[AArch64][compiler-rt] Add a function returning the current vector length #92921
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…ngth get_runtime_vl emits a cntd instruction if SVE is available at runtime, otherwise it will return 0.
kmclaughlin-arm
requested review from
aemerson,
rsandifo-arm,
sdesmalen-arm and
efriedma-quic
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✅ With the latest revision this PR passed the C/C++ code formatter. |
| __init_cpu_features(); | ||
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| __attribute__((target("sve"))) long emit_cntd(void) { |
| return vl; | ||
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| long get_runtime_vl(void) { |
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This probably should be prefixed with __aarch64
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Hi @efriedma-quic, I've added this routine to the ABI document in ARM-software/abi-aa#263 and renamed it to __arm_get_current_vg.
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| // See https://llvm.org/LICENSE.txt for license information. | |||
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | |||
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| #include "../cpu_model/aarch64.c" | |||
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cpu_model/aarch64.c isn't a header; including it seem wrong.
ARM-software/abi-aa#263 - Renamed get_runtime_vl to __arm_get_current_vg - Also return VG if currently in streaming-mode - Added static to get_aarch64_cpu_features - Added aarch64.h and included in sme-abi-init.c
…me_state, to check if currently in streaming mode.
| FEAT_INIT // Used as flag of features initialization completion | ||
| }; | ||
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| long long get_features(void); |
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This exports a function named get_features from compiler-rt... probably you want to hide it somehow (__ prefix, or make it static).
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| long long __get_aarch64_features(void); | ||
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| void CONSTRUCTOR_ATTRIBUTE __init_cpu_features(void); |
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You shouldn't need CONSTRUCTOR_ATTRIBUTE on the declaration here, I think.
| extern struct SME_STATE __arm_sme_state(void) __arm_streaming_compatible; | ||
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| __attribute__((target("sve"))) long | ||
| __arm_get_current_vg(void) __arm_streaming_compatible { |
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Maybe split this into a separate file, so code using the other stuff defined in this file doesn't pull in the constructor? I assume __arm_get_current_vg won't be used in most configurations.
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I've split this into a separate file and replaced the use of has_sme() with __aarch64_has_sme_and_tpidr2_el0.
| FEAT_INIT // Used as flag of features initialization completion | ||
| }; | ||
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| long long __get_aarch64_features(void); |
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Looking again... maybe we should just poke at __aarch64_cpu_features directly, instead of adding this function? __aarch64_cpu_features is already part of the ABI (clang codegen knows about it).
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Thanks, I've removed __get_aarch64_features. I'd missed that clang was also using __aarch64_cpu_features.
- Removed __get_aarch64_features. - Split out changes for __arm_get_current_vg into a new file (sme-abi-vg.c) and removed from sme-abi-init.c.
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This change results in The new C file, |
When llvm#92921 added the `__arm_get_current_vg` functionality, it used the FMV feature bits mechanism rather than the existing mechanism that was previously added for SME that called `getauxval` (on Linux platforms) or `__aarch64_sme_accessible` (required for baremetal libraries). It seems simpler to always use the FMV feature bits mechanism, but for baremetal targets we still need to rely on `__arm_sme_accessible`.
When llvm#92921 added the `__arm_get_current_vg` functionality, it used the FMV feature bits mechanism rather than the existing mechanism that was previously added for SME that called `getauxval` (on Linux platforms) or `__aarch64_sme_accessible` (required for baremetal libraries). It seems simpler to always use the FMV feature bits mechanism, but for baremetal targets we still need to rely on `__arm_sme_accessible`.
When llvm#92921 added the `__arm_get_current_vg` functionality, it used the FMV feature bits mechanism rather than the existing mechanism that was previously added for SME that called `getauxval` (on Linux platforms) or `__aarch64_sme_accessible` (required for baremetal libraries). It seems simpler to always use the FMV feature bits mechanism, but for baremetal targets we still need to rely on `__arm_sme_accessible`.
…features. (#119414) When #92921 added the `__arm_get_current_vg` functionality, it used the FMV feature bits mechanism rather than the mechanism that was previously added for SME which called `getauxval` on Linux platforms or `__aarch64_sme_accessible` required for baremetal libraries. It is better to always use `__aarch64_cpu_features`. For baremetal we still need to rely on `__arm_sme_accessible` to initialise the struct.
get_runtime_vl emits a cntd instruction if SVE is available at runtime,
otherwise it will return 0.