[oe] [PATCH] cortex-m3: adjusted target cflags

[Mark Hatle]

On 2/7/11 1:33 PM, Khem Raj wrote:
> On Mon, Feb 7, 2011 at 7:53 AM, Enrico Scholz
> <enrico.scholz at sigma-chemnitz.de> wrote:
>> Explicit '-mthumb' is required because Cortex-M3 does not support ARM
>> instructions and actual flags cause gcc to fail with 'error: target CPU
>> does not support ARM mode'.
>>
>> The '-mcpu=cortex-m3' is shorter than '-march=armv7-m -mtune=cortex-m3'
>> and enables workarounds like '-mfix-cortex-m3-ldrd'.
> 
> Does -mcpu=cortex-m3 also cause gcc to tune for cortex-m3 ?

-mcpu=cortex-m3 is equivalent to -march=cortex-m3 -mtune=cortex-m3

So in this instance, it will have a side effect of potentially changing the
available set of instructions.. The existing command says the only available
instructions are those defined as "armv7-m", but I want to tune the instruction
scheduler for execution on "cortex-m3".

(I'm not an ARM expert, so I'm not sure what is reasonable in this case.. but
the arguments do have slightly different meanings.)

--Mark

>>
>> Signed-off-by: Enrico Scholz <enrico.scholz at sigma-chemnitz.de>
>> ---
>>  conf/machine/include/tune-cortexm3.inc |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/conf/machine/include/tune-cortexm3.inc b/conf/machine/include/tune-cortexm3.inc
>> index 6da9aee..a66a33c 100644
>> --- a/conf/machine/include/tune-cortexm3.inc
>> +++ b/conf/machine/include/tune-cortexm3.inc
>> @@ -1,4 +1,4 @@
>>  # valid options for -march: `armv7', `armv7-m'
>> -TARGET_CC_ARCH = "-march=armv7-m -mtune=cortex-m3 -mfpu=vfp -mfloat-abi=softfp"
>> +TARGET_CC_ARCH = "-mthumb -mcpu=cortex-m3 -mfpu=vfp -mfloat-abi=softfp"
>>  FEED_ARCH = "armv7"
>>  BASE_PACKAGE_ARCH = "armv7"
>> --
>> 1.7.4
>>
>>
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> 
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