Fix mtp

clang/docs/ReleaseNotes.rst

@@ -124,6 +124,10 @@ Deprecated Compiler Flags
 Modified Compiler Flags
 -----------------------
 
+- The ARM AArch32 ``-mtp`` option accepts and defaults to ``auto``, a value of ``auto`` uses the best available method of providing the frame pointer supported by the hardware. This matches
+  the behavior of ``-mtp`` in gcc. This changes the default behavior for ARM targets that provide the ``TPIDRURO`` register as this will be used instead of a call to the ``__aeabi_read_tp``.
+  Programs that use ``__aeabi_read_tp`` but do not use the ``TPIDRURO`` register must use ``-mtp=soft``. Fixes #123864
+
 Removed Compiler Flags
 -------------------------
 

clang/include/clang/Driver/Options.td

@@ -4729,7 +4729,7 @@ def mexecute_only : Flag<["-"], "mexecute-only">, Group<m_arm_Features_Group>,
 def mno_execute_only : Flag<["-"], "mno-execute-only">, Group<m_arm_Features_Group>,
   HelpText<"Allow generation of data access to code sections (ARM only)">;
 let Flags = [TargetSpecific] in {
-def mtp_mode_EQ : Joined<["-"], "mtp=">, Group<m_arm_Features_Group>, Values<"soft,cp15,tpidrurw,tpidruro,tpidrprw,el0,el1,el2,el3,tpidr_el0,tpidr_el1,tpidr_el2,tpidr_el3,tpidrro_el0">,
+def mtp_mode_EQ : Joined<["-"], "mtp=">, Group<m_arm_Features_Group>, Values<"soft,cp15,tpidrurw,tpidruro,tpidrprw,el0,el1,el2,el3,tpidr_el0,tpidr_el1,tpidr_el2,tpidr_el3,tpidrro_el0,auto">,
   HelpText<"Thread pointer access method. "
            "For AArch32: 'soft' uses a function call, or 'tpidrurw', 'tpidruro' or 'tpidrprw' use the three CP15 registers. 'cp15' is an alias for 'tpidruro'. "
            "For AArch64: 'tpidr_el0', 'tpidr_el1', 'tpidr_el2', 'tpidr_el3' or 'tpidrro_el0' use the five system registers. 'elN' is an alias for 'tpidr_elN'.">;

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

@@ -208,14 +208,22 @@ 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) {
-  if (Arg *A = Args.getLastArg(options::OPT_mtp_mode_EQ)) {
+  Arg *A = Args.getLastArg(options::OPT_mtp_mode_EQ);
+  if (A && A->getValue() != StringRef("auto")) {
     arm::ReadTPMode ThreadPointer =
         llvm::StringSwitch<arm::ReadTPMode>(A->getValue())
             .Case("cp15", ReadTPMode::TPIDRURO)
@@ -239,7 +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 ReadTPMode::Soft;
+  return (isHardTPAndThumb2(Triple) ? ReadTPMode::TPIDRURO : ReadTPMode::Soft);
 }
 
 void arm::setArchNameInTriple(const Driver &D, const ArgList &Args,
@@ -574,12 +582,14 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
       A->ignoreTargetSpecific();
   }
 
-  if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::TPIDRURW)
+  arm::ReadTPMode TPMode = getReadTPMode(D, Args, Triple, ForAS);
+
+  if (TPMode == ReadTPMode::TPIDRURW)
     Features.push_back("+read-tp-tpidrurw");
-  if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::TPIDRURO)
-    Features.push_back("+read-tp-tpidruro");
-  if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::TPIDRPRW)
+  else if (TPMode == ReadTPMode::TPIDRPRW)
     Features.push_back("+read-tp-tpidrprw");
+  else if (TPMode == ReadTPMode::TPIDRURO)
+    Features.push_back("+read-tp-tpidruro");
 
   const Arg *ArchArg = Args.getLastArg(options::OPT_march_EQ);
   const Arg *CPUArg = Args.getLastArg(options::OPT_mcpu_EQ);

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

@@ -42,4 +42,24 @@
 
 // RUN: %clang --target=armv7-linux -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=ARMv7_THREAD_POINTER_NON %s
-// ARMv7_THREAD_POINTER_NON-NOT: "-target-feature" "+read-tp-tpidruro"
+// ARMv7_THREAD_POINTER_NON: "-target-feature" "+read-tp-tpidruro"
+
+// 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"