clang+lld: Improve clang+ld.darwinnew.lld interaction, pass -demangle

This patch:
- adds an ld64.lld.darwinnew symlink for lld, to go with f2710d4b576,
  so that `clang -fuse-ld=lld.darwinnew` can be used to test new
  Mach-O lld while it's in bring-up. (The expectation is that we'll
  remove this again once new Mach-O lld is the defauld and only Mach-O
  lld.)
- lets the clang driver know if the linker is lld (currently
  only triggered if `-fuse-ld=lld` or `-fuse-ld=lld.darwinnew` is
  passed). Currently only used for the next point, but could be used
  to implement other features that need close coordination between
  compiler and linker, e.g. having a diag for calling `clang++` instead
  of `clang` when link errors are caused by a missing C++ stdlib.
- lets the clang driver pass `-demangle` to Mach-O lld (both old and
  new), in addition to ld64
- implements -demangle for new Mach-O lld
- changes demangleItanium() to accept _Z, __Z, ___Z, ____Z prefixes
  (and updates one test added in D68014). Mach-O has an extra
  underscore for symbols, and the three (or, on Mach-O, four)
  underscores are used for block names.

Differential Revision: https://reviews.llvm.org/D91884

1 files changed, 9 insertions, 2 deletions

diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index d2a2652..ae1838a 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -548,7 +548,10 @@ std::string ToolChain::GetProgramPath(const char *Name) const {
   return D.GetProgramPath(Name, *this);
 }
 
-std::string ToolChain::GetLinkerPath() const {
+std::string ToolChain::GetLinkerPath(bool *LinkerIsLLD) const {
+  if (LinkerIsLLD)
+    *LinkerIsLLD = false;
+
   // Get -fuse-ld= first to prevent -Wunused-command-line-argument. -fuse-ld= is
   // considered as the linker flavor, e.g. "bfd", "gold", or "lld".
   const Arg* A = Args.getLastArg(options::OPT_fuse_ld_EQ);
@@ -599,8 +602,12 @@ std::string ToolChain::GetLinkerPath() const {
     LinkerName.append(UseLinker);
 
     std::string LinkerPath(GetProgramPath(LinkerName.c_str()));
-    if (llvm::sys::fs::can_execute(LinkerPath))
+    if (llvm::sys::fs::can_execute(LinkerPath)) {
+      if (LinkerIsLLD)
+        // FIXME: Remove lld.darwinnew here once it's the only MachO lld.
+        *LinkerIsLLD = UseLinker == "lld" || UseLinker == "lld.darwinnew";
       return LinkerPath;
+    }
   }
 
   if (A)