[clang] [FatLTO] Detect LLD linker more reliably (PR #128285)

[Vincent Lee via cfe-commits]

https://github.com/thevinster updated https://github.com/llvm/llvm-project/pull/128285

>From b8d961acfa2bf17486d63de9481ff46445d6b38f Mon Sep 17 00:00:00 2001
From: Vincent Lee <leevince at fb.com>
Date: Fri, 21 Feb 2025 20:33:25 -0800
Subject: [PATCH 1/3] [FatLTO] Detect LLD linker more reliably

---
 clang/lib/Driver/ToolChains/CommonArgs.cpp                   | 5 ++---
 .../usr/x86_64-unknown-linux-gnu/bin/lld-wrapper             | 0
 clang/test/Driver/fat-lto-objects.c                          | 3 +++
 3 files changed, 5 insertions(+), 3 deletions(-)
 create mode 100755 clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper

diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 360754bdb3161..4f60287a1142b 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -862,13 +862,12 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
   const llvm::Triple &Triple = ToolChain.getTriple();
   const bool IsOSAIX = Triple.isOSAIX();
   const bool IsAMDGCN = Triple.isAMDGCN();
-  const char *Linker = Args.MakeArgString(ToolChain.GetLinkerPath());
+  StringRef Linker = Args.getLastArgValue(options::OPT_fuse_ld_EQ);
   const Driver &D = ToolChain.getDriver();
   const bool IsFatLTO = Args.hasFlag(options::OPT_ffat_lto_objects,
                                      options::OPT_fno_fat_lto_objects, false);
   const bool IsUnifiedLTO = Args.hasArg(options::OPT_funified_lto);
-  if (llvm::sys::path::filename(Linker) != "ld.lld" &&
-      llvm::sys::path::stem(Linker) != "ld.lld" && !Triple.isOSOpenBSD()) {
+  if (Linker != "lld" && Linker != "lld-link" && !Triple.isOSOpenBSD()) {
     // Tell the linker to load the plugin. This has to come before
     // AddLinkerInputs as gold requires -plugin and AIX ld requires -bplugin to
     // come before any -plugin-opt/-bplugin_opt that -Wl might forward.
diff --git a/clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper b/clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper
new file mode 100755
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/fat-lto-objects.c b/clang/test/Driver/fat-lto-objects.c
index fae64ea7fd1a1..7b87e2b468886 100644
--- a/clang/test/Driver/fat-lto-objects.c
+++ b/clang/test/Driver/fat-lto-objects.c
@@ -49,5 +49,8 @@
 // RUN:   -fuse-ld=lld -flto -ffat-lto-objects -### 2>&1 | FileCheck --check-prefix=LTO %s
 // RUN: %clang --target=x86_64-unknown-linux-gnu --sysroot=%S/Inputs/basic_cross_linux_tree %s \
 // RUN:   -fuse-ld=lld -fno-lto -ffat-lto-objects -### 2>&1 | FileCheck --check-prefix=NOLTO %s
+// RUN: %clang --target=x86_64-unknown-linux-gnu --sysroot=%S/Inputs/basic_cross_linux_tree %s \
+// RUN:   -fuse-ld=lld --ld-path=%S/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper \
+// RUN:   -flto -ffat-lto-objects -### 2>&1 | FileCheck --check-prefix=LTO %s
 // LTO: "--fat-lto-objects"
 // NOLTO-NOT: "--fat-lto-objects"

>From da36ced7d82588da99d6348cde24062a7efa3c54 Mon Sep 17 00:00:00 2001
From: Vincent Lee <leevince at fb.com>
Date: Fri, 21 Feb 2025 20:50:05 -0800
Subject: [PATCH 2/3] Make lld-wrapper a symlink to ld.lld

---
 .../usr/x86_64-unknown-linux-gnu/bin/lld-wrapper                 | 1 +
 1 file changed, 1 insertion(+)
 mode change 100755 => 120000 clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper

diff --git a/clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper b/clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper
deleted file mode 100755
index e69de29bb2d1d..0000000000000
diff --git a/clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper b/clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper
new file mode 120000
index 0000000000000..9b032ee3b3f1d
--- /dev/null
+++ b/clang/test/Driver/Inputs/basic_cross_linux_tree/usr/x86_64-unknown-linux-gnu/bin/lld-wrapper
@@ -0,0 +1 @@
+ld.lld
\ No newline at end of file

>From b03056a9b7737557e4e5fac6333a93d9c4ff67ec Mon Sep 17 00:00:00 2001
From: Vincent Lee <leevince at fb.com>
Date: Sat, 22 Feb 2025 23:18:20 -0800
Subject: [PATCH 3/3] Recover original lld check

---
 clang/lib/Driver/ToolChains/CommonArgs.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 4f60287a1142b..b43472a52038b 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -863,11 +863,14 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
   const bool IsOSAIX = Triple.isOSAIX();
   const bool IsAMDGCN = Triple.isAMDGCN();
   StringRef Linker = Args.getLastArgValue(options::OPT_fuse_ld_EQ);
+  const char *LinkerPath = Args.MakeArgString(ToolChain.GetLinkerPath());
   const Driver &D = ToolChain.getDriver();
   const bool IsFatLTO = Args.hasFlag(options::OPT_ffat_lto_objects,
                                      options::OPT_fno_fat_lto_objects, false);
   const bool IsUnifiedLTO = Args.hasArg(options::OPT_funified_lto);
-  if (Linker != "lld" && Linker != "lld-link" && !Triple.isOSOpenBSD()) {
+  if (Linker != "lld" && Linker != "lld-link" &&
+      llvm::sys::path::filename(LinkerPath) != "ld.lld" &&
+      llvm::sys::path::stem(LinkerPath) != "ld.lld" && !Triple.isOSOpenBSD()) {
     // Tell the linker to load the plugin. This has to come before
     // AddLinkerInputs as gold requires -plugin and AIX ld requires -bplugin to
     // come before any -plugin-opt/-bplugin_opt that -Wl might forward.