Pierre Free Pascal wrote:
It is not closely following a specific abi, but for parameters
it works like this:
Up to 6 parameters are passed in registers $r4 to $r9,
others on the stack starting at offset 24 (=6*4).
(I had to adapt the 6 parameter very of linux/mips/syscall.inc
in order to get fpmmap to work).
The startup code of the function pushes these registers
back to the 6 4 byte slots from 0 to 24.
It sets $fp register ($r29 or $s8)
to the previous value of the $sp stack register.
This way, function parameters can be accessed by
offsets to $fp register, while locals or parameters
of function that will be called inside the function
are accessed via $sp register.
The biggest problem now is that GDB is not
pleased this, because it find that there is a frame register ($r29)
so that it computes falsely the address of all locals and arguments...
I think that we should add a list of all mips known ABI and
create a record that lists their specificities,
This way, we should be able to convert some constants
into ABI specific values.
I made a start at trying to get assembler and backend info into the
Wiki, my intention was to at least have URLs for the various ABIs. I
rather ground to a halt after getting examples of the assembler format
together for most targets, if anybody could contribute ABI stuff it
would be much appreciated.
http://wiki.lazarus.freepascal.org/Assembler_and_ABI_Resources
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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