[clang] [clang][MinGW] Implement -mcrtdll option to switch crt choice (PR #149469)

[Martin Storsjö via cfe-commits]

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@@ -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)
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mstorsjo wrote:

You're missing a case (and enum) for `msvcrt-os`, if this is to mimic the GCC implementation.

https://github.com/llvm/llvm-project/pull/149469