[flang][Driver] Enable FLANG_DEFAULT_LINKER

[parabola94]

The default linker can be changed by a CMake variable CLANG_DEFAULT_LINKER. However, it also changes the default linker invoked by clang. In fact, there already exists FLANG_DEFAULT_LINKER, but it does not work. This patch fixes it.

Note that FLANG_DEFAULT_LINKER will have the same value as CLANG_DEFAULT_LINKER unless it is defined explicitly. That means this patch does not affect the current behavior.

Fixes #73153

[tarunprabhu]

Thanks. LGTM, but please wait for someone on the clang side to take a look as well.

[EDIT] Ah, didn't notice that it was a draft. Let me know when you think it is ready.

[llvmbot]

@llvm/pr-subscribers-flang-driver

Author: None (parabola94)

Changes

The default linker can be changed by a CMake variable CLANG_DEFAULT_LINKER at this moment. However, it also changes the default linker invoked by clang. In fact, there already exists FLANG_DEFAULT_LINKER, but it does not work. This patch fixes it.

Note that FLANG_DEFAULT_LINKER will have the same value as CLANG_DEFAULT_LINKER unless it is defined explicitly. That means this patch does not affect the current behavior.

Fixes #73153

---

Full diff: https://github.com/llvm/llvm-project/pull/149786.diff

4 Files Affected:

• (modified) flang/CMakeLists.txt (+1-1)
• (modified) flang/include/flang/Config/config.h.cmake (+9-7)
• (modified) flang/test/Driver/linker-flags.f90 (+1-1)
• (modified) flang/tools/flang-driver/driver.cpp (+2)

diff --git a/flang/CMakeLists.txt b/flang/CMakeLists.txt
index 0bfada476348a..6cbe6d4ed6a3e 100644
--- a/flang/CMakeLists.txt
+++ b/flang/CMakeLists.txt
@@ -317,7 +317,7 @@ if (NOT ENABLE_LINKER_BUILD_ID)
   set(ENABLE_LINKER_BUILD_ID OFF CACHE BOOL "pass --build-id to ld")
 endif()
 
-set(FLANG_DEFAULT_LINKER "" CACHE STRING
+set(FLANG_DEFAULT_LINKER ${CLANG_DEFAULT_LINKER} CACHE STRING
   "Default linker to use (linker name or absolute path, empty for platform default)")
 
 set(FLANG_DEFAULT_RTLIB "" CACHE STRING
diff --git a/flang/include/flang/Config/config.h.cmake b/flang/include/flang/Config/config.h.cmake
index fd34d3f403631..92fbd14c3d6db 100644
--- a/flang/include/flang/Config/config.h.cmake
+++ b/flang/include/flang/Config/config.h.cmake
@@ -1,10 +1,10 @@
-#===-- include/flang/Config/config.h.cmake ---------------------------------===#
-#
-# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-# See https://llvm.org/LICENSE.txt for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-#
-#===------------------------------------------------------------------------===#
+//===-- include/flang/Config/config.h.cmake -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
 
 /* This generated file is for internal use. Do not include it from headers. */
 
@@ -16,6 +16,8 @@
 
 #define FLANG_VERSION            "${FLANG_VERSION}"
 
+#define FLANG_DEFAULT_LINKER     "${FLANG_DEFAULT_LINKER}"
+
 #endif
 
 
diff --git a/flang/test/Driver/linker-flags.f90 b/flang/test/Driver/linker-flags.f90
index ad48ea1b9e9b1..2b56fdfb8da05 100644
--- a/flang/test/Driver/linker-flags.f90
+++ b/flang/test/Driver/linker-flags.f90
@@ -77,7 +77,7 @@
 ! MINGW-SAME: -lflang_rt.runtime
 ! MINGW-STATIC-FLANGRT: "{{.*}}{{\\|/}}libflang_rt.runtime.a"
 
-! NOTE: This also matches lld-link (when CLANG_DEFAULT_LINKER=lld) and
+! NOTE: This also matches lld-link (when FLANG_DEFAULT_LINKER=lld) and
 !       any .exe suffix that is added when resolving to the full path of
 !       (lld-)link.exe on Windows platforms. The suffix may not be added
 !       when the executable is not found or on non-Windows platforms.
diff --git a/flang/tools/flang-driver/driver.cpp b/flang/tools/flang-driver/driver.cpp
index 3a2dffc66428f..b1e02383cd33d 100644
--- a/flang/tools/flang-driver/driver.cpp
+++ b/flang/tools/flang-driver/driver.cpp
@@ -16,6 +16,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Driver/Driver.h"
+#include "flang/Config/config.h"
 #include "flang/Frontend/CompilerInvocation.h"
 #include "flang/Frontend/TextDiagnosticPrinter.h"
 #include "clang/Basic/Diagnostic.h"
@@ -138,6 +139,7 @@ int main(int argc, const char **argv) {
                                   llvm::sys::getDefaultTargetTriple(), diags,
                                   "flang LLVM compiler");
   theDriver.setTargetAndMode(targetandMode);
+  theDriver.setPreferredLinker(FLANG_DEFAULT_LINKER);
 #ifdef FLANG_RUNTIME_F128_MATH_LIB
   theDriver.setFlangF128MathLibrary(FLANG_RUNTIME_F128_MATH_LIB);
 #endif

[parabola94]

@tarunprabhu @kkwli Could you review this PR?

[tarunprabhu]

Thanks. Still LGTM. :-)

Please wait a while before merging to give others a chance to take a look.

[parabola94]

@kkwli Ping.
I would like to merge it next week because Tarun has already approved this PR.

[tarunprabhu]

@parabola94

Do you have permissions to add reviewers to your PR? If so, it generally works better to explicitly request reviews from people that way.

[parabola94]

@parabola94

Do you have permissions to add reviewers to your PR? If so, it generally works better to explicitly request reviews from people that way.

Unfortunately, I do not have permissions to do so. Thank you for your help!

[kkwli]

Sorry for the delay.

LG. Thanks.