Subject:
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Re: GCC vs. IAR compiler: Could GCC be tweaked to generate code as tight as IAR?
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Newsgroups:
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lugnet.robotics.nxt.nxthacking
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Date:
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Wed, 14 Mar 2007 21:45:20 GMT
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Viewed:
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17335 times
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In lugnet.robotics.nxt.nxthacking, John Hansen wrote:
> In lugnet.robotics.nxt.nxthacking, John Hansen wrote:
> > In lugnet.robotics.nxt.nxthacking, Rasmus Pedersen wrote:
> > > Hi,
> > >
> > > If I compile the LEGO firmware sources with gcc, the code size increases much
> > > beyond the 128 KB (which I think) the IAR compiled sources fits into. That means
> > > that one have to relocate part of the compiled code into the memory areas
> > > between 128KB-256KB. That is ok, but not totally optimal as the files,
> > > filehandles, and file verion info is also in that region making it a puzzle.
> > > Also I think it is hard to download new files if the flash is partly taken for
> > > code purposes.
> >
> > Are you adjusting these values in d_loader.h?
I did not do so. The memory map in LEGO_MINDSTORMS_NXT_Firmware_v1.03.bin is
like this for the files:
0x11F000-0x12E99D Actual files like Demo.rxe
0x13FF00-0x13FF37 FILE_HANDLE(s)
0x13FFFC-0c13FFFF FILEVERSION
The nxtgcc stuff compiles to 126176 bytes in the .text segment just fits below
STARTOFUSERFLASH (800 byte margin). The next segment .text2 + .data is 29752
bytes and is linked in at 0x138700. So it ends up pretty close (968 bytes) from
the FILE_HANDLE(s) address.
Anyway, if IAR compiles to 121324 bytes then the converted version of the
sources is 126176+23572+6180 - 121324 = 34604 bytes larger. However, I looked in
LEGO_MINDSTORMS_NXT_Firmware_v1.03.bin and it seems like the firmware code ends
at 0x1E226, which is 123436 bytes. Do you know why there is a difference between
your compiler and the one producing the firmware?
How are the file tables generated with the IAR compiler? Is there a tool for
that? I cut (with a little utility called binsert) the three file related memory
ranges out of LEGO_MINDSTORMS_NXT_Firmware_v1.03.bin and indsert them in the gcc
compiled image:-).
> >
> > #define STARTOFFILETABLE (0x13FF00L)
> > #define STARTOFUSERFLASH (0x11F000L)
> > #define SIZEOFUSERFLASH (STARTOFFILETABLE - STARTOFUSERFLASH)
> >
> > I've been told by folks at LEGO that if I grow the size of the firmware by
> > adding new features that I will need to modify these values. And the boundary
> > needs to be divisible by 8.
>
>
> More precisely, I was told to increase the STARTOFUSERFLASH value if I increased
> the firmware size beyond the current value. The unmodified source code compiles
> to 121324 bytes using the current evaluation version of the IAR Embedded
> Workbench (4.41.1.201). The STARTOFUSERFLASH is 0x1F000 which is 126976. That
> means with IAR we have about 5652 bytes to play with before it will be necessary
> to increase the STARTOFUSERFLASH value.
I should try that one day and see if it can be avoided to split the code into
.text and .text2. Good hint.
Best,
Rasmus
>
> John Hansen
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