[RISCV][Driver] Add libm linking to `RISCVToolchain` for C++

[anton-afanasyev]

Summary

GCC automatically links math library by adding -lm to linker command
line, since C++ runtime libstdc++ requires libm, so add it to
RISCVToochain as well.

[anton-afanasyev]

Update summary

[jrtc27]

Commit subject/body should say C++ in it

[anton-afanasyev]

In D129065#3631052, @jrtc27 wrote:

Commit subject/body should say C++ in it

Sure, updated.

clang/lib/Driver/ToolChains/RISCVToolchain.cpp

void RISCV::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddAllArgs(CmdArgs,
                   {options::OPT_T_Group, options::OPT_e, options::OPT_s,
                    options::OPT_t, options::OPT_Z_Flag, options::OPT_r});
 
   // TODO: add C++ includes and libs if compiling C++.
 
   if (!Args.hasArg(options::OPT_nostdlib) &&
       !Args.hasArg(options::OPT_nodefaultlibs)) {
+    if (D.CCCIsCXX()) {
       if (ToolChain.ShouldLinkCXXStdlib(Args))
         ToolChain.AddCXXStdlibLibArgs(Args, CmdArgs);
+      CmdArgs.push_back("-lm");
+    }
     CmdArgs.push_back("--start-group");
     CmdArgs.push_back("-lc");
     CmdArgs.push_back("-lgloss");
     CmdArgs.push_back("--end-group");
     AddRunTimeLibs(ToolChain, ToolChain.getDriver(), CmdArgs, Args);
   }
 
   if (WantCRTs)

clang/test/Driver/riscv32-toolchain.c

 
 // CXX-RV32-BAREMETAL-ILP32: "-internal-isystem" "{{.*}}Inputs/basic_riscv32_tree/riscv32-unknown-elf/include/c++{{/|\\\\}}8.0.1"
 // CXX-RV32-BAREMETAL-ILP32: "{{.*}}Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}riscv32-unknown-elf-ld"
 // CXX-RV32-BAREMETAL-ILP32: "--sysroot={{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf"
 // CXX-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf/lib{{/|\\\\}}crt0.o"
 // CXX-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1{{/|\\\\}}crtbegin.o"
 // CXX-RV32-BAREMETAL-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1"
 // CXX-RV32-BAREMETAL-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf/lib"
-// CXX-RV32-BAREMETAL-ILP32: "-lstdc++" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// CXX-RV32-BAREMETAL-ILP32: "-lstdc++" "-lm" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // CXX-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clangxx -### %s -fuse-ld= \
 // RUN:   --target=riscv32-unknown-elf -stdlib=libstdc++ --rtlib=platform \
 // RUN:   --sysroot= \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv32_tree 2>&1 \
 // RUN:   | FileCheck -check-prefix=CXX-RV32-BAREMETAL-NOSYSROOT-ILP32 %s
 
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-internal-isystem" "{{.*}}Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}riscv32-unknown-linux-gnu/include/c++{{/|\\\\}}8.0.1"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "{{.*}}Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}riscv32-unknown-elf-ld"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}riscv32-unknown-linux-gnu/lib{{/|\\\\}}crt0.o"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1{{/|\\\\}}crtbegin.o"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}riscv32-unknown-linux-gnu/lib"
-// CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-lstdc++" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "-lstdc++" "-lm" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // CXX-RV32-BAREMETAL-NOSYSROOT-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-linux-gnu/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: env "PATH=" %clang -### %s -fuse-ld=ld -no-pie \
 // RUN:   --target=riscv32-unknown-linux-gnu --rtlib=platform -mabi=ilp32 \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_linux_sdk \
 // RUN:   --sysroot=%S/Inputs/multilib_riscv_linux_sdk/sysroot 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32-LINUX-MULTI-ILP32 %s
 

clang/test/Driver/riscv64-toolchain.c

 
 // CXX-RV64-BAREMETAL-LP64: "-internal-isystem" "{{.*}}Inputs/basic_riscv64_tree/riscv64-unknown-elf/include/c++{{/|\\\\}}8.0.1"
 // CXX-RV64-BAREMETAL-LP64: "{{.*}}Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}riscv64-unknown-elf-ld"
 // CXX-RV64-BAREMETAL-LP64: "--sysroot={{.*}}/Inputs/basic_riscv64_tree/riscv64-unknown-elf"
 // CXX-RV64-BAREMETAL-LP64: "{{.*}}/Inputs/basic_riscv64_tree/riscv64-unknown-elf/lib{{/|\\\\}}crt0.o"
 // CXX-RV64-BAREMETAL-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1{{/|\\\\}}crtbegin.o"
 // CXX-RV64-BAREMETAL-LP64: "-L{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1"
 // CXX-RV64-BAREMETAL-LP64: "-L{{.*}}/Inputs/basic_riscv64_tree/riscv64-unknown-elf/lib"
-// CXX-RV64-BAREMETAL-LP64: "-lstdc++" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// CXX-RV64-BAREMETAL-LP64: "-lstdc++" "-lm" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // CXX-RV64-BAREMETAL-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: env "PATH=" %clangxx -### %s -fuse-ld= \
 // RUN:   --target=riscv64-unknown-elf -stdlib=libstdc++ --rtlib=platform \
 // RUN:   --sysroot= \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv64_tree 2>&1 \
 // RUN:   | FileCheck -check-prefix=CXX-RV64-BAREMETAL-NOSYSROOT-LP64 %s
 
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-internal-isystem" "{{.*}}Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}riscv64-unknown-linux-gnu/include/c++{{/|\\\\}}8.0.1"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}riscv64-unknown-elf-ld"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}riscv64-unknown-linux-gnu/lib{{/|\\\\}}crt0.o"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1{{/|\\\\}}crtbegin.o"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-L{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-L{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1/../../..{{/|\\\\}}..{{/|\\\\}}riscv64-unknown-linux-gnu/lib"
-// CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-lstdc++" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "-lstdc++" "-lm" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-linux-gnu/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: env "PATH=" %clang -### %s -fuse-ld= -no-pie \
 // RUN:   --target=riscv64-unknown-linux-gnu --rtlib=platform -mabi=lp64 \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_linux_sdk \
 // RUN:   --sysroot=%S/Inputs/multilib_riscv_linux_sdk/sysroot 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV64-LINUX-MULTI-LP64 %s