Register Usage Conventions - Xilinx MicroBlaze Reference Manual

Register Usage Conventions

The register usage convention for MicroBlaze is given in the following table.
Table 4-2: Register Usage Conventions
Register Type
R0 Dedicated
R1 Dedicated
R2 Dedicated
R3-R4 Volatile
R5-R10 Volatile
R11-R12 Volatile
R13 Dedicated
R14 Dedicated
R15 Dedicated
R16 Dedicated
R17 Dedicated
R18 Dedicated
R19 Non-volatile
R20 Dedicated
Non-volatile
R21-R31 Non-volatile
RPC Special
RMSR Special
REAR Special
RESR Special
RFSR Special
RBTR Special
REDR Special
RPID Special
RZPR Special
RTLBLO Special
RTLBHI Special
RTLBX Special
RTLBSX Special
RPVR0-12 Special
MicroBlaze Processor Reference Guide
UG984 (v2018.2) June 21, 2018
Enforcement
Value 0
HW
SW Stack Pointer
SW Read-only small data area anchor
SW Return Values/Temporaries
SW Passing parameters/Temporaries
SW Temporaries
SW Read-write small data area anchor
Return address for Interrupt
HW
Return address for Sub-routine
SW
HW Return address for Trap (Debugger)
HW/SW Return address for Exceptions
HW, if configured to support hardware exceptions, else SW
SW Reserved for Assembler/Compiler Temporaries
SW Must be saved across function calls. Callee-save
Reserved for storing a pointer to the global offset table (GOT)
SW
in position independent code (PIC). Non-volatile in non-PIC
or
code. Must be saved across function calls. Callee-save.
SW Must be saved across function calls. Callee-save.
HW Program counter
HW Machine Status Register
Exception Address Register
HW
Exception Status Register
HW
HW Floating-Point Status Register
HW Branch Target Register
HW Exception Data Register
HW Process Identifier Register
HW Zone Protection Register
Translation Look-Aside Buffer Low Register
HW
Translation Look-Aside Buffer High Register
HW
HW Translation Look-Aside Buffer Index Register
HW Translation Look-Aside Buffer Search Index
HW Processor Version Register 0 through 12
www.xilinx.com
Chapter 4: MicroBlaze Application Binary Interface
Purpose
187
Send Feedback