[clang] UEFI default ABI (llvm#138364)

Set MS ABI as default ABI for UEFI.

Author: Prabhuk

clang/lib/Driver/ToolChains/Arch/X86.cpp

@@ -122,7 +122,8 @@ void x86::getX86TargetFeatures(const Driver &D, const llvm::Triple &Triple,
   // Claim and report unsupported -mabi=. Note: we don't support "sysv_abi" or
   // "ms_abi" as default function attributes.
   if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_mabi_EQ)) {
-    StringRef DefaultAbi = Triple.isOSWindows() ? "ms" : "sysv";
+    StringRef DefaultAbi =
+        (Triple.isOSWindows() || Triple.isUEFI()) ? "ms" : "sysv";
     if (A->getValue() != DefaultAbi)
       D.Diag(diag::err_drv_unsupported_opt_for_target)
           << A->getSpelling() << Triple.getTriple();

clang/test/Driver/x86-mabi.c

@@ -1,6 +1,8 @@
 // RUN: %clang -### --target=x86_64-windows-msvc -mabi=ms -S %s 2>&1 | FileCheck %s
+// RUN: %clang -### --target=x86_64-uefi -mabi=ms -S %s 2>&1 | FileCheck %s
 // RUN: not %clang -### --target=i386-unknown-linux -mabi=ms -S %s 2>&1 | FileCheck --check-prefix=ERR %s
 // RUN: not %clang -### --target=x86_64-windows-msvc -mabi=sysv -S %s 2>&1 | FileCheck --check-prefix=ERR %s
+// RUN: not %clang -### --target=x86_64-uefi -mabi=sysv -S %s 2>&1 | FileCheck --check-prefix=ERR %s
 // RUN: %clang -### --target=i386-unknown-linux -mabi=sysv -S %s 2>&1 | FileCheck %s
 
 // RUN: %clang -### --target=x86_64-windows-gnu -mabi=ms -S %s 2>&1 | FileCheck %s