#1423 Invalid subtraction code

[Don Wooton]

I have found a condition where sdcc is generating invalid code for 32 bit subtraction.

I am compiling for -mpic14 -p16f877a

I tested with sdcc source taken from svn on 16-Sep-07 and again with source taken from svn on 21-Jan-08 and get the same results.

$ sdcc -v
SDCC : mcs51/gbz80/z80/avr/ds390/pic16/pic14/TININative/xa51/ds400/hc08 2.7.4 #4996 (Jan 21 2008) (UNIX)

The simulator and the real PIC seem to get the same results.

For the errCase() routine the result of
(5000 - 1) is 4743
(0x00001388 - 0x00000001) is 0x00001287

For the okCase() routine the result of
(5000 - 1) is 4999
(0x00001388 - 0x00000001) is 0x00001387

Is this a known problem?

I have changed my code to use the volatile workaround shown in okCase().

- Don

[Don Wooton]

Source, Makefile and asm

[Raphael Neider]

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Hi Don,

the problem was not known (to me), but by now it is history: I have just committed a fix for this as SDCC r5066.
I feel that besides the fixed subtraction, also the addition code generator needs some maintenance, so there will probably soon (just before the upcoming code freeze or after the release) be another update.

Thank you for reporting the problem!

Regards,
Raphael