[Bug rtl-optimization/65067] regression on accessing volatile bit field

[tony.liu at arm dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65067

--- Comment #9 from Tony Liu <tony.liu at arm dot com> ---
(In reply to Bernd Edlinger from comment #8)
> Created attachment 34955 [details]
> Proposed Fix
> 
> Well, I noticed that the first version of this patch caused
> a small but measurable decrease of code quality on x86_64,
> so I moved the patch to the if (strict_volatile_bitfield_p block,
> and used some code transformations to simplify the resulting code
> a bit.
> 
> I will post this new version for review, after a full boot-strap
> and successful regression-test on my ARM target.

I've tested for target Cortex-M3, no regression.