1 NOTES file for SDCC pic16 port
4 Current pic16 port status is: Development
6 Some things may change without notification between port updates. The latest
7 CVS snapshot is guarenteed to compile without problems, but does not
8 guarantee backwards compatibility.
10 For any questions please ask the current port
14 Raphael Neider <rneider AT web.de>
16 Other people to contact:
17 Vangelis Rokas <vrokas AT users.sourceforge.net>
18 Scott Dattalo <scott AT dattalo.com>
20 ======================================================================
21 ======================================================================
22 2005-Mar-23 Vangelis Rokas
23 1. I have added some optimizations that are controlled via enviroment
24 variables to allow checking. Later these will be either enabled globally
25 or controlled by command line options. The variables are:
26 a. OPTIMIZE_BITFIELD_POINTER_GET : optimizes bit field pointer reads
28 b. NO_REG_OPT : there is no register optimization performed by pCode
33 2004-Oct-29 Vangelis Rokas
34 1. Function parameters are passed now all via stack. This might
35 lower performance, but some issues are solved this way. Later
36 we can enable passing through WREG,PRODL,PRODH,FSR0L by implementing
40 2004-Sep-27 Vangelis Rokas
41 1. Function parameters have been extended to cover functions with
42 variable arguments. Now function parameters follow the rules below:
44 a) void foo(long a, int b, char c)
45 void foo(long a, int b, char c) reentrant
47 Stack layout: c, b+1, b, a+3, a+2, a+1 and WREG = a
49 b) prototype: void foo(long a, int b, ...)
51 example: foo(0xaaffeedd, 0xbbcc, 0x4455, 0x7788);
53 Stack layout: 0x77, 0x88, 0x44, 0x55, 0xbb, 0xcc, 0xaa, 0xff, 0xee, 0xdd
55 WREG is not used in functions with variable arguments so that the address
56 of the first parameter can be taken.
61 2004-Sep-24 Vangelis Rokas
62 1. Began implementation of generic pointers, current specs are:
63 0x0 xxxxxxx -> code pointer
64 0x8 xxxxxxx -> data pointer
65 0x4 xxxxxxx -> eeprom pointer (currently unimplemented)
68 2004-Aug-30 Vangelis Rokas
69 1. A few months ago Hans Dorn had the idea to support general pointer
70 for accessing all code, eeprom data and data ram memory. These pointers
71 would have 3 bytes of size (24-bits), of which only the 21 lower bits
72 would be useful. The rest of them could be used to indicate the pointer
74 0x4xxxxxxx would mean code pointer
75 0x8xxxxxxx would mean eeprom pointer
76 0xcxxxxxxx would mean data ram pointer
78 The implementatio of such pointers needs a lot of work and general
79 reform of pointer access, data initializing functions and the writing
80 of support functions for decoding their type.
82 The implementation of such pointers along with the implementation of
83 a more SDCC like stack access system will allow the writing of variable
84 arguments functions like printf etc... Also one set of functions will be
85 able to handle all data types without having to worry about where they
89 2004-May-23 Vangelis Rokas
91 1. The improvement of the port has been stalled a bit. But, struct/union
92 SFR headers are ready for the PIC18F[45][45][28] chips along with their
95 2. The genCmp function should be rewritten from scratch.
97 3. The internal helper functions for char/int/long/float arithmetic
98 now compile and will be placed in the appropriate directory under device/
102 2004-Feb-20 Vangelis Rokas
103 Major update with many bugfixes.
105 1. The most of the pic16 regression tests (former pic regression tests) pass
106 successfully. Many thanks to Hans Dorn who did a great job with the
107 arithmetic, shift and pointer functions.
109 2. Bit fields now work properly.
111 3. Stack is permanently enabled. Command argument -pstack-enable is deleted
112 and no more recognized by the port.
115 2004-Feb-07 Vangelis Rokas
117 1. Fixed a bug so that compiler allocated internal registered, will
118 be shared along multiple sources via '.registers' section placed
119 in absolute data memory address 0x0000. Registers 0x00 to 0x7f are
120 considered as internal since they can be used for fast access.
124 2004-Jan-11 Vangelis Rokas
127 The current release of the port can produce object code which is not
128 completely bug free. To use the new features the user should enable them via
129 command line arguments. A sane set of command arguments that I use to test
133 --debug enable sdcc debug information
134 --debug-xtra enable pic16 port debug information (most useful)
135 --debug-ralloc enable register allocator debug messages
136 --pcode-verbose enable verbose pcode generator messages
139 --pno-banksel disable banksel directives for the assembler
140 --pomit-config-words does not emit configuration instruction in
141 the translation This is useful when copmiling
142 multiple sources, when you do not want multiple
143 config instructions in the end file
144 --pomit-ivt disables the dumping of the interrupt vector tables
145 in the translation for the same reasons as above
146 --penable-stack enables stack support. This option uses stack to
147 pass function arguments, and reuses registers between
148 functions by saving the registers used in the function
152 --all-callee-saves you may omit this options as the port
153 enables it by default, all functions are currently
154 compiled as reentrant and they are marked as
156 --no-peep peephole optimizer is better to be switched off,
157 because it behaves strangely in some cases
158 --fommit-frame-pointer this omits frame pointer in functions that
159 don't use registers (maybe changed later, not
164 The current implementation puts every function in its own code section in
165 PIC's program memory. This may not be the standard, but I think its more
169 Since SDCC is goind for a release, its better to document pragmas available.
172 The 'code' pragma emits a function's code at a specific address in program
173 memory. Currently it is only used for functions.
175 #pragma code [function_name] [address]
178 The 'stack' pragma initializes the stack/frame pointer at an address of the
179 data ram other than the default (which is the end of the available data ram)
181 #pragma stack [address]
184 The 'maxram' pragma sets maximum data ram of the device. Currently is not
185 used at all, but it may be useful in the future when devices with external
186 memory will be supported.
188 #pragma maxram [max_address]
191 4. Internal compiler functions
192 Internal SDCC functions like, __fsmul, etc... are currently supported by the
193 port, but the libraries for the pic16 port are not yet ready. So one cannot
194 use long and float variables.
197 5. Special Function Registers (SFRs)
198 The processor SFRs are not anymore declared in any header file. The user can
199 define by himself all the needed SFR's. The code to that is:
201 sfr at [sfr_address] [sfr_name];
203 Where sfr_address is the SFR address in the data ram, and sfr_name is the
204 name of the SFR. i.e.: