[ARM] Using cp15 while mtp =auto and arch is arm_arch6k and support thumb2

We follow GCC mtp=auto when arch is arm_arch6k and support thumb2

Author: Zhenhang1213

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

@@ -208,10 +208,17 @@ bool arm::useAAPCSForMachO(const llvm::Triple &T) {
 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);
+  return Triple.isARM() || (Ver >= 7 && AK != llvm::ARM::ArchKind::ARMV8MBaseline);
 }
 
+
+// We follow GCC mtp=auto when arch is arm_arch6k and support thumb2
+bool arm::isHardTPAndThumb2(const llvm::Triple &Triple) {
+  llvm::ARM::ArchKind AK = llvm::ARM::parseArch(Triple.getArchName());
+  return Triple.isARM() && AK >= llvm::ARM::ArchKind::ARMV6K && 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, bool ForAS) {
@@ -240,7 +247,7 @@ arm::ReadTPMode arm::getReadTPMode(const Driver &D, const ArgList &Args,
       D.Diag(diag::err_drv_invalid_mtp) << A->getAsString(Args);
     return ReadTPMode::Invalid;
   }
-  return (isHardTPSupported(Triple) ? ReadTPMode::TPIDRURO : ReadTPMode::Soft);
+  return (isHardTPAndThumb2(Triple) ? ReadTPMode::TPIDRURO : ReadTPMode::Soft);
 }
 
 void arm::setArchNameInTriple(const Driver &D, const ArgList &Args,

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

@@ -57,6 +57,7 @@ FloatABI getARMFloatABI(const Driver &D, const llvm::Triple &Triple,
 void setFloatABIInTriple(const Driver &D, const llvm::opt::ArgList &Args,
                          llvm::Triple &triple);
 bool isHardTPSupported(const llvm::Triple &Triple);
+bool isHardTPAndThumb2(const llvm::Triple &Triple);
 ReadTPMode getReadTPMode(const Driver &D, const llvm::opt::ArgList &Args,
                          const llvm::Triple &Triple, bool ForAS);
 void setArchNameInTriple(const Driver &D, const llvm::opt::ArgList &Args,

clang/test/Driver/arm-thread-pointer.c

@@ -47,3 +47,19 @@
 // RUN: %clang --target=armv7-linux -mtp=auto -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=ARMv7_THREAD_POINTER_Auto %s
 // ARMv7_THREAD_POINTER_Auto: "-target-feature" "+read-tp-tpidruro"
+
+// RUN: %clang --target=armv5t-linux -mtp=auto -### -S %s 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv5t_THREAD_POINTER_Auto %s
+// ARMv5t_THREAD_POINTER_Auto-NOT: "-target-feature" "+read-tp-tpidruro"
+
+// RUN: %clang --target=armv6k-linux -mtp=auto -### -S %s 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv6k_THREAD_POINTER_Auto %s
+// ARMv6k_THREAD_POINTER_Auto: "-target-feature" "+read-tp-tpidruro"
+
+// RUN: %clang --target=armv6-linux -mtp=auto -### -S %s 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv6_THREAD_POINTER_Auto %s
+// ARMv6_THREAD_POINTER_Auto-NOT: "-target-feature" "+read-tp-tpidruro"
+
+// RUN: %clang --target=armv6kz-linux -mtp=auto -### -S %s 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv6kz_THREAD_POINTER_Auto %s
+// ARMv6kz_THREAD_POINTER_Auto: "-target-feature" "+read-tp-tpidruro"