[PATCH] D69769: [Clang][Driver] Don't pun -fuse-ld=lld as -fuse-ld=lld-link with msvc

[John Ericson via Phabricator via cfe-commits]

Ericson2314 created this revision.
Herald added subscribers: cfe-commits, mstorsjo.
Herald added a project: clang.

Besides the Mingw toolchain, there is also the CrossWindows toolchain,
which means GNU-style cli but genuine windows headers + libraries. LLD's
MinGW driver is as good a fit as binutil's ld, but there is no easy way
to select it when lld was being rewritten to lld-link.

This makes lld always be the GNU-style one, consistent with the non-msvc
case. It's a small breaking change for Windows, but the only
straightforward way.

It may seem silly to worry about the gnu-style flags, but it is useful
for mixing software designed with MinGW in mind with "real" windows
software that needs a MSVC C++ ABI, C++ threads, etc.

Testing in conjunction with https://github.com/NixOS/nixpkgs/pull/72366,
which might be the first fully automated way to cross compile to
Windows.  I haven't taught Nixpkgs to wrap clang-cl like it wraps clang,
so even for some packages that have separate MSVC and MinGW builds
systems (e.g. zlib, opensll), I seem to be having better luck with the
MinGW-style builds so am going with that.

Backport of D69760 <https://reviews.llvm.org/D69760> for release 8


Repository:
  rC Clang

https://reviews.llvm.org/D69769

Files:
  lib/Driver/Driver.cpp
  lib/Driver/ToolChains/MSVC.cpp
  test/Driver/fuse-ld.c


Index: test/Driver/fuse-ld.c
===================================================================
--- test/Driver/fuse-ld.c
+++ test/Driver/fuse-ld.c
@@ -78,8 +78,13 @@
 // RUN: %clang %s -### -fuse-ld=lld \
 // RUN:     -target i686-unknown-windows-msvc 2>&1 \
 // RUN:   | FileCheck %s --check-prefix CHECK-WINDOWS-MSVC-LLD
-// CHECK-WINDOWS-MSVC-LLD: "{{.*}}lld-link"
-// CHECK-WINDOWS-MSVC-LLD-SAME: "-out:{{.*}}"
+// CHECK-WINDOWS-MSVC-LLD: "{{.*}}ld.lld"
+// CHECK-WINDOWS-MSVC-LLD-SAME: "-o"
+
+// RUN: %clang-cl %s -### -fuse-ld=lld \
+// RUN:   | FileCheck %s --check-prefix CHECK-WINDOWS-MSVC-LLD
+// CHECK-cl-WINDOWS-MSVC-LLD: "{{.*}}ld.lld"
+// CHECK-cl-WINDOWS-MSVC-LLD-SAME: "-o"
 
 // RUN: %clang %s -### -fuse-ld=lld-link \
 // RUN:     -target i686-unknown-windows-msvc 2>&1 \
Index: lib/Driver/ToolChains/MSVC.cpp
===================================================================
--- lib/Driver/ToolChains/MSVC.cpp
+++ lib/Driver/ToolChains/MSVC.cpp
@@ -475,13 +475,10 @@
 
   std::vector<const char *> Environment;
 
-  // We need to special case some linker paths.  In the case of lld, we need to
-  // translate 'lld' into 'lld-link', and in the case of the regular msvc
+  // We need to special case some linker paths.  In the case of the regular msvc
   // linker, we need to use a special search algorithm.
   llvm::SmallString<128> linkPath;
   StringRef Linker = Args.getLastArgValue(options::OPT_fuse_ld_EQ, "link");
-  if (Linker.equals_lower("lld"))
-    Linker = "lld-link";
 
   if (Linker.equals_lower("link")) {
     // If we're using the MSVC linker, it's not sufficient to just use link
Index: lib/Driver/Driver.cpp
===================================================================
--- lib/Driver/Driver.cpp
+++ lib/Driver/Driver.cpp
@@ -4592,8 +4592,8 @@
         break;
       case llvm::Triple::MSVC:
       case llvm::Triple::UnknownEnvironment:
-        if (Args.getLastArgValue(options::OPT_fuse_ld_EQ)
-                .startswith_lower("bfd"))
+        auto linkerFlavor = Args.getLastArgValue(options::OPT_fuse_ld_EQ);
+        if (linkerFlavor.startswith_lower("bfd") || linkerFlavor.equals_lower("lld"))
           TC = llvm::make_unique<toolchains::CrossWindowsToolChain>(
               *this, Target, Args);
         else


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