[Clang][MinGW][cygwin] Fix __declspec with -fdeclspec enabled

[alvinhochun]

Summary

Fixes https://github.com/llvm/llvm-project/issues/49958

[rnk]

lgtm

clang/lib/Basic/Targets.cpp

void defineCPUMacros(MacroBuilder &Builder, StringRef CPUName, bool Tuning) {
   Builder.defineMacro("__" + CPUName);
   Builder.defineMacro("__" + CPUName + "__");
   if (Tuning)
     Builder.defineMacro("__tune_" + CPUName + "__");
 }
 
 void addCygMingDefines(const LangOptions &Opts, MacroBuilder &Builder) {
   // Mingw and cygwin define __declspec(a) to __attribute__((a)).  Clang
-  // supports __declspec natively under -fms-extensions, but we define a no-op
-  // __declspec macro anyway for pre-processor compatibility.
-  if (Opts.MicrosoftExt)
+  // supports __declspec natively under -fdeclspec (also enabled with
+  // -fms-extensions), but we define a no-op __declspec macro anyway for
+  // pre-processor compatibility.
+  if (Opts.DeclSpecKeyword)
     Builder.defineMacro("__declspec", "__declspec");
   else
     Builder.defineMacro("__declspec(a)", "__attribute__((a))");
 
   if (!Opts.MicrosoftExt) {
     // Provide macros for all the calling convention keywords.  Provide both
     // single and double underscore prefixed variants.  These are available on
     // x64 as well as x86, even though they have no effect.

clang/test/Preprocessor/init-x86.c

 // I386-NETBSD:#define __WCHAR_TYPE__ int
 // I386-NETBSD:#define __WCHAR_WIDTH__ 32
 // I386-NETBSD:#define __WINT_TYPE__ int
 // I386-NETBSD:#define __WINT_WIDTH__ 32
 // I386-NETBSD:#define __i386 1
 // I386-NETBSD:#define __i386__ 1
 // I386-NETBSD:#define i386 1
 
-// RUN: %clang_cc1 -E -dM -triple=i686-pc-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC %s
-// RUN: %clang_cc1 -E -dM -fms-extensions -triple=i686-pc-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC %s
-// RUN: %clang_cc1 -E -dM -triple=i686-unknown-cygwin < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC %s
-// RUN: %clang_cc1 -E -dM -fms-extensions -triple=i686-unknown-cygwin < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC %s
-// I386-DECLSPEC: #define __declspec{{.*}}
+// RUN: %clang_cc1 -E -dM -triple=i686-pc-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC-GNU %s
+// RUN: %clang_cc1 -E -dM -triple=i686-unknown-cygwin < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC-GNU %s
+// I386-DECLSPEC-GNU: #define __declspec{{.*}} __attribute__{{.*}}
+
+// RUN: %clang_cc1 -E -dM -fms-extensions -triple=i686-pc-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC-MS %s
+// RUN: %clang_cc1 -E -dM -fdeclspec -triple=i686-pc-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC-MS %s
+// RUN: %clang_cc1 -E -dM -fms-extensions -triple=i686-unknown-cygwin < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC-MS %s
+// RUN: %clang_cc1 -E -dM -fdeclspec -triple=i686-unknown-cygwin < /dev/null | FileCheck -match-full-lines -check-prefix I386-DECLSPEC-MS %s
+// I386-DECLSPEC-MS: #define __declspec{{.*}} __declspec{{.*}}
 
 //
 // RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix X86_64 %s
 // RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix X86_64 -check-prefix X86_64-CXX %s
 //
 // X86_64:#define _LP64 1
 // X86_64-NOT:#define _LP32 1
 // X86_64:#define __BIGGEST_ALIGNMENT__ 16

clang/test/Preprocessor/init.c

 // PS4:#define __x86_64 1
 // PS4:#define __x86_64__ 1
 // PS4:#define unix 1
 //
 // RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=x86_64-scei-ps4 < /dev/null | FileCheck --match-full-lines --check-prefix PS4-CXX %s
 // RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=x86_64-sie-ps5 < /dev/null | FileCheck --match-full-lines --check-prefix PS4-CXX %s
 // PS4-CXX:#define __STDCPP_DEFAULT_NEW_ALIGNMENT__ 32UL
 //
-// RUN: %clang_cc1 -E -dM -triple=x86_64-pc-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix X86-64-DECLSPEC %s
-// RUN: %clang_cc1 -E -dM -fms-extensions -triple=x86_64-unknown-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix X86-64-DECLSPEC %s
-// X86-64-DECLSPEC: #define __declspec{{.*}}
+// RUN: %clang_cc1 -E -dM -triple=x86_64-pc-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix X86-64-DECLSPEC-GNU %s
+// X86-64-DECLSPEC-GNU: #define __declspec{{.*}} __attribute__{{.*}}
+//
+// RUN: %clang_cc1 -E -dM -fms-extensions -triple=x86_64-unknown-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix X86-64-DECLSPEC-MS %s
+// RUN: %clang_cc1 -E -dM -fdeclspec -triple=x86_64-unknown-mingw32 < /dev/null | FileCheck -match-full-lines -check-prefix X86-64-DECLSPEC-MS %s
+// X86-64-DECLSPEC-MS: #define __declspec{{.*}} __declspec{{.*}}
 //
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=sparc64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix SPARCV9 %s
 // SPARCV9:#define __BIGGEST_ALIGNMENT__ 16
 // SPARCV9:#define __INT64_TYPE__ long int
 // SPARCV9:#define __INTMAX_C_SUFFIX__ L
 // SPARCV9:#define __INTMAX_TYPE__ long int
 // SPARCV9:#define __INTPTR_TYPE__ long int
 // SPARCV9:#define __LONG_MAX__ 9223372036854775807L