[clang][MinGW] Implement -mcrtdll option to switch crt choice

clang/include/clang/Basic/DiagnosticFrontendKinds.td

@@ -393,6 +393,9 @@ def warn_hlsl_langstd_minimal :
           "recommend using %1 instead">,
   InGroup<HLSLDXCCompat>;
 
+def err_unknown_crtdll : Error<"unknown Windows/MinGW C runtime library '%0'">,
+                         DefaultFatal;
+
 // ClangIR frontend errors
 def err_cir_to_cir_transform_failed : Error<
     "CIR-to-CIR transformation failed">, DefaultFatal;

clang/include/clang/Basic/LangOptions.def

@@ -493,6 +493,9 @@ LANGOPT(BoundsSafety, 1, 0, NotCompatible, "Bounds safety extension for C")
 
 LANGOPT(PreserveVec3Type, 1, 0, NotCompatible, "Preserve 3-component vector type")
 
+ENUM_LANGOPT(MinGWCRTDll, WindowsCRTDLLVersion, 4, WindowsCRTDLLVersion::CRTDLL_Default, NotCompatible,
+             "MinGW specific. Controls the __MSVCRT_VERSION and related preprocessor defines.")
+
 #undef LANGOPT
 #undef ENUM_LANGOPT
 #undef VALUE_LANGOPT

clang/include/clang/Basic/LangOptions.h

@@ -164,6 +164,23 @@ class LangOptionsBase {
     MSVC2022_9 = 1939,
   };
 
+  enum WindowsCRTDLLVersion {
+    CRTDLL_Default,
+    CRTDLL,
+    MSVCRT10,
+    MSVCRT20,
+    MSVCRT40,
+    MSVCRTD,
+    MSVCR70,
+    MSVCR71,
+    MSVCR80,
+    MSVCR90,
+    MSVCR100,
+    MSVCR110,
+    MSVCR120,
+    UCRT
+  };
+
   enum SYCLMajorVersion {
     SYCL_None,
     SYCL_2017,

clang/include/clang/Driver/Options.td

@@ -1625,6 +1625,12 @@ defm auto_import : BoolFOption<"auto-import",
   PosFlag<SetTrue, [], [], "MinGW specific. Enable code generation support for "
           "automatic dllimport, and enable support for it in the linker. "
           "Enabled by default.">>;
+def mcrtdll_EQ : Joined<["-"], "mcrtdll=">,
+                 Group<m_Group>,
+                 Visibility<[ClangOption, CC1Option]>,
+                 HelpText<"MinGW specific. Changes preprocessor flags and "
+                          "linker options to use the"
+                          "specified C runtime library.">;
 } // let Flags = [TargetSpecific]
 
 // In the future this option will be supported by other offloading

clang/lib/Basic/Targets/OSTargets.cpp

@@ -141,8 +141,54 @@ static void addMinGWDefines(const llvm::Triple &Triple, const LangOptions &Opts,
     DefineStd(Builder, "WIN64", Opts);
     Builder.defineMacro("__MINGW64__");
   }
-  Builder.defineMacro("__MSVCRT__");
   Builder.defineMacro("__MINGW32__");
+  if (Opts.getMinGWCRTDll() == LangOptions::WindowsCRTDLLVersion::CRTDLL) {
+    Builder.defineMacro("__CRTDLL__");
+  } else {
+    Builder.defineMacro("__MSVCRT__");
+    switch (Opts.getMinGWCRTDll()) {
+    case LangOptions::WindowsCRTDLLVersion::CRTDLL_Default:
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCRT10:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x100");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCRT20:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x200");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCRT40:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x400");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCRTD:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x600");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCR70:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x700");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCR71:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x701");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCR80:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x800");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCR90:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0x900");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCR100:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0xA00");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCR110:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0xB00");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::MSVCR120:
+      Builder.defineMacro("__MSVCRT_VERSION__", "0xC00");
+      break;
+    case LangOptions::WindowsCRTDLLVersion::UCRT:
+      Builder.defineMacro("_UCRT");
+      break;
+    default:
+      llvm_unreachable("Unknown MinGW CRT version");
+    }
+  }
   addCygMingDefines(Opts, Builder);
 }
 

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5970,6 +5970,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (Triple.isWindowsGNUEnvironment()) {
     Args.addOptOutFlag(CmdArgs, options::OPT_fauto_import,
                        options::OPT_fno_auto_import);
+    Args.addLastArg(CmdArgs, options::OPT_mcrtdll_EQ);
   }
 
   if (Args.hasFlag(options::OPT_fms_volatile, options::OPT_fno_ms_volatile,

clang/lib/Driver/ToolChains/MinGW.cpp

@@ -85,19 +85,24 @@ void tools::MinGW::Linker::AddLibGCC(const ArgList &Args,
 
   CmdArgs.push_back("-lmoldname");
   CmdArgs.push_back("-lmingwex");
-  for (auto Lib : Args.getAllArgValues(options::OPT_l)) {
-    if (StringRef(Lib).starts_with("msvcr") ||
-        StringRef(Lib).starts_with("ucrt") ||
-        StringRef(Lib).starts_with("crtdll")) {
-      Lib = (llvm::Twine("-l") + Lib).str();
-      // Respect the user's chosen crt variant, but still provide it
-      // again as the last linker argument, because some of the libraries
-      // we added above may depend on it.
-      CmdArgs.push_back(Args.MakeArgStringRef(Lib));
-      return;
-    }
+
+  if (Arg *A = Args.getLastArg(options::OPT_mcrtdll_EQ)) {
+    std::string mcrtdll = (Twine("-l") + A->getValue()).str();
+    CmdArgs.push_back(Args.MakeArgStringRef(mcrtdll));
+  } else {
+    for (auto Lib : Args.getAllArgValues(options::OPT_l))
+      if (StringRef(Lib).starts_with("msvcr") ||
+          StringRef(Lib).starts_with("ucrt") ||
+          StringRef(Lib).starts_with("crtdll")) {
+        Lib = (llvm::Twine("-l") + Lib).str();
+        // Respect the user's chosen crt variant, but still provide it
+        // again as the last linker argument, because some of the libraries
+        // we added above may depend on it.
+        CmdArgs.push_back(Args.MakeArgStringRef(Lib));
+        return;
+      }
+    CmdArgs.push_back("-lmsvcrt");
   }
-  CmdArgs.push_back("-lmsvcrt");
 }
 
 void tools::MinGW::Linker::ConstructJob(Compilation &C, const JobAction &JA,

clang/lib/Frontend/CompilerInvocation.cpp

@@ -4705,6 +4705,44 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
     }
   }
 
+  // Process MinGW -mcrtdll option
+  if (Arg *A = Args.getLastArg(OPT_mcrtdll_EQ)) {
+    Opts.MinGWCRTDll =
+        llvm::StringSwitch<enum LangOptions::WindowsCRTDLLVersion>(
+            A->getValue())
+            .StartsWithLower("crtdll",
+                             LangOptions::WindowsCRTDLLVersion::CRTDLL)
+            .StartsWithLower("msvcrt10",
+                             LangOptions::WindowsCRTDLLVersion::MSVCRT10)
+            .StartsWithLower("msvcrt20",
+                             LangOptions::WindowsCRTDLLVersion::MSVCRT20)
+            .StartsWithLower("msvcrt40",
+                             LangOptions::WindowsCRTDLLVersion::MSVCRT40)
+            .StartsWithLower("msvcr40",
+                             LangOptions::WindowsCRTDLLVersion::MSVCRT40)
+            .StartsWithLower("msvcrtd",
+                             LangOptions::WindowsCRTDLLVersion::MSVCRTD)
+            .StartsWithLower("msvcr70",
+                             LangOptions::WindowsCRTDLLVersion::MSVCR70)
+            .StartsWithLower("msvcr71",
+                             LangOptions::WindowsCRTDLLVersion::MSVCR71)
+            .StartsWithLower("msvcr80",
+                             LangOptions::WindowsCRTDLLVersion::MSVCR80)
+            .StartsWithLower("msvcr90",
+                             LangOptions::WindowsCRTDLLVersion::MSVCR90)
+            .StartsWithLower("msvcr100",
+                             LangOptions::WindowsCRTDLLVersion::MSVCR100)
+            .StartsWithLower("msvcr110",
+                             LangOptions::WindowsCRTDLLVersion::MSVCR110)
+            .StartsWithLower("msvcr120",
+                             LangOptions::WindowsCRTDLLVersion::MSVCR120)
+            .StartsWithLower("ucrt", LangOptions::WindowsCRTDLLVersion::UCRT)
+            .Default(LangOptions::WindowsCRTDLLVersion::CRTDLL_Default);
+    if (Opts.MinGWCRTDll == LangOptions::WindowsCRTDLLVersion::CRTDLL_Default) {
+      Diags.Report(diag::err_unknown_crtdll) << A->getValue();
+    }
+  }
+
   return Diags.getNumErrors() == NumErrorsBefore;
 }
 

clang/test/Driver/mingw-mcrtdll.c

@@ -0,0 +1,30 @@
+// RUN: %clang -v --target=x86_64-w64-mingw32 -### %s 2>&1 | FileCheck -check-prefix=DEFAULT %s
+// RUN: %clang -v --target=x86_64-w64-mingw32 -mcrtdll=msvcr90 -### %s 2>&1 | FileCheck -check-prefix=MSVCR90 %s
+// RUN: %clang -v --target=x86_64-w64-mingw32 -mcrtdll=msvcr90_suffix -### %s 2>&1 | FileCheck -check-prefix=MSVCR90_SUFFIX %s
+// RUN: %clang -v --target=x86_64-w64-mingw32 -mcrtdll=ucrt -### %s 2>&1 | FileCheck -check-prefix=UCRT %s
+// RUN: %clang -v --target=x86_64-w64-mingw32 -mcrtdll=ucrtbase -### %s 2>&1 | FileCheck -check-prefix=UCRTBASE %s
+
+// RUN: %clang -dM -E --target=x86_64-w64-mingw32 %s 2>&1  | FileCheck -check-prefix=DEFINE_DEFAULT %s
+// RUN: %clang -dM -E --target=x86_64-w64-mingw32 -mcrtdll=msvcr90 %s 2>&1  | FileCheck -check-prefix=DEFINE_MSVCR90 %s
+// RUN: %clang -dM -E --target=x86_64-w64-mingw32 -mcrtdll=msvcr90_suffix %s 2>&1  | FileCheck -check-prefix=DEFINE_MSVCR90 %s
+// RUN: %clang -dM -E --target=x86_64-w64-mingw32 -mcrtdll=ucrt %s 2>&1  | FileCheck -check-prefix=DEFINE_UCRT %s
+// RUN: %clang -dM -E --target=x86_64-w64-mingw32 -mcrtdll=ucrtbase %s 2>&1  | FileCheck -check-prefix=DEFINE_UCRT %s
+// RUN: not %clang -dM -E --target=x86_64-w64-mingw32 -mcrtdll=bad %s 2>&1  | FileCheck -check-prefix=BAD %s
+
+// DEFAULT: "-lmingwex" "-lmsvcrt"
+// DEFINE_DEFAULT: #define __MSVCRT__
+// MSVCR90: "-lmingwex" "-lmsvcr90"
+// DEFINE_MSVCR90: #define __MSVCRT_VERSION__ 0x900
+// DEFINE_MSVCR90: #define __MSVCRT__
+// MSVCR90-NOT: "-lmsvcrt"
+// MSVCR90_SUFFIX: "-lmingwex" "-lmsvcr90_suffix"
+// MSVCR90_SUFFIX-NOT: "-lmsvcrt"
+// UCRT: "-lmingwex" "-lucrt"
+// DEFINE_UCRT: #define _UCRT
+// DEFINE_UCRT-NOT: #define __MSVCRT_VERSION__
+// UCRT-NOT: "-lmsvcrt"
+// UCRTBASE: "-lmingwex" "-lucrtbase"
+// UCRTBASE-NOT: "-lmsvcrt"
+// DEFINE_CRTDLL: #define __CRTDLL__
+// DEFINE_CRTDLL-NOT: #define __MSVCRT__
+// BAD: error: unknown Windows/MinGW C runtime library 'bad'