[PATCH] D40322: [scudo] Overhaul hardware CRC32 feature detection

[Kostya Kortchinsky via Phabricator via llvm-commits]

cryptoad created this revision.
Herald added subscribers: kristof.beyls, srhines, aemerson.

This patch aims at condensing the hardware CRC32 feature detection and making
it slightly more effective on Android.

The following changes are included:

- remove the `CPUFeature` enum, and get rid of one level of nesting of functions: we only used CRC32, so we just implement and use `hasHardwareCRC32`;
- allow for a weak `getauxval`: the Android toolchain is compiled at API level 14 for Android ARM, meaning no `getauxval` at compile time, yet we will run on API level 27+ devices. The `/proc/self/auxv` fallback can work but is worthless for a process like `init` where the proc filesystem doesn't exist yet. If a weak `getauxval` doesn't exist, then fallback.
- couple of extra corrections.


https://reviews.llvm.org/D40322

Files:
  lib/scudo/scudo_allocator.cpp
  lib/scudo/scudo_utils.cpp
  lib/scudo/scudo_utils.h

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