gnupic: Re: [Sdcc-user] Adding PIC support to SDCC
Subject:
RE: [Sdcc-user] Adding PIC support to SDCC
From:
"Sandeep Dutta" ####@####.####
Date:
1 Sep 2000 16:43:07 -0000
Message-Id: <001901c01433$fd0932e0$cb18a9ce@ddi.com>
>Question 1:
>I think I know the answer, but why was SDCC created separate from gcc? My
guess
>is that even though gcc can be retargeted, it makes certain underlying
>assumptions which are invalid for microcontrollers.
Correct , SDCC addresses several issues which are microcontroller specific.
A) Many address spaces ( Most microcontrollers have multiple address spaces
accessable using different instructions). SDCC addresses this by adding
extra (target specific) keywords (so no kludgy intrinsics are needed).
Also
has three byte generic pointer.
B) Can operate entirely without stack. (Only function calls via pointers
cannot
be implemented). The local variables and parameters are assumed to be
"static"
and they can be overlayed for leaf functions.
>Question 2:
>Is SDCC `really' retargetable to a PIC? The underlying architecture of PICs
is
>entirely different than the 8051's. The major difference about which I'm
>concerned is the way the two handle stacks. The PIC (midrange family) has a
hard
>ware code stack that is 8 levels deep. There is no way for this stack to be
>accessed. Furthermore, there is no data stack. So consequently, there sre
no
>push/pop instructions. Does the intermediate code generator make
assumptions
>about the stack architecture?
See above.
>Question 3:
>Have there been any queries/requests of porting SDCC to the PIC before?
Want to do it .. no time :(...
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