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bennyboos
Joined: 17 Nov 2005
Posts: 30
Location: Chester UK
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| Unnecessary overhead by Compiler |
 Posted: Fri Jun 09, 2006 3:22 am |
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I have noticed that the compiler occasionaly inserts additional code that in some instances is useless or in my case unwanted because I want to keep things as compact as possible (i.e. a bootloader).
For example, the following code
| Code: | #include <16F819.h>
void main(void) {
setup_adc_ports(ALL_ANALOGS);
while(1) restart_wdt();
} |
produces the following (dis)assembly
| Code: | --- C:\Hiykon\Genial\Ccode\HarvesterMk2\PumpBoard-PIC16F819-Boot\Version2\main.c ---------------
1: #include <16F819.h>
000 3000 MOVLW 0
001 008A MOVWF 0xa
002 2804 GOTO 0x4
003 0000 NOP
2:
3: void main(void) {
004 0184 CLRF 0x4
005 301F MOVLW 0x1f
006 0583 ANDWF 0x3, F
007 1683 BSF 0x3, 0x5
008 141F BSF 0x1f, 0
009 149F BSF 0x1f, 0x1
00A 151F BSF 0x1f, 0x2
00B 119F BCF 0x1f, 0x3
00C 1283 BCF 0x3, 0x5
4: setup_adc_ports(ALL_ANALOG);
00D 1683 BSF 0x3, 0x5
00E 101F BCF 0x1f, 0
00F 109F BCF 0x1f, 0x1
010 111F BCF 0x1f, 0x2
011 119F BCF 0x1f, 0x3
012 1283 BCF 0x3, 0x5
5: while(1) restart_wdt();
013 0064 CLRWDT
014 2813 GOTO 0x13
015 0063 SLEEP |
From line 007-00C the compiler sets all of the ADC ports to digital without my asking it. While this might be regarded as convenient it seems a bit wasteful since in this example, the first thing I wish to do is set them all to analog.
Does anyone know a way or option setting to stop the compiler being too helpful (wasteful)?
Bennyboos |
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Douglas Richard
Joined: 08 Sep 2003
Posts: 49
Location: Concord NH
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| reply Unnecessary overhead by Compiler |
| Posted: Fri Jun 09, 2006 6:14 am |
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| set up your analog ports manually. That is instead of using setup_adc_ports(), locate the SFR needed and manipulate them yourself. Saves code but not very portable. |
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bennyboos
Joined: 17 Nov 2005
Posts: 30
Location: Chester UK
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| Unnecessary overhead by Compiler |
| Posted: Fri Jun 09, 2006 6:40 am |
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Hi Doug,
I've already tried this method but the compiler still insists on setting bits in adcon1 before it gets as far as my C-code.
E.G.
| Code: | #include <16F819.h>
#byte adcon1 = 0x9F
void main(void) {
adcon1 &= 0xF0;
while(1) restart_wdt();
} |
Produces the following disassembly
| Code: | --- C:\Hiykon\Genial\Ccode\HarvesterMk2\PumpBoard-PIC16F819-Boot\Version2\main.c ---------------
1: #include <16F819.h>
000 3000 MOVLW 0
001 008A MOVWF 0xa
002 2804 GOTO 0x4
003 0000 NOP
2:
3: #byte adcon1 = 0x9F
4: void main(void) {
004 0184 CLRF 0x4
005 301F MOVLW 0x1f
006 0583 ANDWF 0x3, F
007 1683 BSF 0x3, 0x5
008 141F BSF 0x1f, 0
009 149F BSF 0x1f, 0x1
00A 151F BSF 0x1f, 0x2
00B 119F BCF 0x1f, 0x3
00C 1283 BCF 0x3, 0x5
5: adcon1 &= 0xF0;
00D 30F0 MOVLW 0xf0
00E 1683 BSF 0x3, 0x5
00F 059F ANDWF 0x1f, F
010 1283 BCF 0x3, 0x5
6: while(1) restart_wdt();
011 0064 CLRWDT
012 2811 GOTO 0x11
013 0063 SLEEP |
i.e. we still seem to have lines 007 to 00C which are totally unnecessary.
There also seems to a lot of wasted fiddling of bank select???
Ben |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Re: Unnecessary overhead by Compiler |
| Posted: Fri Jun 09, 2006 7:09 am |
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| bennyboos wrote: | Hi Doug,
I've already tried this method but the compiler still insists on setting bits in adcon1 before it gets as far as my C-code.
E.G.
| Code: | #include <16F819.h>
#byte adcon1 = 0x9F
void main(void) {
adcon1 &= 0xF0;
while(1) restart_wdt();
} |
Produces the following disassembly
| Code: | --- C:\Hiykon\Genial\Ccode\HarvesterMk2\PumpBoard-PIC16F819-Boot\Version2\main.c ---------------
1: #include <16F819.h>
000 3000 MOVLW 0
001 008A MOVWF 0xa
002 2804 GOTO 0x4
003 0000 NOP
2:
3: #byte adcon1 = 0x9F
4: void main(void) {
004 0184 CLRF 0x4
005 301F MOVLW 0x1f
006 0583 ANDWF 0x3, F
007 1683 BSF 0x3, 0x5
008 141F BSF 0x1f, 0
009 149F BSF 0x1f, 0x1
00A 151F BSF 0x1f, 0x2
00B 119F BCF 0x1f, 0x3
00C 1283 BCF 0x3, 0x5
5: adcon1 &= 0xF0;
00D 30F0 MOVLW 0xf0
00E 1683 BSF 0x3, 0x5
00F 059F ANDWF 0x1f, F
010 1283 BCF 0x3, 0x5
6: while(1) restart_wdt();
011 0064 CLRWDT
012 2811 GOTO 0x11
013 0063 SLEEP |
i.e. we still seem to have lines 007 to 00C which are totally unnecessary.
There also seems to a lot of wasted fiddling of bank select???
Ben |
Remember that C is not as compact and ASM. Some things you will just have to live with. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Jun 09, 2006 11:42 am |
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I don't think there is a way to prevent the compiler from inserting
the startup code, in which it sets Port A to all digital i/o. What is
needed, is something like a #build(noinit) statement. This would
stop the compiler from adding any init code to main(). Someone
would have to send a request to CCS and ask them to add this.
With respect to the inefficient method of initializing the ADCON register,
CCS started doing this in late 2003. Before that time, they used to
init ADCON with one byte-wide instruction. I sent one or more emails
to them complaining about it, but they ignored them all.
http://www.ccsinfo.com/forum/viewtopic.php?t=19616 |
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Ttelmah
Guest
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| Posted: Fri Jun 09, 2006 2:44 pm |
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There is a 'trick', if you have PCW. Just use the device editor, and set the number of ADC channels to '0'. The compiler then no longer generates the ADC initialisation code. The listing file (with the manual setting of adcon1), becomes:
| Code: |
0000: MOVLW 00
0001: MOVWF 0A
0002: GOTO 004
0003: NOP
.................... #include <16F819.h>
.................... //////// Standard Header file for the PIC16F819 device ////////////////
.................... #device PIC16F819
.................... #list
....................
....................
.................... #byte adcon1 = 0x9F
....................
.................... void main(void) {
0004: CLRF 04
0005: MOVLW 1F
0006: ANDWF 03,F
.................... adcon1 &= 0xF0;
0007: MOVLW F0
0008: BSF 03.5
0009: ANDWF 1F,F
.................... while(1) restart_wdt();
000A: CLRWDT
000B: GOTO 00A
.................... }
000C: SLEEP
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Brute force, but it does work!...
Best Wishes |
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