[RISCV] Support -mcpu/mtune=native

[• pcwang-thead]

Summary

We may need hosted Clang/LLVM to compile and getHostCpuName
can be used for native detection.

Tests are added in riscv-cpus.c just like what AArch64/PPC
have done.

[craig.topper]

clang/lib/Driver/ToolChains/Clang.cpp

2190–2193

Why can't we use A->getValue() == "native" here?

[• pcwang-thead]

clang/lib/Driver/ToolChains/Clang.cpp

2190–2193

Because newly-changed support of other targets (like PowerPC) are in this form, so I think this may benefit from simplification?

[kito-cheng]

Maybe we could add test like aarch64?

https://github.com/llvm/llvm-project/blob/main/clang/test/Driver/aarch64-mcpu.c#L20

[kito-cheng]

clang/lib/Driver/ToolChains/Clang.cpp

2190–2193

A->getValue return const char * rather than StringRef? maybe we could use StringRef(A->getValue()) == "native" like X86 to improve that?

https://llvm.org/doxygen/classllvm_1_1opt_1_1Arg.html

grep result from clang folder:

$ grpe "\"native\"" * -R
lib/Driver/ToolChains/Clang.cpp:    if (strcmp(A->getValue(), "native") == 0)
lib/Driver/ToolChains/Clang.cpp:    if (strcmp(A->getValue(), "native") == 0)
lib/Driver/ToolChains/Clang.cpp:    if (Name == "native")
lib/Driver/ToolChains/Clang.cpp:    if (strcmp(A->getValue(), "native") == 0)
lib/Driver/ToolChains/Clang.cpp:    if (Name == "native") {
lib/Driver/ToolChains/CommonArgs.cpp:    // Handle "native" by examining the host. "native" isn't meaningful when
lib/Driver/ToolChains/CommonArgs.cpp:    if (CPU == "native")
lib/Driver/ToolChains/Arch/SystemZ.cpp:    if (CPUName == "native") {
lib/Driver/ToolChains/Arch/X86.cpp:    if (CPU != "native")
lib/Driver/ToolChains/Arch/X86.cpp:    if (StringRef(A->getValue()) == "native") {
lib/Driver/ToolChains/Arch/PPC.cpp:    if (CPUName == "native") {
lib/Driver/ToolChains/Arch/AArch64.cpp:  if (CPU == "native")
lib/Driver/ToolChains/Arch/AArch64.cpp:  if (CPU == "native")
lib/Driver/ToolChains/Arch/AArch64.cpp:  if (Split.first == "native")
lib/Driver/ToolChains/Arch/AArch64.cpp:  if (MtuneLowerCase == "native")
lib/Driver/ToolChains/Arch/Sparc.cpp:    if (CPUName == "native") {
lib/Driver/ToolChains/Arch/ARM.cpp:  if (CPUName == "native") {
lib/Driver/ToolChains/Arch/ARM.cpp:  if (MArch == "native") {
lib/Driver/ToolChains/Arch/ARM.cpp:    if (MCPU == "native")
lib/Driver/ToolChains/Arch/M68k.cpp:    if (CPUName == "native") {

[craig.topper]

clang/lib/Driver/ToolChains/Clang.cpp

2190–2193

Thanks. I guess strcmp makes sense then to avoid an implicit call to strlen in the StringRef constructor.

[• pcwang-thead]

• Add release note.
• Add tests to riscv-cpus.c.
• Add getRISCVTargetCPU.
• Make diagnostic more exact for native.

[kito-cheng]

LGTM

[• pcwang-thead]

Thanks!

clang/docs/ReleaseNotes.rst

 
 - Clang now supports CUDA SDK up to 11.8
 - Added support for targeting sm_{87,89,90} GPUs.
 
 RISC-V Support in Clang
 -----------------------
 - ``sifive-7-rv32`` and ``sifive-7-rv64`` are no longer supported for ``-mcpu``.
   Use ``sifive-e76``, ``sifive-s76``, or ``sifive-u74`` instead.
+- Native detections via ``-mcpu=native`` and ``-mtune=native`` are supported.
 
 X86 Support in Clang
 --------------------
 - Support ``-mindirect-branch-cs-prefix`` for call and jmp to indirect thunk.
 - Fix 32-bit ``__fastcall`` and ``__vectorcall`` ABI mismatch with MSVC.
 - Add ISA of ``AMX-FP16`` which support ``_tile_dpfp16ps``.
 - Switch ``AVX512-BF16`` intrinsics types from ``short`` to ``__bf16``.
 - Add support for ``PREFETCHI`` instructions.

clang/lib/Driver/ToolChains/Arch/RISCV.h

 namespace riscv {
 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);
 StringRef getRISCVArch(const llvm::opt::ArgList &Args,
                        const llvm::Triple &Triple);
+std::string getRISCVTargetCPU(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

clang/lib/Driver/ToolChains/Arch/RISCV.cpp

 #include "ToolChains/CommonArgs.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Options.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/Error.h"
+#include "llvm/Support/Host.h"
 #include "llvm/Support/RISCVISAInfo.h"
 #include "llvm/Support/TargetParser.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace clang::driver;
 using namespace clang::driver::tools;
 using namespace clang;
 using namespace llvm::opt;
static bool getArchFeatures(const Driver &D, StringRef Arch,
   }
 
   (*ISAInfo)->toFeatures(
       Features, [&Args](const Twine &Str) { return Args.MakeArgString(Str); });
   return true;
 }
 
 // Get features except standard extension feature
-static void getRISCFeaturesFromMcpu(const Driver &D, const llvm::Triple &Triple,
-                                    const llvm::opt::ArgList &Args,
-                                    const llvm::opt::Arg *A, StringRef Mcpu,
+static bool getRISCFeaturesFromMcpu(const llvm::Triple &Triple, StringRef Mcpu,
                                     std::vector<StringRef> &Features) {
   bool Is64Bit = Triple.isRISCV64();
   llvm::RISCV::CPUKind CPUKind = llvm::RISCV::parseCPUKind(Mcpu);
-  if (!llvm::RISCV::checkCPUKind(CPUKind, Is64Bit) ||
-      !llvm::RISCV::getCPUFeaturesExceptStdExt(CPUKind, Features)) {
-    D.Diag(clang::diag::err_drv_clang_unsupported) << A->getAsString(Args);
-  }
+  return llvm::RISCV::checkCPUKind(CPUKind, Is64Bit) &&
+         llvm::RISCV::getCPUFeaturesExceptStdExt(CPUKind, Features);
 }
 
 void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
                                    const ArgList &Args,
                                    std::vector<StringRef> &Features) {
   StringRef MArch = getRISCVArch(Args, Triple);
 
   if (!getArchFeatures(D, MArch, Features, Args))
     return;
 
   // If users give march and mcpu, get std extension feature from MArch
   // and other features (ex. mirco architecture feature) from mcpu
-  if (Arg *A = Args.getLastArg(options::OPT_mcpu_EQ))
-    getRISCFeaturesFromMcpu(D, Triple, Args, A, A->getValue(), Features);
+  if (Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
+    StringRef CPU = A->getValue();
+    if (CPU == "native")
+      CPU = llvm::sys::getHostCPUName();
+    if (!getRISCFeaturesFromMcpu(Triple, CPU, Features))
+      D.Diag(clang::diag::err_drv_unsupported_option_argument)
+          << A->getOption().getName() << CPU;
+  }
 
   // Handle features corresponding to "-ffixed-X" options
   if (Args.hasArg(options::OPT_ffixed_x1))
     Features.push_back("+reserve-x1");
   if (Args.hasArg(options::OPT_ffixed_x2))
     Features.push_back("+reserve-x2");
   if (Args.hasArg(options::OPT_ffixed_x3))
     Features.push_back("+reserve-x3");
StringRef riscv::getRISCVArch(const llvm::opt::ArgList &Args,
   // instead of `rv{XLEN}gc` though they are (currently) equivalent.
 
   // 1. If `-march=` is specified, use it.
   if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
     return A->getValue();
 
   // 2. Get march (isa string) based on `-mcpu=`
   if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
-    StringRef MArch = llvm::RISCV::getMArchFromMcpu(A->getValue());
+    StringRef CPU = A->getValue();
+    if (CPU == "native")
+      CPU = llvm::sys::getHostCPUName();
+    StringRef MArch = llvm::RISCV::getMArchFromMcpu(CPU);
     // Bypass if target cpu's default march is empty.
     if (MArch != "")
       return MArch;
   }
 
   // 3. Choose a default based on `-mabi=`
   //
   // ilp32e -> rv32e
else
       return "rv32imafdc";
   } else {
     if (Triple.getOS() == llvm::Triple::UnknownOS)
       return "rv64imac";
     else
       return "rv64imafdc";
   }
 }
+
+std::string riscv::getRISCVTargetCPU(const llvm::opt::ArgList &Args,
+                                     const llvm::Triple &Triple) {
+  std::string CPU;
+  // If we have -mcpu, use that.
+  if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ))
+    CPU = A->getValue();
+
+  // Handle CPU name is 'native'.
+  if (CPU == "native")
+    CPU = llvm::sys::getHostCPUName();
+
+  if (!CPU.empty())
+    return CPU;
+
+  return Triple.isRISCV64() ? "generic-rv64" : "generic-rv32";
+}

clang/lib/Driver/ToolChains/Clang.cpp

void Clang::AddRISCVTargetArgs(const ArgList &Args,
   SetRISCVSmallDataLimit(getToolChain(), Args, CmdArgs);
 
   if (!Args.hasFlag(options::OPT_mimplicit_float,
                     options::OPT_mno_implicit_float, true))
     CmdArgs.push_back("-no-implicit-float");
 
   if (const Arg *A = Args.getLastArg(options::OPT_mtune_EQ)) {
     CmdArgs.push_back("-tune-cpu");
+    if (strcmp(A->getValue(), "native") == 0)
+      CmdArgs.push_back(Args.MakeArgString(llvm::sys::getHostCPUName()));
+    else
       CmdArgs.push_back(A->getValue());
   }
 }
 
 void Clang::AddSparcTargetArgs(const ArgList &Args,
                                ArgStringList &CmdArgs) const {
   sparc::FloatABI FloatABI =
       sparc::getSparcFloatABI(getToolChain().getDriver(), Args);
 

clang/lib/Driver/ToolChains/CommonArgs.cpp

 //===--- CommonArgs.cpp - Args handling for multiple toolchains -*- 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 "CommonArgs.h"
 #include "Arch/AArch64.h"
 #include "Arch/ARM.h"
 #include "Arch/M68k.h"
 #include "Arch/Mips.h"
 #include "Arch/PPC.h"
+#include "Arch/RISCV.h"
 #include "Arch/Sparc.h"
 #include "Arch/SystemZ.h"
 #include "Arch/VE.h"
 #include "Arch/X86.h"
 #include "HIPAMD.h"
 #include "Hexagon.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/LangOptions.h"
case llvm::Triple::csky:
     if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ))
       return A->getValue();
     else if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
       return A->getValue();
     else
       return "ck810";
   case llvm::Triple::riscv32:
   case llvm::Triple::riscv64:
-    if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ))
-      return A->getValue();
-    return "";
+    return riscv::getRISCVTargetCPU(Args, T);
 
   case llvm::Triple::bpfel:
   case llvm::Triple::bpfeb:
     if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ))
       return A->getValue();
     return "";
 
   case llvm::Triple::sparc:

clang/test/Driver/riscv-cpus.c

 // Check target CPUs are correctly passed.
 
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mcpu=rocket-rv32 | FileCheck -check-prefix=MCPU-ROCKET32 %s
 // MCPU-ROCKET32: "-nostdsysteminc" "-target-cpu" "rocket-rv32"
 
 // RUN: %clang --target=riscv64 -### -c %s 2>&1 -mcpu=rocket-rv64 | FileCheck -check-prefix=MCPU-ROCKET64 %s
 // MCPU-ROCKET64: "-nostdsysteminc" "-target-cpu" "rocket-rv64"
 // MCPU-ROCKET64: "-target-feature" "+64bit"
 
+// We cannot check much for -mcpu=native, but it should be replaced by a valid CPU string.
+// RUN: %clang --target=riscv64 -### -c %s 2>&1 -mcpu=native | FileCheck -check-prefix=MCPU-NATIVE %s
+// MCPU-NATIVE-NOT: "-target-cpu" "native"
+
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mtune=rocket-rv32 | FileCheck -check-prefix=MTUNE-ROCKET32 %s
 // MTUNE-ROCKET32: "-tune-cpu" "rocket-rv32"
 
 // RUN: %clang --target=riscv64 -### -c %s 2>&1 -mtune=rocket-rv64 | FileCheck -check-prefix=MTUNE-ROCKET64 %s
 // MTUNE-ROCKET64: "-tune-cpu" "rocket-rv64"
 
 // Check mtune alias CPU has resolved to the right CPU according XLEN.
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mtune=generic | FileCheck -check-prefix=MTUNE-GENERIC-32 %s
 // MTUNE-GENERIC-32: "-tune-cpu" "generic"
 
 // RUN: %clang --target=riscv64 -### -c %s 2>&1 -mtune=generic | FileCheck -check-prefix=MTUNE-GENERIC-64 %s
 // MTUNE-GENERIC-64: "-tune-cpu" "generic"
 
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mtune=rocket | FileCheck -check-prefix=MTUNE-ROCKET-32 %s
 // MTUNE-ROCKET-32: "-tune-cpu" "rocket"
 
 // RUN: %clang --target=riscv64 -### -c %s 2>&1 -mtune=rocket | FileCheck -check-prefix=MTUNE-ROCKET-64 %s
 // MTUNE-ROCKET-64: "-tune-cpu" "rocket"
 
+// We cannot check much for -mtune=native, but it should be replaced by a valid CPU string.
+// RUN: %clang --target=riscv64 -### -c %s 2>&1 -mtune=native | FileCheck -check-prefix=MTUNE-NATIVE %s
+// MTUNE-NATIVE-NOT: "-tune-cpu" "native"
+
 // mcpu with default march
 // RUN: %clang --target=riscv64 -### -c %s 2>&1 -mcpu=sifive-e20 | FileCheck -check-prefix=MCPU-SIFIVE-E20 %s
 // MCPU-SIFIVE-E20: "-nostdsysteminc" "-target-cpu" "sifive-e20"
 // MCPU-SIFIVE-E20: "-target-feature" "+m" "-target-feature" "+c"
 // MCPU-SIFIVE-E20: "-target-abi" "ilp32"
 
 // mcpu with default march
 // RUN: %clang --target=riscv64 -### -c %s 2>&1 -mcpu=sifive-e21 | FileCheck -check-prefix=MCPU-SIFIVE-E21 %s

 // MTUNE-E31-MCPU-E76-SAME: "-target-feature" "+m"
 // MTUNE-E31-MCPU-E76-SAME: "-target-feature" "+a"
 // MTUNE-E31-MCPU-E76-SAME: "-target-feature" "+c"
 // MTUNE-E31-MCPU-E76-SAME: "-tune-cpu" "sifive-e76"
 
 // Check failed cases
 
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mcpu=generic-rv321 | FileCheck -check-prefix=FAIL-MCPU-NAME %s
-// FAIL-MCPU-NAME: error: the clang compiler does not support '-mcpu=generic-rv321'
+// FAIL-MCPU-NAME: error: unsupported argument 'generic-rv321' to option '-mcpu='
 
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mcpu=generic-rv32 -march=rv64i | FileCheck -check-prefix=MISMATCH-ARCH %s
-// MISMATCH-ARCH: error: the clang compiler does not support '-mcpu=generic-rv32'
+// MISMATCH-ARCH: error: unsupported argument 'generic-rv32' to option '-mcpu='
 
 // RUN: %clang --target=riscv32 -### -c %s 2>&1 -mcpu=generic-rv64 | FileCheck -check-prefix=MISMATCH-MCPU %s
-// MISMATCH-MCPU: error: the clang compiler does not support '-mcpu=generic-rv64'
+// MISMATCH-MCPU: error: unsupported argument 'generic-rv64' to option '-mcpu='