[MinGW] Support dllexport on i386

In MinGW configurations (GCC, or clang with a *-windows-gnu target),
the -export directives in the object file contains the undecorated
symbol name, while it is decorated in MSVC configurations. (On the
command line, link.exe takes an undecorated symbol name for the
-export argument though.)

Differential Revision: https://reviews.llvm.org/D37772

llvm-svn: 313174

6 files changed, 35 insertions, 0 deletions

diff --git a/lld/COFF/Config.h b/lld/COFF/Config.h
index 215dad91d97..0b8489b7c53 100644
--- a/lld/COFF/Config.h
+++ b/lld/COFF/Config.h
@@ -173,6 +173,7 @@ struct Configuration {
   bool LargeAddressAware = false;
   bool HighEntropyVA = false;
   bool AppContainer = false;
+  bool MinGW = false;
 };
 
 extern Configuration *Config;
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index e0efb796981..c3dfdb2a399 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -234,6 +234,12 @@ void LinkerDriver::parseDirectives(StringRef S) {
       break;
     case OPT_export: {
       Export E = parseExport(Arg->getValue());
+      if (Config->Machine == I386 && Config->MinGW) {
+        if (!isDecorated(E.Name))
+          E.Name = Saver.save("_" + E.Name);
+        if (!E.ExtName.empty() && !isDecorated(E.ExtName))
+          E.ExtName = Saver.save("_" + E.ExtName);
+      }
       E.Directives = true;
       Config->Exports.push_back(E);
       break;
@@ -719,6 +725,10 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
     return;
   }
 
+  // Handle /lldmingw early, since it can potentially affect how other
+  // options are handled.
+  Config->MinGW = Args.hasArg(OPT_lldmingw);
+
   if (auto *Arg = Args.getLastArg(OPT_linkrepro)) {
     SmallString<64> Path = StringRef(Arg->getValue());
     sys::path::append(Path, "repro.tar");
diff --git a/lld/COFF/Options.td b/lld/COFF/Options.td
index 813686129b0..694639e15dc 100644
--- a/lld/COFF/Options.td
+++ b/lld/COFF/Options.td
@@ -104,6 +104,7 @@ def help_q : Flag<["/?", "-?"], "">, Alias<help>;
 // LLD extensions
 def nopdb : F<"nopdb">, HelpText<"Disable PDB generation for DWARF users">;
 def nosymtab : F<"nosymtab">;
+def lldmingw : F<"lldmingw">;
 def msvclto : F<"msvclto">;
 def rsp_quoting : Joined<["--"], "rsp-quoting=">,
   HelpText<"Quoting style for response files, 'windows' (default) or 'posix'">;
diff --git a/lld/MinGW/Driver.cpp b/lld/MinGW/Driver.cpp
index d0574b8f6ae..41b39b9011a 100644
--- a/lld/MinGW/Driver.cpp
+++ b/lld/MinGW/Driver.cpp
@@ -120,6 +120,7 @@ bool mingw::link(ArrayRef<const char *> ArgsArr, raw_ostream &Diag) {
   auto Add = [&](const Twine &S) { LinkArgs.push_back(S.str()); };
 
   Add("lld-link");
+  Add("-lldmingw");
 
   if (auto *A = Args.getLastArg(OPT_entry)) {
     StringRef S = A->getValue();
diff --git a/lld/test/COFF/dllexport-mingw.s b/lld/test/COFF/dllexport-mingw.s
new file mode 100644
index 00000000000..06c2e225817
--- /dev/null
+++ b/lld/test/COFF/dllexport-mingw.s
@@ -0,0 +1,19 @@
+# REQEUIRES: x86
+
+# RUN: llvm-mc -triple=i686-windows-gnu %s -filetype=obj -o %t.obj
+
+# RUN: lld-link -lldmingw -dll -out:%t.dll -entry:main %t.obj -implib:%t.lib
+# RUN: llvm-readobj %t.lib | FileCheck %s
+
+# CHECK: Symbol: __imp__func
+# CHECK: Symbol: _func
+
+.global _main
+.global _func
+.text
+_main:
+  ret
+_func:
+  ret
+.section .drectve
+.ascii "-export:func"
diff --git a/lld/test/MinGW/driver.test b/lld/test/MinGW/driver.test
index b408d1d142b..daf08613a06 100644
--- a/lld/test/MinGW/driver.test
+++ b/lld/test/MinGW/driver.test
@@ -53,3 +53,6 @@ I386-ENTRY: -entry:DllMainCRTStartup@12
 
 RUN: ld.lld -### -m i386pep foo.o --whole-archive bar.a --no-whole-archive baz.a | FileCheck -check-prefix WHOLE-ARCHIVE %s
 WHOLE-ARCHIVE: foo.o -wholearchive:bar.a baz.a
+
+RUN: ld.lld -### -m i386pep foo.o | FileCheck -check-prefix MINGW-FLAG %s
+MINGW-FLAG: -lldmingw