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

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)

Reviewed By: maxim-kuvyrkov

Differential Revision: https://reviews.llvm.org/D98935

Author: maxim-kuvyrkov

clang/lib/Driver/ToolChains/MSVC.cpp

@@ -11,6 +11,7 @@
 #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"
@@ -577,7 +578,10 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   // 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";
 

clang/test/Driver/Xlinker-args.c

@@ -17,7 +17,7 @@
 // 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

clang/test/Driver/cl-inputs.c

@@ -50,16 +50,16 @@
 // 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"

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

@@ -7,7 +7,7 @@
 
 // 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

clang/test/Driver/cl-link.c

@@ -2,14 +2,14 @@
 // 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"
@@ -19,7 +19,7 @@
 // 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"
@@ -29,27 +29,27 @@
 // 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"

clang/test/Driver/msvc-link.c

@@ -1,12 +1,12 @@
-// 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"
@@ -19,13 +19,13 @@
 // 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"

clang/test/OpenMP/linking.c

@@ -81,7 +81,7 @@
 // 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
@@ -95,7 +95,7 @@
 // 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