Hi, I believe I have a fix for all issues you reported: - useless MOVFF x,x removed (in this particular situation -- there may be more situations like this) - missing BANKSEL added (incorrect removal was caused by the useless MOVFF, because it used an operand that -- if we had a BANKSEL for it -- would have made the missing one obsolete. For MOVFF operands, we have no BANKSEL, so this was a bug) - MOVF a, W; MOVWF a turned to MOVFF (this can be better, if a is not used before/afterwards and if a is not known to be already in W; it can be worse if a is used again (copied somewhere else) or if it's already in W)
Patch attached. If anyone wants to review it -- you are welcome. Esp. the
SPIL_LOC && IS_TEMP is something I do not really understand -- it works for
our situation, but I am not sure how correct / generally applicable that is
:-(.
I'll try to dig into this again tonight and check it in around 23:00 CEST
today.
Good night,
Raphael
2016-08-29 15:33 GMT+02:00 Kustaa Nyholm <kustaa.nyh...@planmeca.com>:
> Here is a minimal self contained test case that produces the problem:
>
>
> //------------------------------------------
> typedef struct {
> char member;
> } test_type;
>
> extern test_type g_test1[];
> extern test_type g_test2;
>
> void foobar() {
> g_test2.member = g_test1[0].member;
> g_test2.member = g_test1[0].member;
> }
> //------------------------------------------
>
>
> generated code:
>
>
> //------------------------------------------
> 01008 S_main__foobar code
> 000000 01009 _foobar:
> 01010 ; .line 66; main.c g_test2.member
> = g_test1[0].member;
> 000000 CFD9 FFE5 01011 MOVFF FSR2L, POSTDEC1
> 000004 CFE1 FFD9 01012 MOVFF FSR1L, FSR2L
> 01013 ; .line 67; main.c }
> 000008 C??? F??? 01014 MOVFF _g_test1, _g_test1
> 00000C ???? 01015 BANKSEL _g_test1
> 00000E 51?? 01016 MOVF _g_test1, W, B
> 000010 ???? 01017 BANKSEL _g_test2
> 000012 6F?? 01018 MOVWF _g_test2, B
> 01019 ; .line 68; main.c
> 000014 C??? F??? 01020 MOVFF _g_test1, _g_test1
> 000018 51?? 01021 MOVF _g_test1, W, B
> 01022 ; removed redundant BANKSEL
> 00001A 6F?? 01023 MOVWF _g_test2, B
> 00001C CFE4 FFD9 01024 MOVFF PREINC1, FSR2L
> 000020 0012 01025 RETURN
> //------------------------------------------
>
>
>
> compiled with:
>
> //------------------------------------------
> /Users/nyholku/sdcc-3.6.0/bin/sdcc --no-crt --ivt-loc=0x800 -V -L
> /Users/nyholku/sdcc-3.4.0/share/sdcc/non-free/lib/pic16 -Wa,-S,0
> -Wl,-m,-s18f45k50.lkr -mpic16 -p18f45k50 --disable-warning 85 --std-sdcc99
> --obanksel=3 --use-non-free main.c
> //------------------------------------------
>
> Thinking this through while the code would work with without the BANKSEL
> optimisation,
> it would of course be preferable if the assignment would be optimised to a
> single MOVFF instruction.
> And I think (without knowing the details of code generation or peephole
> optimisation)
> that this should be easy to do because the compiler at that point knows
> both the source
> and destination absolute (even if symbolic) addresses.
>
> wbr Kusti
>
>
>
>
>
>
>
>
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fixes.patch
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