Golang patch accepted: runtime detection of ISA level and CPU capabilities

Golang patch accepted: runtime detection of ISA level and CPU capabilities

Commit 40aaf28 adds the functionality of querying about a CPU capability (·cpu+facilities_hasFEATURE(SB)) or ISA level (·cpu+facilities_isPOWERx(SB)) at runtime for ppc64x. These variables are set during runtime from the HWCAP/HWCAP2 bits. This new feature will allow new runtime optimizations that exploit instructions from newer processors without breaking execution for older processors or duplicating code.

This closes issue #16643 and updates #15403.

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