[Icc-430] Suggestions on ICC Code improvement

[Wolfgang Schulze]

Sorry that I sent the same contents of the previous discussion
twice, but I thought I had the address wrong.

I did some more comparisons of the ICC code generated relative to the
IAR code. In some instances IAR is still better. Here are some more 
results. Hope they can be used by the programmer:


Comparison to a constant is done using a register, although it could be
done directly:

0490           ;   if (Uph_fi[0]>260) strcpy((char *)AnzStr,"L1 >260V ");
0490 3B400401          mov #260,R11
0494 1B900200          cmp _Uph_fi,R11
0498 0734              jge L42

It would be better to use
cmp _Uph_fi,#260
jge L42

Code of IAR
 \   000000   B2900501....         CMP.W   #0x105, &Uph_fi
 \   000006   0638                 JL      ??Verarb221_0

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When a function ends on a call and there is no pop , then it could
branch to the function. This saves code and time

Example

09AC           ;   Copy(ZweiteZeile,AnzStr);
09AC 3F400400          mov #_AnzStr,R15
09B0 3E400000          mov #_ZweiteZeile,R14
09B4 B0120000          call #_Copy
09B8                   .dbline -2
09B8           L175:
09B8                   .dbline 0 ; func end
09B8 3041              ret

Call #_Copy
ret
can be replaced by BR #_Copy

IAR Code

  764            Copy(ZweiteZeile,AnzStr);
 \                     ??Verarb71_1:
 \   000026   3E40....             MOV.W   #AnzStr, R14
 \   00002A   3C40....             MOV.W   #ZweiteZeile, R12
 \   00002E   3040....             BR      #Copy
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Registers are used when it would be possible to store directly:

0AF2           ;   AnzStr[n]=' ';
0AF2 3B400400          mov #_AnzStr,R11
0AF6 0A4E              mov R14,R10
0AF8 0A5B              add R11,R10
0AFA FA4020000000      mov.b #32,0(R10)

It would be better :
mov.b #32,#_AnzStr(R10)

IAR code

  828            AnzStr[n]=' ';
 \   00004E   FA402000....         MOV.B   #0x20, AnzStr(R10)

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We are always pushed for code space and would appreciate getting more
compact code (can't wait for the compatible 120k versions to be available).

We purchased the professional version but I have not understood the
method of global optimization yet. Is it done automatically during
compile and link time or must it be invoked manually. Some hints on
where to read about it would be appreciated.

Wolfgang