[FMV][compiler-rt] Fix cpu features initialization. #95149
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To detect features we either use HWCAPs or directly extract system register bitfields and compare with a value. In many cases equality comparisons give wrong results for example FEAT_SVE is not set if SVE2 is available (see the issue llvm#93651). I am also making the access to __aarch64_cpu_features atomic. The corresponding PR for the ACLE specification is ARM-software/acle#322.
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| if (__atomic_load_n(&__aarch64_cpu_features.features, __ATOMIC_RELAXED)) | ||
| return; | ||
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| __init_cpu_features(); | ||
| } | ||
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| __attribute__((target("sve"))) long | ||
| __arm_get_current_vg(void) __arm_streaming_compatible { |
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can this ever get called before __init_cpu_features()?
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To detect features we either use HWCAPs or directly extract system register bitfields and compare with a value. In many cases equality comparisons give wrong results for example FEAT_SVE is not set if SVE2 is available (see the issue llvm#93651). I am also making the access to __aarch64_cpu_features atomic. The corresponding PR for the ACLE specification is ARM-software/acle#322.
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To detect features we either use HWCAPs or directly extract system register bitfields and compare with a value. In many cases equality comparisons give wrong results for example FEAT_SVE is not set if SVE2 is available (see the issue #93651). I am also making the access to __aarch64_cpu_features atomic.
The corresponding PR for the ACLE specification is ARM-software/acle#322.