tree 60e1562120da96d27780c63d7468fd21c63f7630
parent c3d8c8b9b4664ae62eb54d7ad8120b84f8c70748
author Shac Ron <sron@google.com> 1544585687 -0800
committer CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> 1544744111 +0000

[arm64] Replace some inline asm with arm_acle standard extensions.

Replaced uses of inline assembly with language extensions where available.
The extensions come from the <arm_acle.h>, which is included with gcc
and clang, though the gcc version is woefully incomplete. Local
arm_acle.h implements missing functionality.

__arm_rsr/wsr for reading and writing MSRs.
__dmb/dsb/isb for barriers.

Some minor optimizations of ISB abundance, as they were previously
included by default in ARM64_WRITE_SYSREG(). Conservatively removed some
in cases where it seemed like they could be combined.

The builtins provide the compiler more information about the operation
that's being done, and allow improved optimization, instruction fencing,
as well as safety (avoiding common assembler pitfalls such as incomplete
side effect flags).

Change-Id: I8b776d11095b333f6614d6e9a6c485efd32346e4
Test: Builds with Clang and GCC, manual verification of code gen, qemu boot.