ARMv8.5 Support Lands In GCC Compiler With Latest Spectre Protection

Landing just in time with the GCC 9 branching being imminent is ARMv8.5-A support in the GNU Compiler Collection's ARM64/AArch64 back-end.

This ARMv8.5-A support is an incremental upgrade over the existing ARMv8 support. The ARMv8.5 additions are similar to what we already saw land for LLVM / Clang.

ARMv8.5 does bring some new features like memory tagging, virtualization enhancements, and other bits for what will in turn appear in ARM SoCs in 2019. Arguably most interesting with ARMv8.5 is their hardware protections to fend off Spectre vulnerabilities.

With today's ARMv8.5 landing there is support for the Speculation Battier Instruction as well as for Execution and Data Prediction Restriction Instructions, exposed via the +sb and +predres options with these features being optional. Support for these security features have already been plumbed into GNU Binutils.

The ARMv8.5 support will be exposed with GCC 9 via the -march=armv8.5-a switch as of this commit.