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Re: [PATCH][AArch64][doc] Clarify -msve-vector-bits=128 behaviour


Ramana Radhakrishnan <ramana.gcc@googlemail.com> writes:
> On Thu, Dec 13, 2018 at 10:15 AM Richard Sandiford
> <richard.sandiford@arm.com> wrote:
>>
>> Thanks for doing this.
>>
>> "Kyrill Tkachov" <kyrylo.tkachov@foss.arm.com> writes:
>> > @@ -15716,16 +15716,19 @@ an effect when SVE is enabled.
>> >
>> >  GCC supports two forms of SVE code generation: ``vector-length
>> >  agnostic'' output that works with any size of vector register and
>> > -``vector-length specific'' output that only works when the vector
>> > -registers are a particular size.  Replacing @var{bits} with
>> > -@samp{scalable} selects vector-length agnostic output while
>> > -replacing it with a number selects vector-length specific output.
>> > -The possible lengths in the latter case are: 128, 256, 512, 1024
>> > -and 2048.  @samp{scalable} is the default.
>> > -
>> > -At present, @samp{-msve-vector-bits=128} produces the same output
>> > -as @samp{-msve-vector-bits=scalable}.
>> > -
>> > +``vector-length specific'' output that allows GCC to make assumptions
>> > +about the vector length when it is useful for optimization reasons.
>> > +The possible values of @samp{bits} are: @samp{scalable}, @samp{128},
>> > +@samp{256}, @samp{512}, @samp{1024} and @samp{2048}.
>> > +Specifying @samp{scalable} selects vector-length agnostic
>> > +output.  At present @samp{-msve-vector-bits=128} also generates vector-length
>> > +agnostic output.  All other values generate vector-length specific code.
>> > +The behavior of these values may change in future releases and no value except
>> > +@samp{scalable} should be relied on for producing code that is portable across
>> > +different hardware SVE vector lengths.
>> > +
>> > +The default is @samp{-msve-vector-bits=scalable} which produces
>> > +vector-length agnostic code.
>>
>> Think we should have a comma before "which" in the last sentence.
>> OK with that change.
>
> And backport to GCC-8 ?

Yeah, OK for the backport too.


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