Tool/software: TI C/C++ Compiler
If I have the following function:
extern unsigned short a, b;
extern unsigned long l;
void func(void)
{
l += a;
l -= b;
}
The the compiler produces the following incorrect output:
;*****************************************************************************
;* FUNCTION NAME: func *
;* *
;* Regs Modified : SP,SR,r15 *
;* Regs Used : SP,SR,r15 *
;* Local Frame Size : 0 Args + 0 Auto + 0 Save = 0 byte *
;*****************************************************************************
func:
;* --------------------------------------------------------------------------*
.dwcfi cfa_offset, 4
.dwcfi save_reg_to_mem, 16, -4
;** 7 ----------------------- l += a-b;
.dwpsn file "../src/longaddsub.c",line 7,column 5,is_stmt,isa 0
MOV.W &a+0,r15 ; [] |7|
SUB.W &b+0,r15 ; [] |7|
ADD.W r15,&l+0 ; [] |7|
ADDC.W #0,&l+2 ; [] |7|
;** ----------------------- return;
$C$DW$5 .dwtag DW_TAG_TI_branch
.dwattr $C$DW$5, DW_AT_low_pc(0x00)
.dwattr $C$DW$5, DW_AT_TI_return
RETA ; []
; []
.dwattr $C$DW$4, DW_AT_TI_end_file("../src/longaddsub.c")
.dwattr $C$DW$4, DW_AT_TI_end_line(0x09)
.dwattr $C$DW$4, DW_AT_TI_end_column(0x01)
.dwendentry
.dwendtag $C$DW$4
This result is incorrect because it calculates the difference of the two short values as a short value and then adds the result. Consider the case where `a=0` and `b=1`, then as written the result should be to subtract 1 from `l`, but as compiled it adds 65535 to `l` instead.
