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Need help tracing an assembly call

 
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Grimmtooth



Joined: 16 Jul 2009
Posts: 5

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Need help tracing an assembly call
PostPosted: Fri Aug 07, 2009 6:44 pm     Reply with quote
I'm looking to trace the c compiler's assembly structures and calls to look for speed optimization opportunities. Unfortunately, I have yet to figure out how to trace calls like the one that follows:

Code:
00848:  BCLR.B  43.0
0084A:  MOV     W6,W0
0084C:  MOV     W7,W1
0084E:  MOV     #100,W2
00850:  MOV     #0,W3
00852:  CALL    32A
00856:  ADD     W0,[W5],[W5]
00858:  ADDC    W1,[++W5],[W5]


Is there a way to search for the assembly call to 32A or find it manually? Initially, I thought it was a call to a program address, having run a search, I found that is not the case.

Anyone have suggestions how I can trace the compiler function call?
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Aug 07, 2009 7:03 pm     Reply with quote
To see the all the ASM code for the program in the .LST file, you need to
comment out the #nolist statement at the start of the .H file for your PIC.
Example:
Quote:

//////// Standard Header file for the PIC18F452 device /////////
#device PIC18F452
//#nolist

Then re-compile and look for your routine again.
Grimmtooth



Joined: 16 Jul 2009
Posts: 5

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PostPosted: Mon Aug 10, 2009 12:36 pm     Reply with quote
I'm using a pic24f and my header is as follows:

Code:
#include <24FJ128GA010.h>

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES NOJTAG                   //JTAG disabled
#FUSES NOPROTECT                //Code not protected from reading
#FUSES NOWRT                    //Program memory not write protected
#FUSES DEBUG                    //Debug mode for use with ICD
#FUSES NOCOE                    //Device will reset into operational mode
#FUSES ICSP2                    //ICD uses PGC2/PGD2 pins
#FUSES NOWINDIS                 //Watch Dog Timer in Window mode
#FUSES WPRES128                 //Watch Dog Timer PreScalar 1:128
#FUSES WPOSTS16                 //Watch Dog Timer PostScalar 1:32768
#FUSES IESO                     //Internal External Switch Over mode enabled
#FUSES PR_PLL                   //Primary Oscillator with PLL
#FUSES NOCKSFSM                 //Clock Switching is disabled, fail Safe clock monitor is disabled
#FUSES NOOSCIO                  //OSC2 is clock output
#FUSES XT                       //Crystal osc <= 4mhz for PCM/PCH , 3mhz to 10 mhz for PCD

#use delay(clock=32000000)


I didn't see a #nolist preprocessor command on the list. Is this a default functionality that I need disable? Also, the assembly I am looking for is not a user-defined function, but a compiler called function used to compile a loop written in c. I am just trying to verify how it implemented the program from c.
PCM programmer



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Posts: 21708

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PostPosted: Mon Aug 10, 2009 12:53 pm     Reply with quote
I don't have the PCD compiler, but in PCB, PCM, and PCH, the #nolist
line would be near the top of the .h file for PIC. Look in this file:
Quote:
24FJ128GA010.h
Grimmtooth



Joined: 16 Jul 2009
Posts: 5

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PostPosted: Mon Aug 10, 2009 5:44 pm     Reply with quote
I was able to track down the nolist command and comment it out, but it didn't change the call structure of the compiler. For example, the c expression here in assembly has 2 calls to functions, but I can't find anything relating to call 22E or call 32A.

Is there a way to single step through the assembly code instead of the c code? If so, perhaps I can follow the trace that way.

Code:
....................             data[a]-=(21*data[b]+11)/64;
0073E:  MOV     A96,W4
00740:  MUL.UU  W4,#4,W0
00742:  MOV     #862,W4
00744:  ADD     W0,W4,W5
00746:  MOV     A98,W4
00748:  MUL.UU  W4,#4,W0
0074A:  MOV     #862,W4
0074C:  ADD     W0,W4,W0
0074E:  MOV     W0,W4
00750:  MOV     #0,W3
00752:  MOV     [W4++],[W3++]
00754:  MOV     [W4++],[W3++]
00756:  MOV     W0,W2
00758:  MOV     W1,W3
0075A:  MOV     #15,W0
0075C:  MOV     #0,W1
0075E:  CALL    22E
00762:  MOV.D   W0,W6
00764:  ADD     W6,#B,W6
00766:  ADDC    W7,#0,W7
00768:  BCLR.B  43.0
0076A:  MOV     W6,W0
0076C:  MOV     W7,W1
0076E:  MOV     #40,W2
00770:  MOV     #0,W3
00772:  CALL    32A
00776:  MOV     [W5],W4
00778:  SUB     W4,W0,[W5]
0077A:  MOV     [++W5],W4
0077C:  SUBB    W4,W1,[W5]
PCM programmer



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Posts: 21708

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PostPosted: Mon Aug 10, 2009 5:51 pm     Reply with quote
What happens if you load the .LST file and do a search for that address ?
Do you see it ?

If not, in MPLAB, go to the View menu and look at the Disassembly listing
and/or the Program Memory window.

If the code is actually there, you'll at least see it in the Program Memory
window.

However, I don't have the PCD compiler, so I can't verify this for myself.
This advice is based on the PCM and PCH compilers.
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