[clang] [ARM] Aligned mtp behavior and gcc (PR #128728)

[via cfe-commits]

https://github.com/Zhenhang1213 updated https://github.com/llvm/llvm-project/pull/128728

>From 4ca0fa7f65901638ea5bae9ad00a76e1bb5f37c9 Mon Sep 17 00:00:00 2001
From: Austin <superw1213 at 163.com>
Date: Tue, 25 Feb 2025 01:24:24 +0800
Subject: [PATCH] [ARM] Aligned mtp behavior and gcc

Fix #123864, resolved of the different form behavior of mtp
---
 clang/include/clang/Driver/Options.td    | 2 +-
 clang/lib/Driver/ToolChains/Arch/ARM.cpp | 6 +++++-
 clang/lib/Driver/ToolChains/Arch/ARM.h   | 1 +
 clang/test/Driver/arm-thread-pointer.c   | 6 +++++-
 4 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index e521cbf678d93..2bd6076bea5d4 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4711,7 +4711,7 @@ 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'.">;
diff --git a/clang/lib/Driver/ToolChains/Arch/ARM.cpp b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
index 3aee540d501be..3567089f53479 100644
--- a/clang/lib/Driver/ToolChains/Arch/ARM.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
@@ -223,6 +223,7 @@ arm::ReadTPMode arm::getReadTPMode(const Driver &D, const ArgList &Args,
             .Case("tpidruro", ReadTPMode::TPIDRURO)
             .Case("tpidrprw", ReadTPMode::TPIDRPRW)
             .Case("soft", ReadTPMode::Soft)
+            .Case("auto", ReadTPMode::Auto)
             .Default(ReadTPMode::Invalid);
     if ((ThreadPointer == ReadTPMode::TPIDRURW ||
          ThreadPointer == ReadTPMode::TPIDRURO ||
@@ -239,7 +240,7 @@ 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 ReadTPMode::Auto;
 }
 
 void arm::setArchNameInTriple(const Driver &D, const ArgList &Args,
@@ -580,6 +581,9 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
     Features.push_back("+read-tp-tpidruro");
   if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::TPIDRPRW)
     Features.push_back("+read-tp-tpidrprw");
+  if (getReadTPMode(D, Args, Triple, ForAS) == ReadTPMode::Auto
+      && isHardTPSupported(Triple) && !ForAS)
+    Features.push_back("+read-tp-tpidrprw");
 
   const Arg *ArchArg = Args.getLastArg(options::OPT_march_EQ);
   const Arg *CPUArg = Args.getLastArg(options::OPT_mcpu_EQ);
diff --git a/clang/lib/Driver/ToolChains/Arch/ARM.h b/clang/lib/Driver/ToolChains/Arch/ARM.h
index a23a8793a89e2..622383cf0025d 100644
--- a/clang/lib/Driver/ToolChains/Arch/ARM.h
+++ b/clang/lib/Driver/ToolChains/Arch/ARM.h
@@ -41,6 +41,7 @@ enum class ReadTPMode {
   TPIDRURW,
   TPIDRURO,
   TPIDRPRW,
+  Auto,
 };
 
 enum class FloatABI {
diff --git a/clang/test/Driver/arm-thread-pointer.c b/clang/test/Driver/arm-thread-pointer.c
index 5521e1865b276..985c5046f6d26 100644
--- a/clang/test/Driver/arm-thread-pointer.c
+++ b/clang/test/Driver/arm-thread-pointer.c
@@ -42,4 +42,8 @@
 
 // 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"