Setting build parameters for a sub-tree of RTEMS sources

[Ralf Corsepius]

"John M. Mills" wrote:
> 
> Nick,
> 
> On Mon, 24 Apr 2000 Nick.SIMON at syntegra.bt.co.uk wrote:
> > 'Fraid I don't know the answer to John's question, but I'm most concerned
> > about problems with 'volatile' - can anyone shed any light on this?
> 
> I don't know how general might be the problems, but the specifics are:

> 2) I am staying close to Ralf Crosepius' SH-1 BSP, which provides macro
>    to read and write on-chip register. For example:
>    'c/src/exec/score/cpu/sh/rtems/score/sh_io.h' defines:
> '#define read8(addr)  (*(volatile unsigned8 *) (addr))'
> 
> so a line like:
>    'temp8 = read8(SOME_ONCHIP_REG);' should try to read the named byte.
> 
FWIW: Similar constructs are used for Linux on almost any architecture
Linux supports (cf include/asm-*/io.h in Linux-2.2). They should be save
when being used with constants and ordinal types.

>
> I found the problem with enabling serial output, but I must assume it
> could be affecting my other hardware setup routines.

I am inclined to agree, because comparing the -O1 and -O4 compiled
assembly code of your hw_init.c doesn't show anything obvious:

Here is the relevant excerpt of 'diff hw_init.s-O1 hw_init.s-O4'
 _bsp_hw_init:
        mov.l   r14, at -r15
-       mov     r15,r14
        mov.w   L54,r3
        mov.w   @r3,r1
-       extu.w  r1,r1
        mov.w   L55,r2
+       extu.w  r1,r1
        or      r2,r1
        mov.w   r1, at r3
        mov.w   L56,r2
@@ -30,6 +21,7 @@
        extu.w  r1,r0
        or      #32,r0
        mov.w   r0, at r2
+       mov     r15,r14
        mov     r14,r15
        rts
        mov.l   @r15+,r14

The diff this fragment was taken from, was generated this way (using the
hw_init.c you posted in reply to Joel):

cd <build>/c/gensh2/lib/libbsp/sh/gensh2/startup

rm o-optimize/hw*
make CFLAGS=--save-temps CFLAGS_OPTIMIZE_V=-O1
mv hw_init.s hw_init.s-O1

rm o-optimize/hw*
make CFLAGS=--save-temps CFLAGS_OPTIMIZE_V=-O4
mv hw_init.s hw_init.s-O4

diff -u hw_init.s-O1 hw_init.s-O4

BTW: This should answer your initial question, too.

Ralf

-- 
Ralf Corsepius 
Forschungsinstitut fuer Anwendungsorientierte Wissensverarbeitung (FAW)
Helmholtzstr. 16, 89081 Ulm, Germany     Tel: +49/731/501-8690
mailto:corsepiu at faw.uni-ulm.de           FAX: +49/731/501-999  
http://www.faw.uni-ulm.de