URL: <https://savannah.nongnu.org/bugs/?66044>
Summary: core->dataAddressMask not applied correctly
Group: Simulavr: an AVR simulator
Submitter: gjlayde
Submitted: Wed 31 Jul 2024 10:36:58 AM UTC
Category: Simulation
Severity: 3 - Normal
Item Group: None
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Component Version: simulavr
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Follow-up Comments:
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Date: Wed 31 Jul 2024 10:36:58 AM UTC By: Georg-Johann Lay <gjlayde>
In the code for ATtiny2313 below, the content of the XH register should be
ignored (masked out) when X is used to access RAM (or more generally, data in
the RAM address space, which extends from address 0 to 223).
However, XH is not ignored so that the code below runs into my_abort:
;;; avr-gcc foo.sx -o foo.elf -mmcu=attiny2313
;;; simulavr -d attiny2313 -f foo.elf -a 0x20 -e 0x21 -M
.data
var:
.byte 123
.global __do_copy_data
.text
.global main
main:
ldi XL, lo8(var)
;; Write garbage to XH which is in order for ATtiny2313:
;; That device has RAM_size = 128 and IO_space = 64,
;; which makes a valid RAM address range of 0...223, and hence a
;; core->dataAddressMask of 0xff. This means that when simulavr is
masking the
;; address in X for access, the XH part will be masked out entirely.
;; On the instruction level this means that it is sufficient to
;; specify the lo8 part of an address for indirect RAM accesses.
ldi XH, 1
ld r16, X
cpi r16, 123
brne my_abort
my_exit:
out 0x1, r0
my_abort:
out 0x0, r0
ret
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