[LLVMdev] bx instruction getting generated in arm assembly for O1

[Mayur Pandey]

Hi Tim,

Thanks for the response. Even I thought this might be the result of tail
call optimisation in O1, but with clang-3.4.2 this behaviour is not seen in
O1, so wanted to know which change triggered this behaviour in O1 in
clang-3.5.

Thanks,
Mayur

On Mon, Nov 24, 2014 at 10:55 PM, Tim Northover <tnorthover at apple.com>
wrote:

> Hi Mayur,
>
> > On 24 Nov 2014, at 07:00, MAYUR PANDEY <mayur.p at samsung.com> wrote:
> > In the assembly generated with O0, we are getting the "blx" instruction
> whereas with O1 we get "bx" (in 3.4.2 we used to get "blx" for both O0 and
> O1).
> >
> > Is this because of this patch:  [llvm] r214959 - ARM: do not generate
> BLX instructions on Cortex-M CPUs
>
> Isn't this just the usual tail call optimisations kicking in at O1? Or is
> there some problem with this behaviour that I'm missing (both variants seem
> to be supported on v5t).
>
> Cheers.
>
> Tim.
>
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-- 
Thanx & Regards
*Mayur Pandey *
Lead Engineer
Samsung R&D Institute India
Bangalore
+91-9742959541
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