[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

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

[• pcwang-thead]

clang/lib/Driver/ToolChains/Clang.cpp

2190

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

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

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/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;
void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
                                    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();
+    getRISCFeaturesFromMcpu(D, Triple, Args, A, CPU, Features);
+  }
 
   // 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

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);