Marc Santhoff wrote:
Am Dienstag, den 09.12.2008, 09:53 +0100 schrieb Marco van de Voort:
In our previous episode, Marc Santhoff said:
some small THUMB things, but FPC doesn't generate THUMB code).
One possible difference coming to my mind (although only a speed issue,
not influencing nonetheless working code):
There are some ARM7 (and maybe ARM9, not sure) core variants having no
hardware multiplication unit. IIRC the M in TDMI stands for "hardware
multiplier unit". Experiences with gcc showed me that the 32x32=64 mult
commands are not used in that case.
Wikipedia also calls ARM7 ARMV3 arch, and only ARM7TDMI ARMV4. This could be
the reason why. (and maybe the D and the I)
It would be nice to have the chance of setting some extra command line
arguments to the call to the assembler - I think that is what Riley is
is asking for.
The trick is that if you give FPC that info, it can check both code
generated and the assembler reader, and do the same AND provide a valid
source line. IOW, I don't see a good reason to do this in the backend
assembler, if it can be better done in the frontend.
Since I've been enlighted that I'm mistakenly ignored the fact that fpc
does the code generation and since ARM v4 is only mentioned on ARMs web
site as an ancient architecture mostly faded away I'm strongly with you:
http://www.arm.com/products/CPUs/architecture.html
Citation:
"ARMv4
The oldest version of the processor architecture supported today. All
previous versions are now obsolete. Implementations include some members
of the ARM7™ processor family and Intel StrongARM® processors. ARMv4 can
be considered a 32-bit ISA operating in a 32-bit address space."
Maybe, the fancy pictures on the ARM website concerning the ARM
architectures could lead to the assumption, that ARMv4 is mostly faded
away ;-) But this is not correct. A lot of ARM7 embedded controllers are
ARMv4 devices, including ATMEL AT91SAM7x, NXP LPC2x and STM STR7x. FPC
targets them perfectly. BTW the Openmoko Neo 1973 and Neo FreeRunner use
a Samsung S3C2442 (ARM9) which is ARMv4 too.
The compiler(s code generator) should take care of target cpu variants
and architectures.
I think, this would be a lot of work. Which architecture should be
implemented first? ARMv5 or better the latest ARMv7 (CORTEX) variants.
But what about the Thumb/Thumb-2 instruction set? Also very interesting.
From my point of view the current situation with FPC/ARM is pretty
good. And if someone really needs architecture specific implementations,
he could try to add these features to the compiler.
Regards, Bernd.
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