[scudo] Overhaul hardware CRC32 feature detection

Summary:
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.

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: kubamracek, aemerson, srhines, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D40322

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@318859 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 6 deletions

diff --git a/lib/scudo/scudo_utils.h b/lib/scudo/scudo_utils.h
index cb7300db9..33798194d 100644
--- a/lib/scudo/scudo_utils.h
+++ b/lib/scudo/scudo_utils.h
@@ -21,7 +21,7 @@
 namespace __scudo {
 
 template <class Dest, class Source>
-inline Dest bit_cast(const Source& source) {
+INLINE Dest bit_cast(const Source& source) {
   static_assert(sizeof(Dest) == sizeof(Source), "Sizes are not equal!");
   Dest dest;
   memcpy(&dest, &source, sizeof(dest));
@@ -30,11 +30,7 @@ inline Dest bit_cast(const Source& source) {
 
 void NORETURN dieWithMessage(const char *Format, ...);
 
-enum CPUFeature {
-  CRC32CPUFeature = 0,
-  MaxCPUFeature,
-};
-bool testCPUFeature(CPUFeature Feature);
+bool hasHardwareCRC32();
 
 INLINE u64 rotl(const u64 X, int K) {
   return (X << K) | (X >> (64 - K));