[Clang] Add the ability to map DLL storage class to visibility

For PlayStation we offer source code compatibility with
Microsoft's dllimport/export annotations; however, our file
format is based on ELF.

To support this we translate from DLL storage class to ELF
visibility at the end of codegen in Clang.

Other toolchains have used similar strategies (e.g. see the
documentation for this ARM toolchain:

https://developer.arm.com/documentation/dui0530/i/migrating-from-rvct-v3-1-to-rvct-v4-0/changes-to-symbol-visibility-between-rvct-v3-1-and-rvct-v4-0)

This patch adds the ability to perform this translation. Options
are provided to support customizing the mapping behaviour.

Differential Revision: https://reviews.llvm.org/D89970

1 files changed, 32 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 3c0ba31..7b8554c 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2814,6 +2814,38 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   if (Args.hasArg(OPT_fapply_global_visibility_to_externs))
     Opts.SetVisibilityForExternDecls = 1;
 
+  if (Args.hasArg(OPT_fvisibility_from_dllstorageclass)) {
+    Opts.VisibilityFromDLLStorageClass = 1;
+
+    // Translate dllexport defintions to default visibility, by default.
+    if (Arg *O = Args.getLastArg(OPT_fvisibility_dllexport_EQ))
+      Opts.setDLLExportVisibility(parseVisibility(O, Args, Diags));
+    else
+      Opts.setDLLExportVisibility(DefaultVisibility);
+
+    // Translate defintions without an explict DLL storage class to hidden
+    // visibility, by default.
+    if (Arg *O = Args.getLastArg(OPT_fvisibility_nodllstorageclass_EQ))
+      Opts.setNoDLLStorageClassVisibility(parseVisibility(O, Args, Diags));
+    else
+      Opts.setNoDLLStorageClassVisibility(HiddenVisibility);
+
+    // Translate dllimport external declarations to default visibility, by
+    // default.
+    if (Arg *O = Args.getLastArg(OPT_fvisibility_externs_dllimport_EQ))
+      Opts.setExternDeclDLLImportVisibility(parseVisibility(O, Args, Diags));
+    else
+      Opts.setExternDeclDLLImportVisibility(DefaultVisibility);
+
+    // Translate external declarations without an explicit DLL storage class
+    // to hidden visibility, by default.
+    if (Arg *O = Args.getLastArg(OPT_fvisibility_externs_nodllstorageclass_EQ))
+      Opts.setExternDeclNoDLLStorageClassVisibility(
+          parseVisibility(O, Args, Diags));
+    else
+      Opts.setExternDeclNoDLLStorageClassVisibility(HiddenVisibility);
+  }
+
   if (Args.hasArg(OPT_ftrapv)) {
     Opts.setSignedOverflowBehavior(LangOptions::SOB_Trapping);
     // Set the handler, if one is specified.