AArch64: add experimental support for address tagging.

Description

AArch64: add experimental support for address tagging.

AArch64 has the ability to use the top 8-bits of an "address" for extra
information, with the memory subsystem automatically masking them off for loads
and stores. When that's happening, we can sometimes skip masks on memory
operations in the compiler.

However, this requires the host OS and support stack to preserve those bits so
it can't be enabled everywhere. In principle iOS 8.0 and above do take the
required precautions and but we'll put it under a flag for now.

Details

Committed
tnorthoverNov 9 2015, 4:44 PM
Parents
rL252572: [CMake] Temporary workaround to support building builtins on darwin with a…
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