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[ARM] Introduce -mtp=auto and make it the default #128901

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Merged
merged 2 commits into from
Mar 3, 2025
Merged

[ARM] Introduce -mtp=auto and make it the default #128901

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[ARM] Introduce -mtp=auto and make it the default
Zhenhang1213 Feb 26, 2025
f900dc7
Merge branch 'main' into fix_mtp
Zhenhang1213 Feb 28, 2025
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4 changes: 4 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -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
-------------------------

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2 changes: 1 addition & 1 deletion clang/include/clang/Driver/Options.td
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Expand Up @@ -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'.">;
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15 changes: 9 additions & 6 deletions clang/lib/Driver/ToolChains/Arch/ARM.cpp
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Expand Up @@ -215,7 +215,8 @@ bool arm::isHardTPSupported(const llvm::Triple &Triple) {
// 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)
Expand All @@ -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 (isHardTPSupported(Triple) ? ReadTPMode::TPIDRURO : ReadTPMode::Soft);
}

void arm::setArchNameInTriple(const Driver &D, const ArgList &Args,
Expand Down Expand Up @@ -574,12 +575,14 @@ 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);
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6 changes: 5 additions & 1 deletion clang/test/Driver/arm-thread-pointer.c
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Expand Up @@ -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"