[compiler-rt] Include -lm when using compiler-rt, due to dependencies in some __div methods.

[rupprecht]

Summary

Some methods in compiler-rt builtins (divdc3, divsc3, and __divxc3, and maybe others) have dependencies on libm. Therefore building with -rtlib=compiler-rt is completely broken if those symbols are used and users don't include -lm themselves.

Fixes PR32279 and PR28652.

[efriedma]

Probably compiler-rt should be fixed so it doesn't need libm, rather than fixing clang to add -lm. (All the functions it currently uses can be implemented with simple bit manipulation.)

[rupprecht]

Thanks Eli, I'll see how hard it is to remove those calls to logb/logbf (those seem to be the only ones causing link errors) and revert this change if that's possible.

lib/Driver/ToolChains/CommonArgs.cpp

 void tools::AddRunTimeLibs(const ToolChain &TC, const Driver &D,
                            ArgStringList &CmdArgs, const ArgList &Args) {
   // Make use of compiler-rt if --rtlib option is used
   ToolChain::RuntimeLibType RLT = TC.GetRuntimeLibType(Args);
 
   switch (RLT) {
   case ToolChain::RLT_CompilerRT:
     CmdArgs.push_back(TC.getCompilerRTArgString(Args, "builtins"));
+    // Some methods such as __divdc3, __divsc3, and __divxc3 rely on libm
+    CmdArgs.push_back("-lm");
     break;
   case ToolChain::RLT_Libgcc:
     // Make sure libgcc is not used under MSVC environment by default
     if (TC.getTriple().isKnownWindowsMSVCEnvironment()) {
       // Issue error diagnostic if libgcc is explicitly specified
       // through command line as --rtlib option argument.
       if (Args.hasArg(options::OPT_rtlib_EQ)) {
         TC.getDriver().Diag(diag::err_drv_unsupported_rtlib_for_platform)

test/Driver/linux-ld.c

 // CHECK-LD-RT: "-dynamic-linker"
 // CHECK-LD-RT: "{{.*}}/usr/lib/gcc/x86_64-unknown-linux/4.6.0{{/|\\\\}}crtbegin.o"
 // CHECK-LD-RT: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0"
 // CHECK-LD-RT: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../../../x86_64-unknown-linux/lib"
 // CHECK-LD-RT: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-unknown-linux/4.6.0/../../.."
 // CHECK-LD-RT: "-L[[SYSROOT]]/lib"
 // CHECK-LD-RT: "-L[[SYSROOT]]/usr/lib"
 // CHECK-LD-RT: libclang_rt.builtins-x86_64.a"
+// CHECK-LD-RT: "-lm"
 // CHECK-LD-RT: "-lc"
 // CHECK-LD-RT: libclang_rt.builtins-x86_64.a"
+// CHECK-LD-RT: "-lm"
 //
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=i686-unknown-linux \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:     --rtlib=compiler-rt \
 // RUN:   | FileCheck --check-prefix=CHECK-LD-RT-I686 %s
 // CHECK-LD-RT-I686-NOT: warning:
 // CHECK-LD-RT-I686: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
 // CHECK-LD-RT-I686: "--eh-frame-hdr"
 // CHECK-LD-RT-I686: "-m" "elf_i386"
 // CHECK-LD-RT-I686: "-dynamic-linker"
 // CHECK-LD-RT-I686: "{{.*}}/usr/lib/gcc/i686-unknown-linux/4.6.0{{/|\\\\}}crtbegin.o"
 // CHECK-LD-RT-I686: "-L[[SYSROOT]]/usr/lib/gcc/i686-unknown-linux/4.6.0"
 // CHECK-LD-RT-I686: "-L[[SYSROOT]]/usr/lib/gcc/i686-unknown-linux/4.6.0/../../../../i686-unknown-linux/lib"
 // CHECK-LD-RT-I686: "-L[[SYSROOT]]/usr/lib/gcc/i686-unknown-linux/4.6.0/../../.."
 // CHECK-LD-RT-I686: "-L[[SYSROOT]]/lib"
 // CHECK-LD-RT-I686: "-L[[SYSROOT]]/usr/lib"
 // CHECK-LD-RT-I686: libclang_rt.builtins-i386.a"
+// CHECK-LD-RT-I686: "-lm"
 // CHECK-LD-RT-I686: "-lc"
 // CHECK-LD-RT-I686: libclang_rt.builtins-i386.a"
+// CHECK-LD-RT-I686: "-lm"
 //
 // 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:     --rtlib=compiler-rt \
 // RUN:   | FileCheck --check-prefix=CHECK-LD-RT-ANDROID %s
 // CHECK-LD-RT-ANDROID-NOT: warning:
 // CHECK-LD-RT-ANDROID: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"
 // CHECK-LD-RT-ANDROID: "--eh-frame-hdr"
 // CHECK-LD-RT-ANDROID: "-m" "armelf_linux_eabi"
 // CHECK-LD-RT-ANDROID: "-dynamic-linker"
 // CHECK-LD-RT-ANDROID: libclang_rt.builtins-arm-android.a"
+// CHECK-LD-RT-ANDROID: "-lm"
 // CHECK-LD-RT-ANDROID: "-lc"
 // CHECK-LD-RT-ANDROID: libclang_rt.builtins-arm-android.a"
+// CHECK-LD-RT-ANDROID: "-lm"
 //
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     --target=x86_64-unknown-linux -rtlib=platform \
 // RUN:     --gcc-toolchain="" \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:     --rtlib=libgcc \
 // RUN:   | FileCheck --check-prefix=CHECK-LD-GCC %s
 // CHECK-LD-GCC-NOT: warning:

test/Driver/wasm-toolchain.c

 // A basic clang -cc1 command-line. WebAssembly is somewhat special in
 // enabling -fvisibility=hidden by default.
 
 // RUN: %clang %s -### -no-canonical-prefixes -target wasm32-unknown-unknown 2>&1 | FileCheck -check-prefix=CC1 %s
 // CC1: clang{{.*}} "-cc1" "-triple" "wasm32-unknown-unknown" {{.*}} "-fvisibility" "hidden" {{.*}}
 
 // Ditto, but ensure that a user -fvisibility=default disables the default
 // -fvisibility=hidden.
 
 // RUN: %clang %s -### -target wasm32-unknown-unknown -fvisibility=default 2>&1 | FileCheck -check-prefix=FVISIBILITY_DEFAULT %s
 // FVISIBILITY_DEFAULT-NOT: hidden
 
 // A basic C link command-line.
 
 // RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=/foo %s 2>&1 | FileCheck -check-prefix=LINK %s
 // LINK: clang{{.*}}" "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+// LINK: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-lm" "-o" "a.out"
 
 // A basic C link command-line with optimization.
 
 // RUN: %clang -### -O2 -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=/foo %s 2>&1 | FileCheck -check-prefix=LINK_OPT %s
 // LINK_OPT: clang{{.*}}" "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK_OPT: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+// LINK_OPT: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-lm" "-o" "a.out"

test/Driver/wasm-toolchain.cpp

 // A basic clang -cc1 command-line. WebAssembly is somewhat special in
 // enabling -fvisibility=hidden by default.
 
 // RUN: %clangxx %s -### -no-canonical-prefixes -target wasm32-unknown-unknown 2>&1 | FileCheck -check-prefix=CC1 %s
 // CC1: clang{{.*}} "-cc1" "-triple" "wasm32-unknown-unknown" {{.*}} "-fvisibility" "hidden" {{.*}}
 
 // Ditto, but ensure that a user -fvisibility=default disables the default
 // -fvisibility=hidden.
 
 // RUN: %clangxx %s -### -target wasm32-unknown-unknown -fvisibility=default 2>&1 | FileCheck -check-prefix=FVISIBILITY_DEFAULT %s
 // FVISIBILITY_DEFAULT-NOT: hidden
 
 // A basic C++ link command-line.
 
 // RUN: %clangxx -### -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=/foo --stdlib=c++ %s 2>&1 | FileCheck -check-prefix=LINK %s
 // LINK: clang{{.*}}" "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc++" "-lc++abi" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+// LINK: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc++" "-lc++abi" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-lm" "-o" "a.out"
 
 // A basic C++ link command-line with optimization.
 
 // RUN: %clangxx -### -O2 -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=/foo %s --stdlib=c++ 2>&1 | FileCheck -check-prefix=LINK_OPT %s
 // LINK_OPT: clang{{.*}}" "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK_OPT: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc++" "-lc++abi" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-o" "a.out"
+// LINK_OPT: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "[[temp]]" "-lc++" "-lc++abi" "-lc" "{{.*[/\\]}}libclang_rt.builtins-wasm32.a" "-lm" "-o" "a.out"