[RISCV] Integrate RISCV target in baremetal toolchain object and deprecate

RISCVToolchain object

This patch:
- Adds CXXStdlib, runtimelib and unwindlib defaults for riscv target to
  BareMetal toolchain object.
- Add riscv 32 and 64-bit emulation flags to linker job of BareMetal
  toolchain.
- Removes call to RISCVToolChain object from llvm.

This PR is last patch in the series of patches of merging RISCVToolchain
object into BareMetal toolchain object.

RFC:
https://discourse.llvm.org/t/merging-riscvtoolchain-and-baremetal-toolchains/75524

Change-Id: I2877ac328f55a7638cc185d6034866cbd2ac4203

Author: Garvit Gupta

clang/lib/Driver/CMakeLists.txt

@@ -74,7 +74,6 @@ add_clang_library(clangDriver
   ToolChains/OHOS.cpp
   ToolChains/OpenBSD.cpp
   ToolChains/PS4CPU.cpp
-  ToolChains/RISCVToolchain.cpp
   ToolChains/Solaris.cpp
   ToolChains/SPIRV.cpp
   ToolChains/SPIRVOpenMP.cpp

clang/lib/Driver/Driver.cpp

@@ -41,7 +41,6 @@
 #include "ToolChains/PPCFreeBSD.h"
 #include "ToolChains/PPCLinux.h"
 #include "ToolChains/PS4CPU.h"
-#include "ToolChains/RISCVToolchain.h"
 #include "ToolChains/SPIRV.h"
 #include "ToolChains/SPIRVOpenMP.h"
 #include "ToolChains/SYCL.h"
@@ -6886,16 +6885,11 @@ const ToolChain &Driver::getToolChain(const ArgList &Args,
         TC = std::make_unique<toolchains::AVRToolChain>(*this, Target, Args);
         break;
       case llvm::Triple::msp430:
-        TC =
-            std::make_unique<toolchains::MSP430ToolChain>(*this, Target, Args);
+        TC = std::make_unique<toolchains::MSP430ToolChain>(*this, Target, Args);
         break;
       case llvm::Triple::riscv32:
       case llvm::Triple::riscv64:
-        if (toolchains::RISCVToolChain::hasGCCToolchain(*this, Args))
-          TC =
-              std::make_unique<toolchains::RISCVToolChain>(*this, Target, Args);
-        else
-          TC = std::make_unique<toolchains::BareMetal>(*this, Target, Args);
+        TC = std::make_unique<toolchains::BareMetal>(*this, Target, Args);
         break;
       case llvm::Triple::ve:
         TC = std::make_unique<toolchains::VEToolChain>(*this, Target, Args);

clang/lib/Driver/ToolChains/BareMetal.cpp

@@ -336,6 +336,26 @@ BareMetal::OrderedMultilibs BareMetal::getOrderedMultilibs() const {
   return llvm::reverse(Default);
 }
 
+ToolChain::CXXStdlibType BareMetal::GetDefaultCXXStdlibType() const {
+  if (getTriple().isRISCV() && GCCInstallation.isValid())
+    return ToolChain::CST_Libstdcxx;
+  return ToolChain::CST_Libcxx;
+}
+
+ToolChain::RuntimeLibType BareMetal::GetDefaultRuntimeLibType() const {
+  if (getTriple().isRISCV() && GCCInstallation.isValid())
+    return ToolChain::RLT_Libgcc;
+  return ToolChain::RLT_CompilerRT;
+}
+
+ToolChain::UnwindLibType
+BareMetal::GetUnwindLibType(const llvm::opt::ArgList &Args) const {
+  if (getTriple().isRISCV())
+    return ToolChain::UNW_None;
+
+  return ToolChain::GetUnwindLibType(Args);
+}
+
 void BareMetal::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
                                           ArgStringList &CC1Args) const {
   if (DriverArgs.hasArg(options::OPT_nostdinc))
@@ -534,8 +554,14 @@ void baremetal::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
   CmdArgs.push_back("-Bstatic");
 
-  if (TC.getTriple().isRISCV() && Args.hasArg(options::OPT_mno_relax))
-    CmdArgs.push_back("--no-relax");
+  if (Triple.isRISCV()) {
+    if (Args.hasArg(options::OPT_mno_relax))
+      CmdArgs.push_back("--no-relax");
+    CmdArgs.push_back("-m");
+    CmdArgs.push_back(Arch == llvm::Triple::riscv64 ? "elf64lriscv"
+                                                    : "elf32lriscv");
+    CmdArgs.push_back("-X");
+  }
 
   if (Triple.isARM() || Triple.isThumb()) {
     bool IsBigEndian = arm::isARMBigEndian(Triple, Args);
@@ -622,9 +648,6 @@ void baremetal::Linker::ConstructJob(Compilation &C, const JobAction &JA,
       NeedCRTs)
     CmdArgs.push_back(Args.MakeArgString(TC.GetFilePath(CRTEnd)));
 
-  if (TC.getTriple().isRISCV())
-    CmdArgs.push_back("-X");
-
   // The R_ARM_TARGET2 relocation must be treated as R_ARM_REL32 on arm*-*-elf
   // and arm*-*-eabi (the default is R_ARM_GOT_PREL, used on arm*-*-linux and
   // arm*-*-*bsd).

clang/lib/Driver/ToolChains/BareMetal.h

@@ -54,12 +54,11 @@ class LLVM_LIBRARY_VISIBILITY BareMetal : public Generic_ELF {
     return UnwindTableLevel::None;
   }
 
-  RuntimeLibType GetDefaultRuntimeLibType() const override {
-    return ToolChain::RLT_CompilerRT;
-  }
-  CXXStdlibType GetDefaultCXXStdlibType() const override {
-    return ToolChain::CST_Libcxx;
-  }
+  CXXStdlibType GetDefaultCXXStdlibType() const override;
+
+  RuntimeLibType GetDefaultRuntimeLibType() const override;
+
+  UnwindLibType GetUnwindLibType(const llvm::opt::ArgList &Args) const override;
 
   void
   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,