[LLD][COFF] Allow -arm64xsameaddress in ARM64EC directives (#139631)

Make it a no-op for now, which is sufficient for non-hybrid images.

Fixes #131712.

Author: cjacek

lld/COFF/Driver.cpp

@@ -491,6 +491,12 @@ void LinkerDriver::parseDirectives(InputFile *file) {
     case OPT_alternatename:
       file->symtab.parseAlternateName(arg->getValue());
       break;
+    case OPT_arm64xsameaddress:
+      if (!file->symtab.isEC())
+        Warn(ctx) << arg->getSpelling()
+                  << " is not allowed in non-ARM64EC files (" << toString(file)
+                  << ")";
+      break;
     case OPT_defaultlib:
       if (std::optional<StringRef> path = findLibIfNew(arg->getValue()))
         enqueuePath(*path, false, false);

lld/COFF/Options.td

@@ -356,3 +356,4 @@ def tlbid : P_priv<"tlbid">;
 def tlbout : P_priv<"tlbout">;
 def verbose_all : P_priv<"verbose">;
 def guardsym : P_priv<"guardsym">;
+def arm64xsameaddress : P_priv<"arm64xsameaddress">;

lld/test/COFF/arm64x-sameaddress.test

@@ -0,0 +1,56 @@
+REQUIRES: aarch64
+RUN: split-file %s %t.dir && cd %t.dir
+
+RUN: llvm-mc -filetype=obj -triple=arm64ec-windows func-arm64ec.s -o func-arm64ec.obj
+RUN: llvm-mc -filetype=obj -triple=aarch64-windows func-arm64.s -o func-arm64.obj
+RUN: llvm-mc -filetype=obj -triple=arm64ec-windows drectve.s -o drectve.obj
+RUN: llvm-mc -filetype=obj -triple=aarch64-windows drectve.s -o drectve-arm64.obj
+RUN: llvm-mc -filetype=obj -triple=arm64ec-windows %S/Inputs/loadconfig-arm64ec.s -o loadconfig-arm64ec.obj
+RUN: llvm-mc -filetype=obj -triple=aarch64-windows %S/Inputs/loadconfig-arm64.s -o loadconfig-arm64.obj
+
+RUN: lld-link -machine:arm64x -dll -noentry -out:out.dll loadconfig-arm64.obj loadconfig-arm64ec.obj \
+RUN:          func-arm64.obj func-arm64ec.obj drectve.obj
+
+RUN: lld-link -machine:arm64x -dll -noentry -out:out-cmd.dll loadconfig-arm64.obj loadconfig-arm64ec.obj \
+RUN:          func-arm64.obj func-arm64ec.obj -arm64xsameaddress:func
+
+RUN: lld-link -machine:arm64ec -dll -noentry -out:out-ec.dll loadconfig-arm64ec.obj func-arm64ec.obj drectve.obj
+
+RUN: lld-link -machine:arm64x -dll -noentry -out:out-warn.dll loadconfig-arm64.obj loadconfig-arm64ec.obj \
+RUN:          func-arm64.obj func-arm64ec.obj drectve-arm64.obj 2>&1 | FileCheck --check-prefix=WARN %s
+WARN: lld-link: warning: -arm64xsameaddress: is not allowed in non-ARM64EC files (drectve-arm64.obj)
+
+#--- func-arm64.s
+        .section .text,"xr",discard,func
+        .globl func
+func:
+        mov x0, #1
+        ret
+
+#--- func-arm64ec.s
+        .section .text,"xr",discard,"#func"
+        .globl "#func"
+"#func":
+        mov x0, #2
+        ret
+
+        .weak_anti_dep func
+        .set func,"#func"
+
+        .section .wowthk,"xr",discard,entry_thunk
+        .globl entry_thunk
+entry_thunk:
+        mov x0, #3
+        ret
+
+        .section .test,"dr"
+        .rva func
+
+	.section .hybmp$x,"yi"
+	.symidx "#func"
+	.symidx entry_thunk
+	.word 1
+
+#--- drectve.s
+        .section .drectve, "yn"
+        .ascii " -arm64xsameaddress:func"