[RISCV] Make -march=rv{32,64}gc the default in RISC-V Linux

[rogfer01]

Summary

This is the logical follow-up of D65634.

[luismarques]

LGTM.

[rogfer01]

Thanks for the review @luismarques

I plan to commit this shortly.

cfe/trunk/lib/Driver/ToolChains/Arch/RISCV.h

 #include "llvm/Option/Option.h"
 #include <string>
 #include <vector>
 
 namespace clang {
 namespace driver {
 namespace tools {
 namespace riscv {
-void getRISCVTargetFeatures(const Driver &D, const llvm::opt::ArgList &Args,
+void getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
+                            const llvm::opt::ArgList &Args,
                             std::vector<llvm::StringRef> &Features);
 StringRef getRISCVABI(const llvm::opt::ArgList &Args,
                       const llvm::Triple &Triple);
 } // end namespace riscv
 } // namespace tools
 } // end namespace driver
 } // end namespace clang
 
 #endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_ARCH_RISCV_H

cfe/trunk/lib/Driver/ToolChains/Arch/RISCV.cpp

 //===--- RISCV.cpp - RISCV Helpers for Tools --------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "RISCV.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Options.h"
 #include "llvm/Option/ArgList.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/Support/TargetParser.h"
 #include "llvm/Support/raw_ostream.h"
 #include "ToolChains/CommonArgs.h"
 
 using namespace clang::driver;
 using namespace clang::driver::tools;
 using namespace clang;
 using namespace llvm::opt;
static bool getArchFeatures(const Driver &D, StringRef MArch,
   // TODO: It is illegal to specify 'e' extensions with 'f' and 'd'.
 
   // Handle all other types of extensions.
   getExtensionFeatures(D, Args, Features, MArch, OtherExts);
 
   return true;
 }
 
-void riscv::getRISCVTargetFeatures(const Driver &D, const ArgList &Args,
+void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
+                                   const ArgList &Args,
                                    std::vector<StringRef> &Features) {
-  if (const Arg *A = Args.getLastArg(options::OPT_march_EQ)) {
-    StringRef MArch = A->getValue();
+  llvm::Optional<StringRef> MArch;
+  if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
+    MArch = A->getValue();
+  else if (Triple.getOS() == llvm::Triple::Linux)
+    // RISC-V Linux defaults to rv{32,64}gc.
+    MArch = Triple.getArch() == llvm::Triple::riscv32 ? "rv32gc" : "rv64gc";
 
-    if (!getArchFeatures(D, MArch, Features, Args))
-      return;
-  }
+  if (MArch.hasValue() && !getArchFeatures(D, *MArch, Features, Args))
 
   // -mrelax is default, unless -mno-relax is specified.
   if (Args.hasFlag(options::OPT_mrelax, options::OPT_mno_relax, true))
     Features.push_back("+relax");
   else
     Features.push_back("-relax");
 
   // GCC Compatibility: -mno-save-restore is default, unless -msave-restore is

cfe/trunk/lib/Driver/ToolChains/Clang.cpp

static void getTargetFeatures(const ToolChain &TC, const llvm::Triple &Triple,
 
   case llvm::Triple::ppc:
   case llvm::Triple::ppc64:
   case llvm::Triple::ppc64le:
     ppc::getPPCTargetFeatures(D, Triple, Args, Features);
     break;
   case llvm::Triple::riscv32:
   case llvm::Triple::riscv64:
-    riscv::getRISCVTargetFeatures(D, Args, Features);
+    riscv::getRISCVTargetFeatures(D, Triple, Args, Features);
     break;
   case llvm::Triple::systemz:
     systemz::getSystemZTargetFeatures(Args, Features);
     break;
   case llvm::Triple::aarch64:
   case llvm::Triple::aarch64_be:
     aarch64::getAArch64TargetFeatures(D, Triple, Args, Features);
     break;

cfe/trunk/test/Driver/riscv-features.c

 // DEFAULT: "-target-feature" "+relax"
 // DEFAULT-NOT: "-target-feature" "-relax"
 
 // RUN: %clang -target riscv32-unknown-elf -### %s -msave-restore 2>&1 | FileCheck %s -check-prefix=SAVE-RESTORE
 // RUN: %clang -target riscv32-unknown-elf -### %s -mno-save-restore 2>&1 | FileCheck %s -check-prefix=NO-SAVE-RESTORE
 
 // SAVE-RESTORE: warning: the clang compiler does not support '-msave-restore'
 // NO-SAVE-RESTORE-NOT: warning: the clang compiler does not support
-// DEFAULT-NOT: warning: the clang compiler does not support
+// DEFAULT-NOT: warning: the clang compiler does not support
+
+// RUN: %clang -target riscv32-linux -### %s -fsyntax-only 2>&1 \
+// RUN:   | FileCheck %s -check-prefix=DEFAULT-LINUX
+// RUN: %clang -target riscv64-linux -### %s -fsyntax-only 2>&1 \
+// RUN:   | FileCheck %s -check-prefix=DEFAULT-LINUX
+
+// DEFAULT-LINUX: "-target-feature" "+m"
+// DEFAULT-LINUX-SAME: "-target-feature" "+a"
+// DEFAULT-LINUX-SAME: "-target-feature" "+f"
+// DEFAULT-LINUX-SAME: "-target-feature" "+d"
+// DEFAULT-LINUX-SAME: "-target-feature" "+c"