Register Usage Conventions - Xilinx MicroBlaze Reference Manual

Chapter 4: MicroBlaze Application Binary Interface

Register Usage Conventions

The register usage convention for MicroBlaze is given in
Table 4-2: Register Usage Conventions
R0
R1
R2
R3-R4
R5-R10
R11-R12
R13
R14
R15
R16
R17
R18
R19
R20
R21-R31
RPC
RMSR
REAR
RESR
RFSR
RBTR
REDR
RPID
RZPR
RTLBLO
RTLBHI
RTLBX
RTLBSX
RPVR0-
RPVR12
152
Send Feedback
Register Type Enforcement
Dedicated
Dedicated
Dedicated
Volatile
Volatile
Volatile
Dedicated
Dedicated
Dedicated
Dedicated
Dedicated
Dedicated
Non-volatile
Dedicated
or
Non-volatile
Non-volatile
Special
Special
Special
Special
Special
Special
Special
Special
Special
Special
Special
Special
Special
Special
www.xilinx.com
Table
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
Used for Service ID with attribute svc_table_handler
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
MicroBlaze Processor Reference Guide
4-2.
Purpose
UG081 (v14.7)