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

Mike Frysinger
2012-02-23T18:05:19Z

On Thursday 23 February 2012 12:49:59 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?

for things that require computation, yes. if it's just string values or other
variables, then it doesn't matter and avoiding ":=" is preferred.
-mike
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