Re: [Qemu-devel] [PATCH] host-pcc: enable building with -m32 or -m64

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

On 05/26/2011 03:14 PM, malc wrote:
> On Thu, 26 May 2011, Stefan Berger wrote:
>
>> With the below patch I can build either ppc (-m32) or ppc64 (-m64) versions of
>> Qemu (on a ppc64 host) when passing these compiler flags via 'configure ...
>> --extra-cflags="-m32"'.
>>
>> Signed-off-by: Stefan Berger<stefanb@linux.vnet.ibm.com>
>>
>> ---
>>   configure |    9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> Index: qemu-git/configure
>> ===================================================================
>> --- qemu-git.orig/configure
>> +++ qemu-git/configure
>> @@ -807,7 +807,14 @@ case "$cpu" in
>>       arm*)
>>              host_guest_base="yes"
>>              ;;
>> -    ppc*)
>> +    ppc)
>> +           QEMU_CFLAGS="-m32 $QEMU_CFLAGS"
>> +           LDFLAGS="-m32 $LDFLAGS"
>> +           host_guest_base="yes"
>> +           ;;
>> +    ppc64)
>> +           QEMU_CFLAGS="-m64 $QEMU_CFLAGS"
>> +           LDFLAGS="-m64 $LDFLAGS"
>>              host_guest_base="yes"
>>              ;;
>>       mips*)
>>
> This isn't right, if one has particular toolchain and wants to build
> something that defaults to a different bitlength he should be able to
> do that, this patch attempts to outsmart the defaults and furthermore
> prevents one from overriding the settings.
>
> P.S. host-pcc... pcc?
>
> P.P.S. On the ppc64 machine i have, gcc defaults to 32bit and for a
>         good reason - 64bit code is quite a bit slower when running
>         typical workloads (64bit guest not being one of them though)
>
Is it possible to change my ppc64 gcc compiler to produce 32bit binaries 
by default -- how? I'd like to test this case because for me not passing 
any parameters via --extra-cflags defaults to the ppc64 case above - 
obviously it will produce 64 bit binaries by default. -m32 then ends up 
in the ppc) case, -m64 again in the ppc64) case.

    Stefan