clang/win: Add a flag to disable default-linking of compiler-rt libraries (#89642)

For ASan, users already manually have to pass in the path to the lib,
and for other libraries they have to pass in the path to the libpath.

With LLVM's unreliable name of the lib (due to
LLVM_ENABLE_PER_TARGET_RUNTIME_DIR confusion and whatnot), it's useful
to be able to opt in to just explicitly passing the paths to the libs
everywhere.

Follow-up of sorts to https://reviews.llvm.org/D65543, and to #87866.

6 files changed, 41 insertions, 4 deletions

diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index c464bc3a69ad..8df40566fcba 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -4921,6 +4921,9 @@ directory. Using the example installation above, this would mean passing
 If the user links the program with the ``clang`` or ``clang-cl`` drivers, the
 driver will pass this flag for them.
 
+The auto-linking can be disabled with -fno-rtlib-defaultlib. If that flag is
+used, pass the complete flag to required libraries as described for ASan below.
+
 If the linker cannot find the appropriate library, it will emit an error like
 this::
 
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 3c55aceecdde..922bda721dc7 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5508,6 +5508,14 @@ def fno_rtlib_add_rpath: Flag<["-"], "fno-rtlib-add-rpath">,
   Visibility<[ClangOption, FlangOption]>,
   HelpText<"Do not add -rpath with architecture-specific resource directory to the linker flags. "
   "When --hip-link is specified, do not add -rpath with HIP runtime library directory to the linker flags">;
+def frtlib_defaultlib : Flag<["-"], "frtlib-defaultlib">,
+                      Visibility<[ClangOption, CLOption]>,
+                      Group<f_Group>,
+                      HelpText<"On Windows, emit /defaultlib: directives to link compiler-rt libraries (default)">;
+def fno_rtlib_defaultlib : Flag<["-"], "fno-rtlib-defaultlib">,
+                      Visibility<[ClangOption, CLOption]>,
+                      Group<f_Group>,
+                      HelpText<"On Windows, do not emit /defaultlib: directives to link compiler-rt libraries">;
 def offload_add_rpath: Flag<["--"], "offload-add-rpath">,
   Flags<[NoArgumentUnused]>,
   Alias<frtlib_add_rpath>;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 8bfe9f02a091..6a4f2548c0bf 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -1192,7 +1192,9 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
                           BinaryMetadataIgnorelistFiles);
   }
 
-  if (TC.getTriple().isOSWindows() && needsUbsanRt()) {
+  if (TC.getTriple().isOSWindows() && needsUbsanRt() &&
+      Args.hasFlag(options::OPT_frtlib_defaultlib,
+                   options::OPT_fno_rtlib_defaultlib, true)) {
     // Instruct the code generator to embed linker directives in the object file
     // that cause the required runtime libraries to be linked.
     CmdArgs.push_back(
@@ -1203,7 +1205,9 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
           "--dependent-lib=" +
           TC.getCompilerRTBasename(Args, "ubsan_standalone_cxx")));
   }
-  if (TC.getTriple().isOSWindows() && needsStatsRt()) {
+  if (TC.getTriple().isOSWindows() && needsStatsRt() &&
+      Args.hasFlag(options::OPT_frtlib_defaultlib,
+                   options::OPT_fno_rtlib_defaultlib, true)) {
     CmdArgs.push_back(Args.MakeArgString(
         "--dependent-lib=" + TC.getCompilerRTBasename(Args, "stats_client")));
 
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 5894a48e0e37..e7ccf9a23e7e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -637,7 +637,9 @@ static void addPGOAndCoverageFlags(const ToolChain &TC, Compilation &C,
                                            ProfileGenerateArg->getValue()));
     // The default is to use Clang Instrumentation.
     CmdArgs.push_back("-fprofile-instrument=clang");
-    if (TC.getTriple().isWindowsMSVCEnvironment()) {
+    if (TC.getTriple().isWindowsMSVCEnvironment() &&
+        Args.hasFlag(options::OPT_frtlib_defaultlib,
+                     options::OPT_fno_rtlib_defaultlib, true)) {
       // Add dependent lib for clang_rt.profile
       CmdArgs.push_back(Args.MakeArgString(
           "--dependent-lib=" + TC.getCompilerRTBasename(Args, "profile")));
@@ -656,7 +658,9 @@ static void addPGOAndCoverageFlags(const ToolChain &TC, Compilation &C,
     CmdArgs.push_back("-fprofile-instrument=csllvm");
   }
   if (PGOGenArg) {
-    if (TC.getTriple().isWindowsMSVCEnvironment()) {
+    if (TC.getTriple().isWindowsMSVCEnvironment() &&
+        Args.hasFlag(options::OPT_frtlib_defaultlib,
+                     options::OPT_fno_rtlib_defaultlib, true)) {
       // Add dependent lib for clang_rt.profile
       CmdArgs.push_back(Args.MakeArgString(
           "--dependent-lib=" + TC.getCompilerRTBasename(Args, "profile")));
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 7731300ae9f5..75f49deca065 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -70,12 +70,16 @@
 // fsanitize_address: -fsanitize=address
 
 // RUN: %clang_cl -### /FA -fprofile-instr-generate -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-INSTR-GENERATE %s
+// RUN: %clang_cl -### /FA -fprofile-instr-generate -fno-rtlib-defaultlib -frtlib-defaultlib -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-INSTR-GENERATE %s
 // RUN: %clang_cl -### /FA -fprofile-instr-generate=/tmp/somefile.profraw -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-INSTR-GENERATE-FILE %s
 // RUN: %clang_cl -### /FAcsu -fprofile-instr-generate -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-INSTR-GENERATE %s
 // RUN: %clang_cl -### /FAcsu -fprofile-instr-generate=/tmp/somefile.profraw -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-INSTR-GENERATE-FILE %s
 // CHECK-PROFILE-INSTR-GENERATE: "-fprofile-instrument=clang" "--dependent-lib=clang_rt.profile{{[^"]*}}.lib"
 // CHECK-PROFILE-INSTR-GENERATE-FILE: "-fprofile-instrument-path=/tmp/somefile.profraw"
 
+// RUN: %clang_cl -### /FA -fprofile-instr-generate -fno-rtlib-defaultlib -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-INSTR-GENERATE-NODEF %s
+// CHECK-PROFILE-INSTR-GENERATE-NODEF-NOT: "--dependent-lib=clang_rt.profile{{[^"]*}}.lib"
+
 // RUN: %clang_cl -### /FA -fprofile-generate -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-GENERATE %s
 // RUN: %clang_cl -### /FAcsu -fprofile-generate -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-GENERATE %s
 // CHECK-PROFILE-GENERATE: "-fprofile-instrument=llvm" "--dependent-lib=clang_rt.profile{{[^"]*}}.lib"
diff --git a/clang/test/Driver/sanitizer-ld.c b/clang/test/Driver/sanitizer-ld.c
index f5657e47626e..7289d09697b4 100644
--- a/clang/test/Driver/sanitizer-ld.c
+++ b/clang/test/Driver/sanitizer-ld.c
@@ -802,10 +802,24 @@
 // RUN:     --target=i686-pc-windows \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-CFI-STATS-WIN32 %s
+// RUN: not %clang -fsanitize=cfi -fsanitize-stats -### %s 2>&1 \
+// RUN:     --target=i686-pc-windows \
+// RUN:     -fno-rtlib-defaultlib \
+// RUN:     -frtlib-defaultlib \
+// RUN:     --sysroot=%S/Inputs/basic_linux_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-CFI-STATS-WIN32 %s
 // CHECK-CFI-STATS-WIN32: "--dependent-lib=clang_rt.stats_client{{(-i386)?}}.lib"
 // CHECK-CFI-STATS-WIN32: "--dependent-lib=clang_rt.stats{{(-i386)?}}.lib"
 // CHECK-CFI-STATS-WIN32: "--linker-option=/include:___sanitizer_stats_register"
 
+// RUN: not %clang -fsanitize=cfi -fsanitize-stats -### %s 2>&1 \
+// RUN:     --target=i686-pc-windows \
+// RUN:     -fno-rtlib-defaultlib \
+// RUN:     --sysroot=%S/Inputs/basic_linux_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-CFI-STATS-WIN32-NODEF %s
+// CHECK-CFI-STATS-WIN32-NODEF-NOT: "--dependent-lib=clang_rt.stats_client{{(-i386)?}}.lib"
+// CHECK-CFI-STATS-WIN32-NODEF-NOT: "--dependent-lib=clang_rt.stats{{(-i386)?}}.lib"
+
 // RUN: %clang -### %s 2>&1 \
 // RUN:     --target=arm-linux-androideabi -fuse-ld=ld -fsanitize=safe-stack \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree \