC_X86_64SysV:
+      return CCCR_OK;
+    default:
+      return CCCR_Warning;
+    }
   }
 };
 } // end anonymous namespace
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 7af4bd28d5..4552ad9609 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -3393,9 +3393,12 @@ bool Sema::CheckCallingConvAttr(const AttributeList &attr, CallingConv &CC,
 
   const TargetInfo &TI = Context.getTargetInfo();
   TargetInfo::CallingConvCheckResult A = TI.checkCallingConvention(CC);
-  if (A == TargetInfo::CCCR_Warning) {
-    Diag(attr.getLoc(), diag::warn_cconv_ignored) << attr.getName();
+  if (A != TargetInfo::CCCR_OK) {
+    if (A == TargetInfo::CCCR_Warning)
+      Diag(attr.getLoc(), diag::warn_cconv_ignored) << attr.getName();
 
+    // This convention is not valid for the target. Use the default function or
+    // method calling convention.
     TargetInfo::CallingConvMethodType MT = TargetInfo::CCMT_Unknown;
     if (FD)
       MT = FD->isCXXInstanceMember() ? TargetInfo::CCMT_Member : 
diff --git a/test/Sema/MicrosoftCompatibility-x64.c b/test/Sema/MicrosoftCompatibility-x64.c
index bf595af699..7d1f64996e 100644
--- a/test/Sema/MicrosoftCompatibility-x64.c
+++ b/test/Sema/MicrosoftCompatibility-x64.c
@@ -1,8 +1,13 @@
-// RUN: %clang_cc1 %s -fsyntax-only -Wno-unused-value -Wmicrosoft -verify -fms-compatibility -triple x86_64-pc-win32
-int __stdcall f(void); /* expected-warning {{calling convention '__stdcall' ignored for this target}} */
+// RUN: %clang_cc1 %s -Wmicrosoft -verify -fms-compatibility -triple x86_64-pc-win32
 
-/* This should compile without warning because __stdcall is treated
-as __cdecl in MS compatibility mode for x64 compiles*/
+// None of these should warn. stdcall is treated as equivalent to cdecl on
+// x64.
+// expected-no-diagnostics
+
+int __stdcall f(void);
 int __cdecl f(void) {
   return 0;
 }
+int __stdcall func_std(void);
+int __thiscall func_this(void);
+int __fastcall func_fast(void);
-- 
2.40.0