Register Usage Conventions - Xilinx MicroBlaze Reference Manual

Register Usage Conventions

The register usage convention for MicroBlaze is given in
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
or
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 (v2016.2) June 8, 2016
UG984 (v2016.1) April 6, 2016
Chapter 4: MicroBlaze Application Binary Interface
Enforcement
HW Value 0
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
HW Return address for Interrupt
SW Return address for Sub-routine
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
SW Reserved for storing a pointer to the Global Offset Table (GOT) in
Position Independent Code (PIC). Non-volatile in non-PIC 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
HW Exception Address Register
HW Exception Status Register
HW Floating Point Status Register
HW Branch Target Register
HW Exception Data Register
HW Process Identifier Register
HW Zone Protection Register
HW Translation Look-Aside Buffer Low Register
HW Translation Look-Aside Buffer High Register
HW Translation Look-Aside Buffer Index Register
HW Translation Look-Aside Buffer Search Index
HW Processor Version Register 0 through 12
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Table 4-2.
Purpose
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