mfbhrbe

Move From Branch History Rolling Buffer Entry

mfbhrbe RT, BHRBE

Reads a specific entry from the BHRB.

Encoding

Binary Layout

31

0:5

RT

6:10

BHRBE

11:15

/

16:20

302

21:30

/

31

 

Format X-form

Opcode 0x7C00025C

Extension Base

Operands

• RT
  Target
• BHRBE
  Entry Index

Example

mfbhrbe r3, 0

Registers Altered

BHRBE0:9

Related

More in Base

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Move the contents of a Branch History Rolling Buffer (BHRB) entry, indexed by BHRBE, into GPR RT. The BHRB records branch addresses and is used for performance monitoring. This is a hypervisor-privileged or performance-monitoring register operation. No architected status fields are affected.

Operation

RT ← BHRB[BHRBE]

Programming Note

The mfbhrbe instruction is used to access entries in the Branch History Rolling Buffer (BHRB). Ensure that the specified entry index is within the range of implemented entries to avoid placing zero in the target register. This instruction operates at user privilege level and does not generate exceptions under normal conditions.