[clang][Driver] Pass -machine argument to the linker explicitly for ARM64EC targets. (#86835)

This is required by the linker. Also add a new -marm64x command line argument to allow specifying -machine:arm64x.

Author: cjacek

clang/include/clang/Driver/Options.td

@@ -4510,6 +4510,9 @@ def mwindows : Joined<["-"], "mwindows">, Group<m_Group>;
 def mdll : Joined<["-"], "mdll">, Group<m_Group>;
 def municode : Joined<["-"], "municode">, Group<m_Group>;
 def mthreads : Joined<["-"], "mthreads">, Group<m_Group>;
+def marm64x : Joined<["-"], "marm64x">, Group<m_Group>,
+  Visibility<[ClangOption, CLOption]>,
+  HelpText<"Link as a hybrid ARM64X image">;
 def mguard_EQ : Joined<["-"], "mguard=">, Group<m_Group>,
   HelpText<"Enable or disable Control Flow Guard checks and guard tables emission">,
   Values<"none,cf,cf-nochecks">;

clang/lib/Driver/ToolChains/MSVC.cpp

@@ -79,6 +79,11 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(
         Args.MakeArgString(std::string("-out:") + Output.getFilename()));
 
+  if (Args.hasArg(options::OPT_marm64x))
+    CmdArgs.push_back("-machine:arm64x");
+  else if (TC.getTriple().isWindowsArm64EC())
+    CmdArgs.push_back("-machine:arm64ec");
+
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles) &&
       !C.getDriver().IsCLMode() && !C.getDriver().IsFlangMode()) {
     CmdArgs.push_back("-defaultlib:libcmt");
@@ -1017,4 +1022,7 @@ void MSVCToolChain::addClangTargetOptions(
   if (DriverArgs.hasFlag(options::OPT_fno_rtti, options::OPT_frtti,
                          /*Default=*/false))
     CC1Args.push_back("-D_HAS_STATIC_RTTI=0");
+
+  if (Arg *A = DriverArgs.getLastArgNoClaim(options::OPT_marm64x))
+    A->ignoreTargetSpecific();
 }

clang/test/Driver/msvc-link.c

@@ -36,3 +36,23 @@
 // VFSOVERLAY: "--vfsoverlay"
 // VFSOVERLAY: lld-link
 // VFSOVERLAY: "/vfsoverlay:{{.*}}" "{{.*}}.obj"
+
+// RUN: %clang -target arm64ec-pc-windows-msvc -fuse-ld=link -### %s 2>&1 | FileCheck --check-prefix=ARM64EC %s
+// RUN: %clang_cl -target arm64ec-pc-windows-msvc -fuse-ld=link -### %s 2>&1 | FileCheck --check-prefix=ARM64EC %s
+// RUN: %clang_cl -arm64EC -fuse-ld=link -### %s 2>&1 | FileCheck --check-prefix=ARM64EC %s
+// ARM64EC: "-machine:arm64ec"
+
+// RUN: %clang -target arm64ec-pc-windows-msvc -fuse-ld=link -marm64x -### %s 2>&1 | \
+// RUN:        FileCheck --check-prefix=ARM64X %s
+// RUN: %clang -target aarch64-pc-windows-msvc -fuse-ld=link -marm64x -### %s 2>&1 | \
+// RUN:        FileCheck --check-prefix=ARM64X %s
+// RUN: %clang_cl -marm64x -fuse-ld=link -### %s 2>&1 | FileCheck --check-prefix=ARM64X %s
+// RUN: %clang_cl -arm64EC -marm64x -fuse-ld=link -### %s 2>&1 | FileCheck --check-prefix=ARM64X %s
+// ARM64X: "-machine:arm64x"
+
+// RUN: not %clang -target x86_64-linux-gnu -marm64x -### %s 2>&1 | FileCheck --check-prefix=HYBRID-ERR %s
+// HYBRID-ERR: error: unsupported option '-marm64x' for target 'x86_64-linux-gnu'
+
+// RUN: %clang -c -marm64x  -target arm64ec-pc-windows-msvc -fuse-ld=link -### %s 2>&1 | \
+// RUN:        FileCheck --check-prefix=HYBRID-WARN %s
+// HYBRID-WARN: warning: argument unused during compilation: '-marm64x' [-Wunused-command-line-argument]