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[ARM] Introduce -mtp=auto and make it the default #128728

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[ARM] Introduce -mtp=auto and make it the default #128728

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019e943
[ARM] Introduce -mtp=auto and make it the default
Zhenhang1213 Feb 24, 2025
1fa8e71
Merge branch 'main' into main
Zhenhang1213 Feb 26, 2025
4cd6ad8
Merge branch 'llvm:main' into main
Zhenhang1213 Feb 26, 2025
ada289d
Merge branch 'llvm:main' into main
Zhenhang1213 Feb 26, 2025
d77c8bb
[ARM] Introduce -mtp=auto and make it the default
Zhenhang1213 Feb 24, 2025
bd0307b
Merge branch 'main' of https://github.com/Zhenhang1213/llvm-project
Zhenhang1213 Feb 26, 2025
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2 changes: 1 addition & 1 deletion clang/include/clang/Driver/Options.td
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Expand Up @@ -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'.">;
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6 changes: 5 additions & 1 deletion clang/lib/Driver/ToolChains/Arch/ARM.cpp
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Expand Up @@ -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 ||
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 ReadTPMode::Auto;
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Is there a way of rewriting this so that we don't have to return Auto from the function? I think the intention is that the logic of handling the mtp option is centralised here. Ideally we should translate Auto to either Soft or TPIDRURO. That would mean it wouldn't need to be handled in setArchNameInTriple

This may need some reorganisation to avoid duplication. Although it may just be simple enough to live with it.

  if (ThreadPointer == ReadTPMode::Auto)
    return (isHardTPSupported(Triple) ? ReadTPMode::TPIDRURO : ReadTPMode::Soft);

At the end we could replace return ReadTPMode::Auto with

return (isHardTPSupported(Triple) ? ReadTPMode::TPIDRURO : ReadTPMode::Soft);

}

void arm::setArchNameInTriple(const Driver &D, const ArgList &Args,
Expand Down Expand Up @@ -580,6 +581,9 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
Features.push_back("+read-tp-tpidruro");
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We're calling getReadTPMode 4 times now, with the same parameters. and I don't think it can return a different value each time. I think this could be simplified to

arm::ReadTPMode TPMode = getReadTPMode(D, Args, Triple, ForAS);
if (TPMode == ReadTPMode::TPIDRURW)
    Features.push_back("+read-tp-tpidrurw");
else if (TPMode == ReadTPMode::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-tpidruro");

const Arg *ArchArg = Args.getLastArg(options::OPT_march_EQ);
const Arg *CPUArg = Args.getLastArg(options::OPT_mcpu_EQ);
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1 change: 1 addition & 0 deletions clang/lib/Driver/ToolChains/Arch/ARM.h
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Expand Up @@ -41,6 +41,7 @@ enum class ReadTPMode {
TPIDRURW,
TPIDRURO,
TPIDRPRW,
Auto,
};

enum class FloatABI {
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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"
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I don't understand how this test matches the change in getARMTargetFeatures. In that function, you respond to -mtp=auto by setting the feature +read-tp-tpidrprw. But here the test is expecting +read-tp-tpidruro, which isn't the same. Can you explain?

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It‘s my fault, I want to set +read-tp-tpidruro by -mtp=auto


// 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"
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