On Tue, Aug 7, 2012 at 12:27 AM, James Brown <james.br...@alcolizer.com> wrote:
> Hi Everyone,
>
> I'm using an msp430f235 which has a 16x16 hardware multiplier but the
> msp430-gcc does not produce code to utilise the hardware multiplier,
> instead it generates a software multiply function.
>
> My final linker command looks like the following:
> /usr/bin/msp430-gcc -mmcu=msp430f235 -mmpy=16 -O2
> -Wa,-adhlns=output/S5S.elf -o output/S5S.elf output/.obj/Main.o
> output/.obj/SysConf.o output/.obj/System.o output/.obj/Version.o
> output/.obj/hw_io.o output/.obj/FCell.o
>
> I'm using the following gcc version from the arch linux distro
> msp430-gcc (mspgcc_20120406) 4.6.3 20120301 (mspgcc LTS 20120406 unpatched)
>
> What am I doing wrong? How do I get gcc to utilise the HW multiplier
> correctly (with interrupt disabling)?
You need to provide -mmcu=msp430f235 option both when compiling and linking.
You do not need to provide the -mmpy=16 option: any multiplier
available on an MCU is automatically defaulted to enabled when -mmcu
option is provided.
You do not need to specify any particular level of optimization.
mspgcc automatically disables interrupts around all multiplier
accesses, unless you provide the -mnoint-hwmul option in which case no
multiplier accesses are protected.
llc[27]$ cat /tmp/f.c
int domult (int a, int b) { return a * b; }
llc[28]$ msp430-gcc -S -Os -mmcu=msp430f235 /tmp/f.c
llc[29]$ cat f.s
.file "f.c"
.arch msp430f235
.cpu 430
.mpy 16se
.text
.p2align 1,0
.global domult
.type domult, @function
/***********************
* Function `domult'
***********************/
domult:
push r2
dint
nop
mov r15, &__MPYS
mov r14, &__OP2
mov &__RESLO, r15
pop r2
ret
.size domult, .-domult
.ident "GCC: (GNU) 4.7.0 20120322 (mspgcc dev 20120716)"
>
> Thanks,
> James
>
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