[LLD] [MinGW] Handle the --dll option

[mstorsjo]

Treat this as an alias for the --shared option.

In practice in GNU ld, they aren't exact aliases but there are small subtle differences in what happens and what doesn't, when they are set, but those differences are probably not intended by users who might be using the --dll option (which gets passed by -mdll in the compiler driver), and the differences are within the area where small details differ between LLD and GNU ld anyway.

[llvmbot]

@llvm/pr-subscribers-platform-windows

@llvm/pr-subscribers-lld

Changes

Treat this as an alias for the --shared option.

In practice in GNU ld, they aren't exact aliases but there are small subtle differences in what happens and what doesn't, when they are set, but those differences are probably not intended by users who might be using the --dll option (which gets passed by -mdll in the compiler driver), and the differences are within the area where small details differ between LLD and GNU ld anyway.

---

Full diff: https://github.com/llvm/llvm-project/pull/68575.diff

2 Files Affected:

• (modified) lld/MinGW/Options.td (+1)
• (modified) lld/test/MinGW/driver.test (+1)

diff --git a/lld/MinGW/Options.td b/lld/MinGW/Options.td
index f59bd5bc38a8db8..fa4c4ecc75d6543 100644
--- a/lld/MinGW/Options.td
+++ b/lld/MinGW/Options.td
@@ -203,6 +203,7 @@ def alias_Bdynamic_dy: Flag<["-"], "dy">, Alias<Bdynamic>;
 def alias_Bstatic_dn: Flag<["-"], "dn">, Alias<Bstatic>;
 def alias_Bstatic_non_shared: Flag<["-"], "non_shared">, Alias<Bstatic>;
 def alias_Bstatic_static: Flag<["-"], "static">, Alias<Bstatic>;
+def alias_dll: F<"dll">, Alias<shared>;
 def alias_entry_e: JoinedOrSeparate<["-"], "e">, Alias<entry>;
 def alias_no_dynamicbase: F<"no-dynamicbase">, Alias<disable_dynamicbase>;
 def alias_strip_s: Flag<["-"], "s">, Alias<strip_all>;
diff --git a/lld/test/MinGW/driver.test b/lld/test/MinGW/driver.test
index 2893f8c66fd122c..1fdd494754af4bf 100644
--- a/lld/test/MinGW/driver.test
+++ b/lld/test/MinGW/driver.test
@@ -27,6 +27,7 @@ ARM64-SAME: foo.o
 
 RUN: ld.lld -### foo.o -m i386pep -shared 2>&1 | FileCheck -check-prefix=SHARED %s
 RUN: ld.lld -### foo.o -m i386pep --shared 2>&1 | FileCheck -check-prefix=SHARED %s
+RUN: ld.lld -### foo.o -m i386pep --dll 2>&1 | FileCheck -check-prefix=SHARED %s
 SHARED:      -out:a.dll
 SHARED-SAME: -dll
 

[zero9178]

LGTM

Given that LDs doc say that it is basically equal to using -shared and that that is the only way users should use it, implementing implementation details of LD doesn't make sense to me unless really really often used in the wild.

[tru]

LGTM