[clang][ARM] only check -mtp=cp15 for non-asm sources

[nickdesaulniers]

Summary

This diagnostic is really to highlight lack of support for hard thread
pointers in post-RA instruction scheduling for non-armv6k+ targets;
something that isn't run for assembler sources.

Fixes: https://github.com/ClangBuiltLinux/linux/issues/1502
Link: https://lore.kernel.org/all/[e-mail]/

[nickdesaulniers]

• rebase

[nickdesaulniers]

• update description

[nickdesaulniers]

• try to fix rebase

[peter.smith]

LGTM too.

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

 FloatABI getDefaultFloatABI(const llvm::Triple &Triple);
 FloatABI getARMFloatABI(const ToolChain &TC, const llvm::opt::ArgList &Args);
 FloatABI getARMFloatABI(const Driver &D, const llvm::Triple &Triple,
                         const llvm::opt::ArgList &Args);
 void setFloatABIInTriple(const Driver &D, const llvm::opt::ArgList &Args,
                          llvm::Triple &triple);
 bool isHardTPSupported(const llvm::Triple &Triple);
 ReadTPMode getReadTPMode(const Driver &D, const llvm::opt::ArgList &Args,
-                         const llvm::Triple &Triple);
+                         const llvm::Triple &Triple, bool ForAS);
 void setArchNameInTriple(const Driver &D, const llvm::opt::ArgList &Args,
                          types::ID InputType, llvm::Triple &Triple);
 
 bool useAAPCSForMachO(const llvm::Triple &T);
 void getARMArchCPUFromArgs(const llvm::opt::ArgList &Args,
                            llvm::StringRef &Arch, llvm::StringRef &CPU,
                            bool FromAs = false);
 void getARMTargetFeatures(const Driver &D, const llvm::Triple &Triple,

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

bool arm::isHardTPSupported(const llvm::Triple &Triple) {
   int Ver = getARMSubArchVersionNumber(Triple);
   llvm::ARM::ArchKind AK = llvm::ARM::parseArch(Triple.getArchName());
   return Triple.isARM() || AK == llvm::ARM::ArchKind::ARMV6T2 ||
          (Ver >= 7 && AK != llvm::ARM::ArchKind::ARMV8MBaseline);
 }
 
 // Select mode for reading thread pointer (-mtp=soft/cp15).
 arm::ReadTPMode arm::getReadTPMode(const Driver &D, const ArgList &Args,
-                                   const llvm::Triple &Triple) {
+                                   const llvm::Triple &Triple, bool ForAS) {
   if (Arg *A = Args.getLastArg(options::OPT_mtp_mode_EQ)) {
     arm::ReadTPMode ThreadPointer =
         llvm::StringSwitch<arm::ReadTPMode>(A->getValue())
             .Case("cp15", ReadTPMode::Cp15)
             .Case("soft", ReadTPMode::Soft)
             .Default(ReadTPMode::Invalid);
-    if (ThreadPointer == ReadTPMode::Cp15 && !isHardTPSupported(Triple)) {
+    if (ThreadPointer == ReadTPMode::Cp15 && !isHardTPSupported(Triple) &&
+        !ForAS) {
       D.Diag(diag::err_target_unsupported_tp_hard) << Triple.getArchName();
       return ReadTPMode::Invalid;
     }
     if (ThreadPointer != ReadTPMode::Invalid)
       return ThreadPointer;
     if (StringRef(A->getValue()).empty())
       D.Diag(diag::err_drv_missing_arg_mtp) << A->getAsString(Args);
     else
for (const Arg *A :
           WaHDiv = std::make_pair(A, Value.substr(8));
         } else if (Value.startswith("-march=")) {
           WaArch = std::make_pair(A, Value.substr(7));
         }
       }
     }
   }
 
-  if (getReadTPMode(D, Args, Triple) == ReadTPMode::Cp15)
+  if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::Cp15)
     Features.push_back("+read-tp-hard");
 
   const Arg *ArchArg = Args.getLastArg(options::OPT_march_EQ);
   const Arg *CPUArg = Args.getLastArg(options::OPT_mcpu_EQ);
   StringRef ArchName;
   StringRef CPUName;
   unsigned ArchArgFPUID = llvm::ARM::FK_INVALID;
   unsigned CPUArgFPUID = llvm::ARM::FK_INVALID;

clang/test/Driver/clang-translation.c

 // RUN: %clang -target armv6k-linux -mtp=cp15 -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=ARM_THREAD_POINTER-HARD %s
 // RUN: %clang -target armv6-linux -mtp=cp15 -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=ARM_THREAD_POINTER-HARD %s
 // RUN: %clang -target armv5t-linux -mtp=cp15 -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=ARM_THREAD_POINTER-HARD %s
 // ARM_THREAD_POINTER-HARD: "-target-feature" "+read-tp-hard"
 
+// RUN: %clang -target armv5t-linux -mtp=cp15 -x assembler -### %s 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv5_THREAD_POINTER_ASSEMBLER %s
+// ARMv5_THREAD_POINTER_ASSEMBLER-NOT: hardware TLS register is not supported for the armv5 sub-architecture
+
 // RUN: %clang -target armv6-linux -mthumb -mtp=cp15 -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=THUMBv6_THREAD_POINTER_UNSUPP %s
 // RUN: %clang -target thumbv6-linux -mthumb -mtp=cp15 -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=THUMBv6_THREAD_POINTER_UNSUPP %s
 // THUMBv6_THREAD_POINTER_UNSUPP: hardware TLS register is not supported for the thumbv6 sub-architecture
 
 // RUN: %clang -target armv7-linux -mtp=soft -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=ARMv7_THREAD_POINTER_SOFT %s