[WoA][MSVC] Use default linker setting in MSVC-compatible driver [take 2]

[maxim-kuvyrkov]

Summary

At the moment "link.exe" is hard-coded as default linker in MSVC.cpp,
so there's no way to use LLD as default linker for MSVC driver.

This patch adds checking of CLANG_DEFAULT_LINKER to MSVC.cpp and
updates unit-tests that expect link.exe linker to explicitly select it
via -fuse-ld=link, so that buildbots and other builds that set
-DCLANG_DEFAULT_LINKER=foobar don't fail these tests.

This is a squash of

• https://reviews.llvm.org/D98493 (MSVC.cpp change) and
• https://reviews.llvm.org/D98862 (unit-tests change)

[maxim-kuvyrkov]

NFC: Make clang-format happy

[maxim-kuvyrkov]

This was reviewed in https://reviews.llvm.org/D98493 and https://reviews.llvm.org/D98862.

[maxim-kuvyrkov]

@tstellar

Hi Tom,

This has passed buildbots, so I'll cherry-pick this to release/12.x to fix https://bugs.llvm.org/show_bug.cgi?id=49624

clang/lib/Driver/ToolChains/MSVC.cpp

 //===-- MSVC.cpp - MSVC ToolChain Implementations -------------------------===//
 //
 // 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 "MSVC.h"
 #include "CommonArgs.h"
 #include "Darwin.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/Version.h"
+#include "clang/Config/config.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Options.h"
 #include "clang/Driver/SanitizerArgs.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Option/Arg.h"
void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   TC.addProfileRTLibs(Args, CmdArgs);
 
   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
   // linker, we need to use a special search algorithm.
   llvm::SmallString<128> linkPath;
-  StringRef Linker = Args.getLastArgValue(options::OPT_fuse_ld_EQ, "link");
+  StringRef Linker
+    = Args.getLastArgValue(options::OPT_fuse_ld_EQ, CLANG_DEFAULT_LINKER);
+  if (Linker.empty())
+    Linker = "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
     // from the program PATH, because other environments like GnuWin32 install
     // their own link.exe which may come first.
     linkPath = FindVisualStudioExecutable(TC, "link.exe");

clang/test/Driver/Xlinker-args.c

 // RUN:   -Wl,two,--no-demangle,three -Xlinker four -z five -r %s 2> %t
 // RUN: FileCheck -check-prefix=LINUX < %t %s
 //
 // DARWIN-NOT: --no-demangle
 // DARWIN: "one" "two" "three" "four" "-z" "five" "-r"
 // LINUX: "--no-demangle" "-e" "_start" "one" "two" "three" "four" "-z" "five" "-r" {{.*}} "-T" "a.lds"
 
 // Check that we forward '-Xlinker' and '-Wl,' on Windows.
-// RUN: %clang -target i686-pc-win32 -### \
+// RUN: %clang -target i686-pc-win32 -fuse-ld=link -### \
 // RUN:   -Xlinker one -Wl,two %s 2>&1 | \
 // RUN:   FileCheck -check-prefix=WIN %s
 // WIN: link.exe
 // WIN: "one"
 // WIN: "two"

clang/test/Driver/cl-inputs.c

 // TClib-NOT: cl-test.lib
 
 // RUN: not %clang_cl - 2>&1 | FileCheck -check-prefix=STDIN %s
 // STDIN: error: use /Tc or /Tp
 
 // RUN: %clang_cl -### /Tc - 2>&1 | FileCheck -check-prefix=STDINTc %s
 // STDINTc: "-x" "c"
 
-// RUN: env LIB=%S/Inputs/cl-libs %clang_cl -### -- %s cl-test.lib 2>&1 | FileCheck -check-prefix=LIBINPUT %s
+// RUN: env LIB=%S/Inputs/cl-libs %clang_cl -fuse-ld=link -### -- %s cl-test.lib 2>&1 | FileCheck -check-prefix=LIBINPUT %s
 // LIBINPUT: link.exe"
 // LIBINPUT: "cl-test.lib"
 
-// RUN: env LIB=%S/Inputs/cl-libs %clang_cl -### -- %s cl-test2.lib 2>&1 | FileCheck -check-prefix=LIBINPUT2 %s
+// RUN: env LIB=%S/Inputs/cl-libs %clang_cl -fuse-ld=link -### -- %s cl-test2.lib 2>&1 | FileCheck -check-prefix=LIBINPUT2 %s
 // LIBINPUT2: error: no such file or directory: 'cl-test2.lib'
 // LIBINPUT2: link.exe"
 // LIBINPUT2-NOT: "cl-test2.lib"
 
-// RUN: %clang_cl -### -- %s /nonexisting.lib 2>&1 | FileCheck -check-prefix=LIBINPUT3 %s
+// RUN: %clang_cl -fuse-ld=link -### -- %s /nonexisting.lib 2>&1 | FileCheck -check-prefix=LIBINPUT3 %s
 // LIBINPUT3: error: no such file or directory: '/nonexisting.lib'
 // LIBINPUT3: link.exe"
 // LIBINPUT3-NOT: "/nonexisting.lib"
 
 void f();

clang/test/Driver/cl-link-at-file.c

 // PR17239 - The /link option, when inside a response file, should only extend
 // until the end of the response file (and not the entire command line)
 
 // Note: %s must be preceded by -- or bound to another option, otherwise it may
 // be interpreted as a command-line option, e.g. on Mac where %s is commonly
 // under /Users.
 
 // RUN: echo /link bar.lib baz.lib > %t.args
 // RUN: touch %t.obj
-// RUN: %clang_cl -### @%t.args -- %t.obj 2>&1 | FileCheck %s -check-prefix=ARGS
+// RUN: %clang_cl -fuse-ld=link -### @%t.args -- %t.obj 2>&1 | FileCheck %s -check-prefix=ARGS
 // If the "/link" option captures all remaining args beyond its response file,
 // it will also capture "--" and our input argument. In this case, Clang will
 // be clueless and will emit "argument unused" warnings. If PR17239 is properly
 // fixed, this should not happen because the "/link" option is restricted to
 // consume only remaining args in its response file.
 // ARGS-NOT: argument unused during compilation
 // Identify the linker command
 // ARGS: link.exe

clang/test/Driver/cl-link.c

 // Note: %s must be preceded by -- or bound to another option, otherwise it may
 // be interpreted as a command-line option, e.g. on Mac where %s is commonly
 // under /Users.
 
-// RUN: %clang_cl /Tc%s -### /link foo bar baz 2>&1 | FileCheck --check-prefix=LINK %s
-// RUN: %clang_cl /Tc%s -### /linkfoo bar baz 2>&1 | FileCheck --check-prefix=LINK %s
+// RUN: %clang_cl /Tc%s -fuse-ld=link -### /link foo bar baz 2>&1 | FileCheck --check-prefix=LINK %s
+// RUN: %clang_cl /Tc%s -fuse-ld=link -### /linkfoo bar baz 2>&1 | FileCheck --check-prefix=LINK %s
 // LINK: link.exe
 // LINK: "foo"
 // LINK: "bar"
 // LINK: "baz"
 
-// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /Tc%s -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN %s
+// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /Tc%s -fuse-ld=link -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN %s
 // ASAN: link.exe
 // ASAN: "-debug"
 // ASAN: "-incremental:no"
 // ASAN: "{{[^"]*}}clang_rt.asan-i386.lib"
 // ASAN: "-wholearchive:{{.*}}clang_rt.asan-i386.lib"
 // ASAN: "{{[^"]*}}clang_rt.asan_cxx-i386.lib"
 // ASAN: "-wholearchive:{{.*}}clang_rt.asan_cxx-i386.lib"
 // ASAN: "{{.*}}cl-link{{.*}}.obj"
 
-// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /MD /Tc%s -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN-MD %s
+// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /MD /Tc%s -fuse-ld=link -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN-MD %s
 // ASAN-MD: link.exe
 // ASAN-MD: "-debug"
 // ASAN-MD: "-incremental:no"
 // ASAN-MD: "{{.*}}clang_rt.asan_dynamic-i386.lib"
 // ASAN-MD: "{{[^"]*}}clang_rt.asan_dynamic_runtime_thunk-i386.lib"
 // ASAN-MD: "-include:___asan_seh_interceptor"
 // ASAN-MD: "-wholearchive:{{.*}}clang_rt.asan_dynamic_runtime_thunk-i386.lib"
 // ASAN-MD: "{{.*}}cl-link{{.*}}.obj"
 
-// RUN: %clang_cl /LD -### /Tc%s 2>&1 | FileCheck --check-prefix=DLL %s
-// RUN: %clang_cl /LDd -### /Tc%s 2>&1 | FileCheck --check-prefix=DLL %s
+// RUN: %clang_cl /LD -fuse-ld=link -### /Tc%s 2>&1 | FileCheck --check-prefix=DLL %s
+// RUN: %clang_cl /LDd -fuse-ld=link -### /Tc%s 2>&1 | FileCheck --check-prefix=DLL %s
 // DLL: link.exe
 // "-dll"
 
-// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /LD /Tc%s -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN-DLL %s
-// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /LDd /Tc%s -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN-DLL %s
+// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /LD /Tc%s -fuse-ld=link -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN-DLL %s
+// RUN: %clang_cl -m32 -arch:IA32 --target=i386-pc-win32 /LDd /Tc%s -fuse-ld=link -### -fsanitize=address 2>&1 | FileCheck --check-prefix=ASAN-DLL %s
 // ASAN-DLL: link.exe
 // ASAN-DLL: "-dll"
 // ASAN-DLL: "-debug"
 // ASAN-DLL: "-incremental:no"
 // ASAN-DLL: "{{.*}}clang_rt.asan_dll_thunk-i386.lib"
 // ASAN-DLL: "{{.*}}cl-link{{.*}}.obj"
 
-// RUN: %clang_cl /Zi /Tc%s -### 2>&1 | FileCheck --check-prefix=DEBUG %s
+// RUN: %clang_cl /Zi /Tc%s -fuse-ld=link -### 2>&1 | FileCheck --check-prefix=DEBUG %s
 // DEBUG: link.exe
 // DEBUG: "-debug"
 
 // PR27234
-// RUN: %clang_cl /Tc%s nonexistent.obj -### /link /libpath:somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
-// RUN: %clang_cl /Tc%s nonexistent.lib -### /link /libpath:somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
+// RUN: %clang_cl /Tc%s nonexistent.obj -fuse-ld=link -### /link /libpath:somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
+// RUN: %clang_cl /Tc%s nonexistent.lib -fuse-ld=link -### /link /libpath:somepath 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
 // NONEXISTENT-NOT: no such file
 // NONEXISTENT: link.exe
 // NONEXISTENT: "/libpath:somepath"
 // NONEXISTENT: nonexistent
 
 // RUN: %clang_cl /Tc%s -fuse-ld=lld -### 2>&1 | FileCheck --check-prefix=USE_LLD %s
 // USE_LLD: lld-link

clang/test/Driver/msvc-link.c

-// RUN: %clang -target i686-pc-windows-msvc -### %s 2>&1 | FileCheck --check-prefix=BASIC %s
+// RUN: %clang -target i686-pc-windows-msvc -fuse-ld=link -### %s 2>&1 | FileCheck --check-prefix=BASIC %s
 // BASIC: link.exe"
 // BASIC: "-out:a.exe"
 // BASIC: "-defaultlib:libcmt"
 // BASIC: "-defaultlib:oldnames"
 // BASIC: "-nologo"
 // BASIC-NOT: "-Brepro"
 
-// RUN: %clang -target i686-pc-windows-msvc -shared -o a.dll -### %s 2>&1 | FileCheck --check-prefix=DLL %s
+// RUN: %clang -target i686-pc-windows-msvc -shared -o a.dll -fuse-ld=link -### %s 2>&1 | FileCheck --check-prefix=DLL %s
 // DLL: link.exe"
 // DLL: "-out:a.dll"
 // DLL: "-defaultlib:libcmt"
 // DLL: "-defaultlib:oldnames"
 // DLL: "-nologo"
 // DLL: "-dll"
 
 // RUN: %clang -target i686-pc-windows-msvc -L/var/empty -L/usr/lib -### %s 2>&1 | FileCheck --check-prefix LIBPATH %s
 // LIBPATH: "-libpath:/var/empty"
 // LIBPATH: "-libpath:/usr/lib"
 // LIBPATH: "-nologo"
 
-// RUN: %clang_cl /Brepro -### -- %s 2>&1 | FileCheck --check-prefix=REPRO %s
+// RUN: %clang_cl /Brepro -fuse-ld=link -### -- %s 2>&1 | FileCheck --check-prefix=REPRO %s
 // REPRO: link.exe"
 // REPRO: "-out:msvc-link.exe"
 // REPRO: "-nologo"
 // REPRO: "-Brepro"
 
-// RUN: %clang_cl /Brepro- -### -- %s 2>&1 | FileCheck --check-prefix=NOREPRO %s
+// RUN: %clang_cl /Brepro- -fuse-ld=link -### -- %s 2>&1 | FileCheck --check-prefix=NOREPRO %s
 // NOREPRO: link.exe"
 // NOREPRO: "-out:msvc-link.exe"
 // NOREPRO: "-nologo"
 // NOREPRO-NOT: "-Brepro"

clang/test/OpenMP/linking.c

 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -fopenmp -fopenmp=libgomp -target x86_64-unknown-linux \
 // RUN:     -rtlib=platform \
 // RUN:   | FileCheck --check-prefix=CHECK-LD-OVERRIDE-64 %s
 // CHECK-LD-OVERRIDE-64: "{{.*}}ld{{(.exe)?}}"
 // CHECK-LD-OVERRIDE-64: "-lgomp" "-lrt"
 // CHECK-LD-OVERRIDE-64: "-lpthread" "-lc"
 //
-// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN: %clang -no-canonical-prefixes -fuse-ld=link %s -### -o %t.o 2>&1 \
 // RUN:     -fopenmp=libomp -target x86_64-msvc-win32 -rtlib=platform \
 // RUN:   | FileCheck --check-prefix=CHECK-MSVC-LINK-64 %s
 // CHECK-MSVC-LINK-64: link.exe
 // CHECK-MSVC-LINK-64-SAME: -nodefaultlib:vcomp.lib
 // CHECK-MSVC-LINK-64-SAME: -nodefaultlib:vcompd.lib
 // CHECK-MSVC-LINK-64-SAME: -libpath:{{.+}}/../lib
 // CHECK-MSVC-LINK-64-SAME: -defaultlib:libomp.lib
 
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 -fopenmp-simd -target x86_64-msvc-win32 -rtlib=platform | FileCheck --check-prefix SIMD-ONLY11 %s
 // SIMD-ONLY11-NOT: libiomp
 // SIMD-ONLY11-NOT: libomp
 // SIMD-ONLY11-NOT: libgomp
 //
-// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+// RUN: %clang -no-canonical-prefixes %s -fuse-ld=link -### -o %t.o 2>&1 \
 // RUN:     -fopenmp=libiomp5 -target x86_64-msvc-win32 -rtlib=platform \
 // RUN:   | FileCheck --check-prefix=CHECK-MSVC-ILINK-64 %s
 
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 -fopenmp-simd -target x86_64-msvc-win32 -rtlib=platform | FileCheck --check-prefix SIMD-ONLY11 %s
 // SIMD-ONLY11-NOT: libiomp
 // SIMD-ONLY11-NOT: libomp
 // SIMD-ONLY11-NOT: libgomp
 // CHECK-MSVC-ILINK-64: link.exe
 // CHECK-MSVC-ILINK-64-SAME: -nodefaultlib:vcomp.lib
 // CHECK-MSVC-ILINK-64-SAME: -nodefaultlib:vcompd.lib
 // CHECK-MSVC-ILINK-64-SAME: -libpath:{{.+}}/../lib
 // CHECK-MSVC-ILINK-64-SAME: -defaultlib:libiomp5md.lib
 //