[Android] Default to --rtlib=compiler-rt

[rprichard]

Summary

By default, the driver uses the compiler-rt builtins and links with
-l:libunwind.a.

Restore the previous behavior by passing --rtlib=libgcc.

[rprichard]

Adding glandium and thakis for Firefox and Chrome. e.g. I suspect this change would cause the same sort of breakage seen in D95166.

[rprichard]

Rebase this revision.

[smeenai]

Hilariously enough, this breaks building compiler-rt itself inside LLVM's runtime builds setup for us. The runtimes build setup builds clang and then uses the just-built clang to build compiler-rt. That build fails to link since my just-built clang doesn't have compiler-rt available, because it's currently trying to build compiler-rt itself. That's a bug in the compiler-rt build system, and I sent out https://lists.llvm.org/pipermail/llvm-dev/2021-March/149137.html to ask what we should do about it.

clang/lib/Driver/ToolChains/Linux.h

void addLibStdCxxIncludePaths(
       const llvm::opt::ArgList &DriverArgs,
       llvm::opt::ArgStringList &CC1Args) const override;
   void AddCudaIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                           llvm::opt::ArgStringList &CC1Args) const override;
   void AddHIPIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                          llvm::opt::ArgStringList &CC1Args) const override;
   void AddIAMCUIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                            llvm::opt::ArgStringList &CC1Args) const override;
+  RuntimeLibType GetDefaultRuntimeLibType() const override;
   CXXStdlibType GetDefaultCXXStdlibType() const override;
   bool
   IsAArch64OutlineAtomicsDefault(const llvm::opt::ArgList &Args) const override;
   bool isPIEDefault() const override;
   bool isNoExecStackDefault() const override;
   bool IsMathErrnoDefault() const override;
   SanitizerMask getSupportedSanitizers() const override;
   void addProfileRTLibs(const llvm::opt::ArgList &Args,

clang/lib/Driver/ToolChains/Linux.cpp

#endif
   // directory ('Dir' below) or the ResourceDir.
   if (StringRef(D.Dir).startswith(SysRoot))
     addPathIfExists(D, D.Dir + "/../lib", Paths);
 
   addPathIfExists(D, SysRoot + "/lib", Paths);
   addPathIfExists(D, SysRoot + "/usr/lib", Paths);
 }
 
+ToolChain::RuntimeLibType Linux::GetDefaultRuntimeLibType() const {
+  if (getTriple().isAndroid())
+    return ToolChain::RLT_CompilerRT;
+  return Generic_ELF::GetDefaultRuntimeLibType();
+}
+
 ToolChain::CXXStdlibType Linux::GetDefaultCXXStdlibType() const {
   if (getTriple().isAndroid())
     return ToolChain::CST_Libcxx;
   return ToolChain::CST_Libstdcxx;
 }
 
 bool Linux::HasNativeLLVMSupport() const { return true; }
 

clang/test/Driver/linux-ld.c

 // CHECK-CLANG-SHARED-LIBGCC-DYNAMIC: "-lgcc_s" "-lgcc"
 //
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=aarch64-linux-android -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-CLANG-ANDROID-NONE %s
 // CHECK-CLANG-ANDROID-NONE: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
-// CHECK-CLANG-ANDROID-NONE: "-lgcc" "-ldl" "-lc"
+// CHECK-CLANG-ANDROID-NONE: "-l:libunwind.a" "-ldl" "-lc"
 //
 // RUN: %clang -shared -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=aarch64-linux-android -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-CLANG-ANDROID-SHARED %s
 // CHECK-CLANG-ANDROID-SHARED: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
-// CHECK-CLANG-ANDROID-SHARED: "-lgcc" "-ldl" "-lc"
+// CHECK-CLANG-ANDROID-SHARED: "-l:libunwind.a" "-ldl" "-lc"
 //
 // RUN: %clang -static -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=aarch64-linux-android -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-CLANG-ANDROID-STATIC %s
 // CHECK-CLANG-ANDROID-STATIC: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
-// CHECK-CLANG-ANDROID-STATIC: "--start-group" "-lgcc" "-lc" "--end-group"
+// CHECK-CLANG-ANDROID-STATIC: "--start-group" "{{[^"]*}}{{/|\\\\}}libclang_rt.builtins-aarch64-android.a" "-l:libunwind.a" "-lc" "--end-group"
 //
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1      \
 // RUN:     --target=x86_64-unknown-linux -rtlib=platform \
 // RUN:     -static \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-LD-64-STATIC %s
 // CHECK-LD-64-STATIC-NOT: warning:

 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID %s
 // CHECK-ANDROID: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
 // CHECK-ANDROID: "-z" "now"
 // CHECK-ANDROID: "-z" "relro"
 // CHECK-ANDROID: "--enable-new-dtags"
 // CHECK-ANDROID: "{{.*}}{{/|\\\\}}crtbegin_dynamic.o"
 // CHECK-ANDROID: "-L[[SYSROOT]]/usr/lib"
-// CHECK-ANDROID-NOT: "gcc_s"
-// CHECK-ANDROID: "-lgcc"
+// CHECK-ANDROID-NOT: "-lgcc_s"
+// CHECK-ANDROID-NOT: "-lgcc"
+// CHECK-ANDROID: "-l:libunwind.a"
 // CHECK-ANDROID: "-ldl"
-// CHECK-ANDROID-NOT: "gcc_s"
+// CHECK-ANDROID-NOT: "-lgcc_s"
+// CHECK-ANDROID-NOT: "-lgcc"
 // CHECK-ANDROID: "{{.*}}{{/|\\\\}}crtend_android.o"
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=arm-linux-androideabi -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:     -shared \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-SO %s
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \

 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:     -shared \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-SO %s
 // CHECK-ANDROID-SO: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
 // CHECK-ANDROID-SO-NOT: "-Bsymbolic"
 // CHECK-ANDROID-SO: "{{.*}}{{/|\\\\}}crtbegin_so.o"
 // CHECK-ANDROID-SO: "-L[[SYSROOT]]/usr/lib"
-// CHECK-ANDROID-SO-NOT: "gcc_s"
-// CHECK-ANDROID-SO: "-lgcc"
+// CHECK-ANDROID-SO-NOT: "-lgcc_s"
+// CHECK-ANDROID-SO-NOT: "-lgcc"
+// CHECK-ANDROID-SO: "-l:libunwind.a"
 // CHECK-ANDROID-SO: "-ldl"
-// CHECK-ANDROID-SO-NOT: "gcc_s"
+// CHECK-ANDROID-SO-NOT: "-lgcc_s"
+// CHECK-ANDROID-SO-NOT: "-lgcc"
 // CHECK-ANDROID-SO: "{{.*}}{{/|\\\\}}crtend_so.o"
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=arm-linux-androideabi -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:     -static \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-STATIC %s
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \

 // RUN:     --target=x86_64-linux-android -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:     -static \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-STATIC %s
 // CHECK-ANDROID-STATIC: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
 // CHECK-ANDROID-STATIC: "{{.*}}{{/|\\\\}}crtbegin_static.o"
 // CHECK-ANDROID-STATIC: "-L[[SYSROOT]]/usr/lib"
-// CHECK-ANDROID-STATIC-NOT: "gcc_s"
-// CHECK-ANDROID-STATIC: "-lgcc"
+// CHECK-ANDROID-STATIC-NOT: "-lgcc_eh"
+// CHECK-ANDROID-STATIC-NOT: "-lgcc"
+// CHECK-ANDROID-STATIC: "-l:libunwind.a"
 // CHECK-ANDROID-STATIC-NOT: "-ldl"
-// CHECK-ANDROID-STATIC-NOT: "gcc_s"
+// CHECK-ANDROID-STATIC-NOT: "-lgcc_eh"
+// CHECK-ANDROID-STATIC-NOT: "-lgcc"
 // CHECK-ANDROID-STATIC: "{{.*}}{{/|\\\\}}crtend_android.o"
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=arm-linux-androideabi -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot  \
 // RUN:     -pie \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-PIE %s
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \

 // RUN:     --target=x86_64-linux-android -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:     -pie \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-PIE %s
 // CHECK-ANDROID-PIE: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
 // CHECK-ANDROID-PIE: "{{.*}}{{/|\\\\}}crtbegin_dynamic.o"
 // CHECK-ANDROID-PIE: "-L[[SYSROOT]]/usr/lib"
-// CHECK-ANDROID-PIE-NOT: "gcc_s"
-// CHECK-ANDROID-PIE: "-lgcc"
-// CHECK-ANDROID-PIE-NOT: "gcc_s"
+// CHECK-ANDROID-PIE-NOT: "-lgcc_s"
+// CHECK-ANDROID-PIE-NOT: "-lgcc"
+// CHECK-ANDROID-PIE: "-l:libunwind.a"
+// CHECK-ANDROID-PIE-NOT: "-lgcc_s"
+// CHECK-ANDROID-PIE-NOT: "-lgcc"
 // CHECK-ANDROID-PIE: "{{.*}}{{/|\\\\}}crtend_android.o"
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=arm-linux-androideabi \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree/sysroot \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-32 %s
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=arm-linux-android \