[LLVMdev] NEON intrinsics preventing redundant load optimization?

[Simon Taylor]

> On 5 Jan 2015, at 13:08, Renato Golin <renato.golin at linaro.org> wrote:
> 
> On 5 January 2015 at 12:13, James Molloy <james at jamesmolloy.co.uk> wrote:
>> For this reason Renato I don't think we should advise people to work around
>> the API, as who knows what problems that will cause later.
> 
> I stand corrected (twice). But we changed the subject a bit, so things
> got different midway through.
> 
> There were only two codes: full C, with pointers, vectorized some
> times; and full NEON, with extra loads. The mix between the two came
> later, as a quick fix. My comment to that, I agree, was misplaced, and
> both you and Tim are correct is asking for it not to be used as a
> final solution. But as an interim solution, with the care around
> alignment, endian and all, it is "fine”.

After a bit more testing applying the pointer dereferencing workaround in my real code (which has some layers of templates and inline functions) I’ve decided against using it in practice.

GCC produced incorrect code unless -fno-strict-aliasing was specified. It’s probably entirely entitled to do that, so it just seems too flaky to recommend in any case.

Simon