<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:12pt"><div>The only major issue is if you want to build for Thumb2 - you have to manually edit makefiles - because the full ARM cores support and startup files will choke the build process.<br><br>i.e. Building for Thumb2 with the freshly checked out subversion, when the compiler gets to compiling rtl/embedded/arm/lpc21x4.pp - it will choke because there are non-Thumb2 instructions in the boot code.<br><br>I just submitted a potential patch to the mailing list to switch the controllers arrays to structures - part of that patch has ifdef's in the controller files lpc21x4's and at91sam7x256's - so that when compiling for Thumb2 - the boot code for those controllers gets bypassed.<br><br>However, part of the confusion is that if you want Thumb2 RTL's - you have to append an extra option to Make process -
otherwise, the RTL will compile - but it will choke on real hardware.<br><br>There has been discussion on how the RTL should include every register for every machine - to make the user's life "easier." Yet - how easy is it to switch from Thumb2 to ARMV4 chips with the current setup ? In order to do that now, you need two different RTL's - via either separate compiles of the compiler - or different CFG files in the project directory (pointing to different system libraries).<br><br>If we are looking to save the user time by defining every peripheral register - why not save them time by not having to become a compiler expert ?<br><br>Again, these are my (sometimes random) thoughts on trying to make things easier for the end user. someone that wants to write controller code - not fitz with the compiler.<br><br>That said, school is starting - and I have a working compiler - so I am just as content to leave the status quo
be...<br><br>John<br><br></div><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><br><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><font size="2" face="Tahoma"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Jeppe Gręsdal Johansen <jjohan07@student.aau.dk><br><b><span style="font-weight: bold;">To:</span></b> FPC developers' list <fpc-devel@lists.freepascal.org><br><b><span style="font-weight: bold;">Sent:</span></b> Tue, August 23, 2011 7:42:51 PM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [fpc-devel] ARM vs Thumb2 - can't have both<br></font><br>
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Is it really that big a deal?<br>
<br>
I think the negatives outweigh the positives in the changes implied
here. Say what you want about the priciples about the instruction
sets(ARM and Thumb2), but they still share 95% of the backend code.<br>
<br>
When you're dealing with lowlevel targets like embedded arm you'll
still need to know the RTL code pretty well. The build system isn't
really very complex either. I personally see no reason to change the
way it is<br>
<br>
Den 23-08-2011 16:01, John Clymer skrev:
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<div>Digging some more around it today, came up with the
following idea...<br>
<br>
In the rtl/embedded folder - there is the "system" file for
"ARM" - it is ALL pascal - and compiles to either of Thumb2 or
ARMV4 - but not both.<br>
<br>
In that folder's Makefile.fpc, the units to be built are
listed - the could be switched to listing directories to get
built.<br>
<br>
One folder for ARMV4, one for Thumb2. A "system" file and
rtl.cfg file sits in each folder. The "system" file just
bounces back down and includes the current system files from
the rtl/embedded folder, but the library gets built in the
core specific folder.<br>
<br>
That's the easy part, the more difficult part will to be to
get the compiler to choose the correct system file. That is,
the "usual" ARM folder where the libraries sit would need to
have the same 2 seperate subdirectorie, the compiler would
have to choose which one based on the core it's currently
compiling for.<br>
<br>
John<br>
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<hr size="1"><b><span style="font-weight:bold;">From:</span></b>
David Welch <a rel="nofollow" class="moz-txt-link-rfc2396E" ymailto="mailto:dwelch@dwelch.com" target="_blank" href="mailto:dwelch@dwelch.com"><dwelch@dwelch.com></a><br>
<b><span style="font-weight:bold;">To:</span></b> FPC
developers' list <a rel="nofollow" class="moz-txt-link-rfc2396E" ymailto="mailto:fpc-devel@lists.freepascal.org" target="_blank" href="mailto:fpc-devel@lists.freepascal.org"><fpc-devel@lists.freepascal.org></a><br>
<b><span style="font-weight:bold;">Sent:</span></b> Tue,
August 23, 2011 10:39:50 AM<br>
<b><span style="font-weight:bold;">Subject:</span></b>
Re: [fpc-devel] ARM vs Thumb2 - can't have both<br>
</font><br>
<br>
Most if not all of my references to thumb meant the original
ARMv4T thumb instruction set, definitely not the thumb2
extensions, nor ARMv5 or ARMv6 extensions.<br>
<br>
If for example you had a thumb backend to fpc, you could
easily solve this problem, all of these libraries would run
on both platforms, one compiler, one set of libraries,
compiled one time.<br>
<br>
There is no thumb backend at the moment, this is the first
problem to that solution.<br>
<br>
I figure most folks would not want to sink to the lowest
common denominator.<br>
<br>
I would then recommend splitting the arm/arm7/ARMv4
architecture from the cortex-m3/ARMv7m, as implemented now
they are two incompatible instruction sets. One instruction
set happens to share the name of the company, move beyond
that sticking point and create two architectures.<br>
<br>
The third alternative is do what others do and build two
sets of libraries, one for each cpu type if that is the
preferred term to distinguish arm and thumb2. Even if they
are in the same library file but by name the linker extracts
the arm cpu whatsit function from the thumb2 cpu whatsit
function it is still two compilations of the whatsit
function.<br>
<br>
You really have to pick one of those solutions, same
instruction set or compile the libraries twice either as two
arches build one or the other but not both, or two cpus
within an arch and both/all cpus for an arch get built when
the arch compiler is built.<br>
<br>
David<br>
<br>
On 08/22/2011 01:15 AM, John Clymer wrote:<br>
> Yes, all my references of Thumb meant Thumb2.<br>
> <br>
<br>
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