Benoît Thébaudeau 19fd7a3551 Use additive offsets
OR-ing an offset to a base address instead of adding it is dangerous
because it can only work if the base address is aligned enough for the
offset.

Moreover, if the base address or the offset has a value unknown at
compile time, then the assembly instructions dedicated to 'base +
offset' addressing on most CPUs can't be emitted by the compiler because
this would require the alignment of the base address against the offset
to be known in order to optimize 'base | offset' into 'base + offset'.
In that case, the compiler has to emit more instructions in order to
compute 'base | offset' on most CPUs, e.g. on ARM, which means larger
binary size and slower execution.

Hence, replace all occurrences of 'base | offset' with 'base + offset'.
This must become a coding rule.

Here are the results for the cc2538-demo example:
 - Compilation of uart_init():
    * before:
        REG(regs->base | UART_CC) = 0;
        200b78:	f446 637c 	orr.w	r3, r6, #4032	; 0xfc0
        200b7c:	f043 0308 	orr.w	r3, r3, #8
        200b80:	2200      	movs	r2, #0
        200b82:	601a      	str	r2, [r3, #0]

    * now:
        REG(regs->base + UART_CC) = 0;
        200b7a:	2300      	movs	r3, #0
        200b7c:	f8c4 3fc8 	str.w	r3, [r4, #4040]	; 0xfc8

 - Size of the .text section:
    * before:	0x4c7c
    * now:	0x4c28
    * saved:	84 bytes

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
2015-03-28 17:28:15 +01:00
2015-03-28 17:28:15 +01:00
2015-02-22 16:39:49 +00:00
2015-03-10 15:33:58 +01:00
2015-02-25 13:16:27 +01:00
2015-02-25 13:16:27 +01:00
2013-03-26 23:15:37 +01:00
2013-03-26 23:15:37 +01:00

The Contiki Operating System

Build Status

Contiki is an open source operating system that runs on tiny low-power microcontrollers and makes it possible to develop applications that make efficient use of the hardware while providing standardized low-power wireless communication for a range of hardware platforms.

Contiki is used in numerous commercial and non-commercial systems, such as city sound monitoring, street lights, networked electrical power meters, industrial monitoring, radiation monitoring, construction site monitoring, alarm systems, remote house monitoring, and so on.

For more information, see the Contiki website:

http://contiki-os.org

Description
Contiki OS for 6502 based computers
Readme 75 MiB
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