this is a strcpy trick --
if gcc knows that data are world aligned, it uses word operation.
if it does not -- byte ones.
Alignment of FieldDevices[] isn't known at the compile time as follows from
your example.
~d
On Friday 06 August 2004 13:10, Hardy Griech wrote:
> Hi,
>
> when Dmitry announced the strict align patch he stated that 'Thes forces
> all local data be aligned at the word boundary.'
>
> Dispite his statement, it seems to me that the struct layout is not
> being changed. Instead the word access is split into two byte accesses:
>
> With strict align:
>
> mov.b #llo(11), &HartDevicesM$FieldDevices+2
> mov.b #llo(22), &HartDevicesM$FieldDevices+3
> mov.b #llo(33), &HartDevicesM$FieldDevices+4
> mov.b #llo(44), &HartDevicesM$FieldDevices+5
> mov.b #llo(55), &HartDevicesM$FieldDevices+6
> mov.b 2(r8), &HartDevicesM$FieldDevices+7
> mov.b 3(r8), &HartDevicesM$FieldDevices+8
>
>
> Without
>
> mov.b #llo(11), &HartDevicesM$FieldDevices+2
> mov.b #llo(22), &HartDevicesM$FieldDevices+3
> mov.b #llo(33), &HartDevicesM$FieldDevices+4
> mov.b #llo(44), &HartDevicesM$FieldDevices+5
> mov.b #llo(55), &HartDevicesM$FieldDevices+6
> mov 2(r8), &HartDevicesM$FieldDevices+7
>
> (which is wrong code). The struct looks like this:
>
> struct fielddevice {
> enum BUFFSTATES state;
> uint8_t unid[5];
> uint16_t originaddr;
> uint16_t parentaddr;
> uint8_t unansweredCmds;
> uint8_t hopCnt;
> uint16_t timer5;
> TOS_StatusMsg values;
> } __attribute__ ((packed)) FieldDevices[FIELDDEVS];
>
> Anyway to force correct alignment of words (even with patch) witout
> changing the source code?
>
> Hardy
>
>
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