[U-Boot] [PATCH v2 3/5] ARM: enable Thumb build

[Aneesh V]

On Thursday 23 February 2012 11:21 PM, Tom Rini wrote:
> On Thu, Feb 23, 2012 at 11:19:59PM +0530, Aneesh V wrote:
>> On Thursday 23 February 2012 11:04 PM, Tom Rini wrote:
>>> On Thu, Feb 23, 2012 at 10:58:36PM +0530, Aneesh V wrote:
>>>> On Thursday 23 February 2012 08:27 PM, Mike Frysinger wrote:
>>>>> On Thursday 23 February 2012 08:39:43 Aneesh V wrote:
>>>>>> --- a/arch/arm/config.mk
>>>>>> +++ b/arch/arm/config.mk
>>>>>>
>>>>>> -# Explicitly specifiy 32-bit ARM ISA since toolchain default can be
>>>>>> -mthumb: +# Choose between ARM/Thumb instruction sets
>>>>>> +ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
>>>>>> +PF_CPPFLAGS_ARM := $(call cc-option, -mthumb -mthumb-interwork,\
>>>>>> +			$(call cc-option,-marm,)\
>>>>>> +			$(call cc-option,-mno-thumb-interwork,)\
>>>>>> +		)
>>>>>> +else
>>>>>>   PF_CPPFLAGS_ARM := $(call cc-option,-marm,)
>>>>>> +PF_CPPFLAGS_ARM += $(call cc-option,-mno-thumb-interwork,)
>>>>>
>>>>> this 2nd part is no good.  "+=" is not the same thing as ":=".
>>>>
>>>> I don't understand the difference. '+=' is done after ':=' right?
>>>
>>> '+=' is evaluated every file we build, ':=' is evaluated once.  We use
>>> the latter to keep build times down.
>>>
>>
>> Ok. so, are we trying to reduce the number of "+=", right?
>
> Yes, it should already be at or near 0 uses.

We need at least one for finally appending to the exported variable,
right. So, looks like one += for adding '-mthumb -mthumb-interwork'
together is better than having one each for the two options? Is that
the logic?