[Driver] Reject -march= for ppc

[MaskRay]

Summary

Clang -march= for ppc triples currently leads to an
-Wunused-command-line-argument warning but GCC rejects -march=.

error: unrecognized command-line option ‘-march=xxx’

Let's reject -march= as well similar to the Sparc change D130273.

Close https://github.com/llvm/llvm-project/issues/57587

[nemanjai]

I am perfectly fine with this. That option is quite problematic. LGTM.

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

 
 enum class ReadGOTPtrMode {
   Bss,
   SecurePlt,
 };
 
 FloatABI getPPCFloatABI(const Driver &D, const llvm::opt::ArgList &Args);
 
-std::string getPPCTargetCPU(const llvm::opt::ArgList &Args,
+std::string getPPCTargetCPU(const Driver &D, const llvm::opt::ArgList &Args,
                             const llvm::Triple &T);
 std::string getPPCTuneCPU(const llvm::opt::ArgList &Args,
                           const llvm::Triple &T);
 const char *getPPCAsmModeForCPU(StringRef Name);
 ReadGOTPtrMode getPPCReadGOTPtrMode(const Driver &D, const llvm::Triple &Triple,
                                     const llvm::opt::ArgList &Args);
 
 void getPPCTargetFeatures(const Driver &D, const llvm::Triple &Triple,

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

 /// Get the (LLVM) name of the PowerPC cpu we are tuning for.
 std::string ppc::getPPCTuneCPU(const ArgList &Args, const llvm::Triple &T) {
   if (Arg *A = Args.getLastArg(clang::driver::options::OPT_mtune_EQ))
     return normalizeCPUName(A->getValue(), T);
   return getPPCGenericTargetCPU(T);
 }
 
 /// Get the (LLVM) name of the PowerPC cpu we are targeting.
-std::string ppc::getPPCTargetCPU(const ArgList &Args, const llvm::Triple &T) {
+std::string ppc::getPPCTargetCPU(const Driver &D, const ArgList &Args,
+                                 const llvm::Triple &T) {
+  if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_march_EQ)) {
+    D.Diag(diag::err_drv_unsupported_opt_for_target)
+        << A->getSpelling() << T.getTriple();
+  }
   if (Arg *A = Args.getLastArg(clang::driver::options::OPT_mcpu_EQ))
     return normalizeCPUName(A->getValue(), T);
   return getPPCGenericTargetCPU(T);
 }
 
 const char *ppc::getPPCAsmModeForCPU(StringRef Name) {
   return llvm::StringSwitch<const char *>(Name)
       .Case("pwr7", "-mpower7")

clang/lib/Driver/ToolChains/CommonArgs.cpp

case llvm::Triple::nvptx64:
     if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
       return A->getValue();
     return "";
 
   case llvm::Triple::ppc:
   case llvm::Triple::ppcle:
   case llvm::Triple::ppc64:
   case llvm::Triple::ppc64le:
-    return ppc::getPPCTargetCPU(Args, T);
+    return ppc::getPPCTargetCPU(D, Args, T);
 
   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";

clang/test/Driver/ppc-cpus.c

 // RUN: %clang -### -c --target=powerpc64le %s -mcpu=power9 -mtune=power10 2>&1 | FileCheck %s --check-prefix=TUNE-LONG
 // TUNE-LONG: "-target-cpu" "pwr9" "-tune-cpu" "pwr10"
 
 /// Test mcpu options that are equivalent to "generic"
 // RUN: %clang -### -c -target powerpc64 %s -mcpu=generic 2>&1 | FileCheck %s --check-prefix=GENERIC
 // RUN: %clang -### -c -target powerpc64 %s -mcpu=405     2>&1 | FileCheck %s --check-prefix=GENERIC
 //
 // GENERIC: "-target-cpu" "ppc64"
+
+// RUN: %clang -### -c --target=powerpc64 %s -march=generic 2>&1 | FileCheck --check-prefix=MARCH %s
+// MARCH: error: unsupported option '-march=' for target 'powerpc64'