llvm dev - Jan 2016 - error of using GATHER intrinsic

Hi all,

I am using gather intrinsic to load a value from the same address twice at
the same time. Basically, I used my own pass to changed the following
bitcode:

%a = getelementptr inbounds [100 x double], [100 x double]* %A, i32, 0, i64
0
%1 = load double, double* a, align

to:

%a = getelementptr inbounds [100 x double], [100 x double]* %A, i32, 0, i64
0
%splat.a = insertelement <2 x double*> undef, double* %a, i32 0
%brcst.a = shufflevector <2 x double*> % splat.a, <2 x double*>
undef, <2 x
i32> zeroinitializer
%gep.addr = getelementptr <2 x double*> % brcst.a, <2 x i64>
zeroinitializer
%1_gather = call <2 x double> @llvm.masked.gather.v8f64(<2 x
double*>
%gep.addr, i32 8, <2 x i1> <i1 true, i1, true>, <2 x double>
undef)

I could load my pass successfully with opt, but I got the following errors
when I either run the new bitcode using lli or generate the assembly using
llc:

PromoteIntegerOperand Op #2: 0x41bf3a8: v2f64,ch = masked_gather 0x415ec40,
0x41bf030, 0x41bf280, 0x41bbb30, 0x41becb8<LD16[%a]> [ORD=8] [ID=0]

Do not know how to promote this operator's operand!

Any idea about this error? Or could anyone give me an example how to use
the gather intrinsic if there is something wrong with the way I am using it?

Best,
Zhi
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Hi Zhi,

On 18 January 2016 at 11:28, zhi chen via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Any idea about this error? Or could anyone give me an example how to use
the
> gather intrinsic if there is something wrong with the way I am using it?
Modulo obvious typos, the snippets look like they ought to work (on
trunk at least). Do you have an actual .ll or .bc and llc invocation
that fails?

Cheers.

Tim.

> On Jan 20, 2016, at 12:59 PM, Tim Northover via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi Zhi,
> 
> On 18 January 2016 at 11:28, zhi chen via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> Any idea about this error? Or could anyone give me an example how to
use the
>> gather intrinsic if there is something wrong with the way I am using
it?
> 
> Modulo obvious typos, the snippets look like they ought to work (on
> trunk at least). Do you have an actual .ll or .bc and llc invocation
> that fails?
Only typo that caught my eye is ‘llvm.masked.gather.v8f64’ which should have v2
instead of v8 to match the <2 x double>

Could that be the problem?

Cheers,
Pete
> 
> Cheers.
> 
> Tim.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Hi Tim,

Thanks for your response. It works now if I use llc -mcpu=skylake. But it
still fails if I use -mcpu=core-avx2. It seems that avx2 supports
gather/scatter, but I am not sure why it doesn't work.

Best,
Zhi

On Wed, Jan 20, 2016 at 12:59 PM, Tim Northover <t.p.northover at
gmail.com>
wrote:
> Hi Zhi,
>
> On 18 January 2016 at 11:28, zhi chen via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Any idea about this error? Or could anyone give me an example how to
use
> the
> > gather intrinsic if there is something wrong with the way I am using
it?
>
> Modulo obvious typos, the snippets look like they ought to work (on
> trunk at least). Do you have an actual .ll or .bc and llc invocation
> that fails?
>
> Cheers.
>
> Tim.
>
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