[PATCH] D36562: [Bitfield] Make the bitfield a separate location if it has width of legal integer type and its bit offset is naturally aligned for the type

Sun Aug 25 22:40:05 PDT 2019

wmi added a comment.

In D36562#1642403 <https://reviews.llvm.org/D36562#1642403>, @chill wrote:

> In D36562#1641930 <https://reviews.llvm.org/D36562#1641930>, @wmi wrote:
>
> > In D36562#1639441 <https://reviews.llvm.org/D36562#1639441>, @chill wrote:
> >
> > > Shouldn't we disable `OPT_ffine_grained_bitfield_accesses` only if TSAN is active?
> >
> >
> > I don't remember why it is disabled for all sanitizer modes. Seems you are right that the disabling the option is only necessary for TSAN. Do you have actual needs for the option to be functioning on other sanitizer modes?
>
>
> Well, yes and no. We have the option enabled by default and it causes a warning when we use it together with `-fsanitize=memtag` (we aren't really concerned with other sanitizers). That warning broke a few builds (e.g. CMake doing tests and not wanting to see *any* diagnostics. We can work around that in a number of ways, e.g. we can leave the default off for AArch64.
>
> I'd prefer though to have an upstream solution, if that's considered beneficial for all LLVM users and this one seems like such a case: let anyone use the option with sanitizers, unless it's known that some sanitizers'utility is affected negatively (as with TSAN).

Thanks for providing the background in detail. I sent out a patch for it: https://reviews.llvm.org/D66726

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https://reviews.llvm.org/D36562