WindowsARM: ignore calling conventions as described on MSDN

[martell]

Summary

MSDN says that fastcall stdcall and thiscall and vectorcall are all accepted but ignored on ARM and X64

https://msdn.microsoft.com/en-us/library/984x0h58.aspx

MSDN also says that cdecl is accepted but typically ignored

This patch brings ARM in line with how we ignore them for X64

[rnk]

test/Parser/arm-windows-calling-convention-handling.c

2

Keep this test, add a line like this:

// expected-no-diagnostics

And remove the rest of the diagnostic expectations.

[martell]

test/Parser/arm-windows-calling-convention-handling.c

2

Sure I can do that :)

Will I add the same test for x64 as I don't see any?

[rnk]

test/Parser/arm-windows-calling-convention-handling.c

2

Sure, copy-paste the RUN line and replace thumb7 with x86_64.

[martell]

updated to reflect rnk comments

lib/Basic/Targets.cpp

   BuiltinVaListKind getBuiltinVaListKind() const override {
     return TargetInfo::CharPtrBuiltinVaList;
   }
+  CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {
+    switch (CC) {
+    case CC_X86StdCall:
+    case CC_X86ThisCall:
+    case CC_X86FastCall:
+    case CC_X86VectorCall:
+      return CCCR_Ignore;
+    case CC_C:
+      return CCCR_OK;
+    default:
+      return CCCR_Warning;
+    }
+  }
 };
 
 // Windows ARM + Itanium C++ ABI Target

test/Parser/arm-windows-calling-convention-handling.c

-// RUN: %clang_cc1 -triple thumbv7-windows -fms-compatibility -fsyntax-only -verify %s
-
-int __cdecl cdecl(int a, int b, int c, int d) { // expected-warning {{calling convention '__cdecl' ignored for this target}}
-  return a + b + c + d;
-}
-
-float __stdcall stdcall(float a, float b, float c, float d) { // expected-warning {{calling convention '__stdcall' ignored for this target}}
-  return a + b + c + d;
-}
-