Re: Preliminary 'wip-armhf' branch pushed

[John Darrington <john@darrington.wattle.id.au>]

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On Thu, Jan 01, 2015 at 01:22:53PM -0500, Mark H Weaver wrote:
     John Darrington <john@darrington.wattle.id.au> writes:
     
     > On Thu, Jan 01, 2015 at 02:11:19AM -0500, Mark H Weaver wrote:
     >      John Darrington <john@darrington.wattle.id.au> writes:
     >      
     >      >      * You patched gcc/config/arm/linux-eabi.h unnecessarily.
     >      >
     >      > Without that patch, GCC actually builds soft-float code, even though
     >      > you may have passed the --with-float=hard flag.  What bits of that
     >      > patch do you think are not necessary?
     >      
     >      All of it seems to be unnecessary, by experiment.  I've used the
     >      resulting GCC to compile the following test program:
     >      
     >      'foo' accepts the double arguments via registers and passes a double to
     >      sinh via registers.  I also checked a variant that simply returned a*b,
     >      and it was clearly returning the result via register as well.
     >      
     >      I think it's quite clear that this is using the hard-float ABI, no?
     >
     > My results showed that simple binaries like that compiled (and ran)
     > ok.  The problems arose when linking with bigger projects.  I don't
     > recall the details.  Have you tried building libc?
     
     Yes, of course.  I looked further into this, and discovered that the
     reason it all works is that the main 'gcc' driver arranges to pass
     "-mfloat-abi=hard" (and several others) to 'cc1' and 'as'.
     
Ok.  Right now, I don't remember exactly at what point I discovered the linux-eabi.h
changes were necessary, but they were indeed necessary - I didn't do it for fun!
I expect you will find out in due course.

J'

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