[AArch64] Support selecting TPIDR_EL[1-3] as the thread base

[philip.derrin]

Summary

Add an -mtp=el[0-3] option to select which of the AArch64 thread ID registers will be used for the TLS base pointer.

This is a followup to D54685 which added subtarget features to enable accesses to the privileged thread ID registers.

[olista01]

Is there an existing compiler which this option is trying to be compatible with? GCC for AArch64 doesn't currently have an option for this, so we don't have to worry about compatibility with that. If possible, I'd prefer for the option to be "-mtp=", to match the option accepted by clang and GCC for AArch32.

[philip.derrin]

In D59631#1437744, @olista01 wrote:

Is there an existing compiler which this option is trying to be compatible with? GCC for AArch64 doesn't currently have an option for this, so we don't have to worry about compatibility with that. If possible, I'd prefer for the option to be "-mtp=", to match the option accepted by clang and GCC for AArch32.

No, there's no existing option as far as I'm aware.

I'm happy to use -mtp=, as long as it is ok for it to remain in Group<m_arm_Features_Group> and to list values for both AArch32 and AArch64. It looks like these things only affect value completion and documentation; is that correct?

[philip.derrin]

Merged -mtpidr= with existing AArch32 option -mtp=

[olista01]

I can't see any other uses of the option groups, or any way to put an option into two groups, so this LGTM.

I'll commit it for you as before.

clang/include/clang/Basic/DiagnosticDriverKinds.td

   "invalid thread pointer reading mode '%0'">;
 def err_drv_missing_arg_mtp : Error<
   "missing argument to '%0'">;
+def err_drv_invalid_mtpidr : Error<
+  "invalid thread pointer exception level '%0'">;
 def err_drv_invalid_libcxx_deployment : Error<
   "invalid deployment target for -stdlib=libc++ (requires %0 or later)">;
 def err_drv_invalid_argument_to_fdebug_prefix_map : Error<

clang/include/clang/Driver/Options.td

 foreach i = {1-7,9-15,18,20-28} in
   def ffixed_x#i : Flag<["-"], "ffixed-x"#i>, Group<m_aarch64_Features_Group>,
     HelpText<"Reserve the "#i#" register (AArch64 only)">;
+def mtpidr_EQ : Joined<["-"], "mtpidr=">, Group<m_aarch64_Features_Group>, Values<"el0,el1,el2,el3">,
+  HelpText<"Read thread pointer for specified exception level (AArch64 only)">;
 
 foreach i = {8-15,18} in
   def fcall_saved_x#i : Flag<["-"], "fcall-saved-x"#i>, Group<m_aarch64_Features_Group>,

clang/lib/Driver/ToolChains/Arch/AArch64.cpp

     Features.push_back("-neon");
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_mtpidr_EQ)) {
+    StringRef Mtpidr = A->getValue();
+    if (Mtpidr == "el3")
+      Features.push_back("+tpidr-el3");
+    else if (Mtpidr == "el2")
+      Features.push_back("+tpidr-el2");
+    else if (Mtpidr == "el1")
+      Features.push_back("+tpidr-el1");
+    else if (Mtpidr != "el0")
+      D.Diag(diag::err_drv_invalid_mtpidr) << A->getAsString(Args);
+  }
+
   // En/disable crc
   if (Arg *A = Args.getLastArg(options::OPT_mcrc, options::OPT_mnocrc)) {
     if (A->getOption().matches(options::OPT_mcrc))

clang/test/Driver/clang-translation.c

 // RUN: FileCheck -check-prefix=ARMv7_THREAD_POINTER_NON %s
 // ARMv7_THREAD_POINTER_NON-NOT: "-target-feature" "+read-tp-hard"
 
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_NON %s
+// ARMv8_THREAD_POINTER_NON-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_NON-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_NON-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtpidr=el0 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL0 %s
+// ARMv8_THREAD_POINTER_EL0-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL0-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL0-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtpidr=el1 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL1 %s
+// ARMv8_THREAD_POINTER_EL1: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL1-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL1-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtpidr=el2 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL2 %s
+// ARMv8_THREAD_POINTER_EL2-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL2: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL2-NOT: "-target-feature" "+tpidr-el3"
+
+// RUN: %clang -target aarch64-linux -### -S %s -arch armv8a -mtpidr=el3 2>&1 | \
+// RUN: FileCheck -check-prefix=ARMv8_THREAD_POINTER_EL3 %s
+// ARMv8_THREAD_POINTER_EL3-NOT: "-target-feature" "+tpidr-el1"
+// ARMv8_THREAD_POINTER_EL3-NOT: "-target-feature" "+tpidr-el2"
+// ARMv8_THREAD_POINTER_EL3: "-target-feature" "+tpidr-el3"
+
 // RUN: %clang -target powerpc64-unknown-linux-gnu \
 // RUN: -### -S %s -mcpu=G5 2>&1 | FileCheck -check-prefix=PPCG5 %s
 // PPCG5: clang