XCore target: disable vectorization

[Eric Christopher]

Aha, thanks. Just wanted to make sure. Also, the bool is weird :)

-eric

On Mon, Sep 9, 2013 at 9:21 AM, Arnold Schwaighofer
<aschwaighofer at apple.com> wrote:
> The api is meant to handle scalar and vector:
>
>   /// \return The number of scalar or vector registers that the target has.
>   /// If 'Vectors' is true, it returns the number of vector registers. If it is
>   /// set to false, it returns the number of scalar registers.
>   virtual unsigned getNumberOfRegisters(bool Vector) const;
>
> We don’t actually use the number of scalar registers anywhere and this number would depend on the (dominant) type (so would the vector number).
>
> I think, we can revisit this when we revisit the unrolling heuristic in the loop vectorizer (I have a radar for this, it is just not my highest priority).
>
>
> On Sep 9, 2013, at 11:05 AM, Eric Christopher <echristo at gmail.com> wrote:
>
>> Drive by comment, should probably be "getNumberOfVectorRegisters" or
>> some sort of query with vector in the name :)
>>
>> -eric
>>
>> On Mon, Sep 9, 2013 at 8:43 AM, Arnold Schwaighofer
>> <aschwaighofer at apple.com> wrote:
>>> Hi Robert,
>>>
>>> I think Nadav meant to add code to the LoopVectorizer and SLPVectorizer that calls "TTI.getNumberOfRegisters(true)” and stops vectorization if it returns 0. Something like:
>>>
>>> --- a/lib/Transforms/Vectorize/LoopVectorize.cpp
>>> +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
>>> @@ -906,6 +906,11 @@ struct LoopVectorize : public LoopPass {
>>>     DT = &getAnalysis<DominatorTree>();
>>>     TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
>>>
>>> +    // If the target claims to have no vector registers don't attempt
>>> +    // vectorization.
>>> +    if (!TTI->getNumberOfRegisters(true))
>>> +      return false;
>>> +
>>>     if (DL == NULL) {
>>>       DEBUG(dbgs() << "LV: Not vectorizing because of missing data layout");
>>>       return false;
>>>
>>>
>>>
>>> diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
>>> index 1f288bc..6ddcc51 100644
>>> --- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
>>> +++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
>>> @@ -1565,6 +1565,11 @@ struct SLPVectorizer : public FunctionPass {
>>>     if (!DL)
>>>       return false;
>>>
>>> +    // If the target claims to have no vector registers don't attempt
>>> +    // vectorization.
>>> +    if (!TTI->getNumberOfRegisters(true))
>>> +      return false;
>>> +
>>>     // Don't vectorize when the attribute NoImplicitFloat is used.
>>>     if (F.hasFnAttribute(Attribute::NoImplicitFloat))
>>>       return false;
>>>
>>> On Sep 9, 2013, at 7:13 AM, Robert Lytton <robert at xmos.com> wrote:
>>>
>>>> Hi Rafael, Nadav,
>>>>
>>>> Thank you for the input but I don't follow where the change needs to be made.
>>>>
>>>> Are you suggesting changes to llvm's  lib/Transforms/IPO/PassManagerBuilder.cpp?
>>>> This approach would  make the '-vectorize-loops' & '-vectorize-slp' flags  only relevant for targets with vector registers?
>>>>
>>>> Or in clang/lib/Driver/Tools.cpp?
>>>>
>>>> In either case, I can't see how to get hold of the TargetTransformInfo cleanly.
>>>>
>>>> Robert
>>>>
>>>> ________________________________________
>>>> From: Rafael Espíndola [rafael.espindola at gmail.com]
>>>> Sent: 06 September 2013 18:43
>>>> To: Nadav Rotem
>>>> Cc: Robert Lytton; cfe-commits at cs.uiuc.edu; Arnold Schwaighofer
>>>> Subject: Re: XCore target: disable vectorization
>>>>
>>>>> unsigned TargetVectorRegisters = TTI.getNumberOfRegisters(true);
>>>>
>>>> And not vectorize if the target says 0? I like that idea.
>>>>
>>>> Cheers,
>>>> Rafael
>>>
>>>
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>