RFR(S):8216050:X86: Fix for Superword optimization fails with assert(0 <= i && i < _len) failed: illegal index
Deshpande, Vivek R
vivek.r.deshpande at intel.com
Tue Jan 15 00:17:05 UTC 2019
Thanks for looking at the patch.
The MulAddS2I node gets packed in follow_use_defs() with this approach in which we just perform swaps in follow_def_uses and return false.
This way MulAddS2I nodes gets the right alignment of multiple of 4 from its outs.
If we return true after the swaps in follow_def_uses(), it gets alignment as multiple of 2(from LoadS) for packing, instead of multiple of 4.
From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com]
Sent: Monday, January 14, 2019 2:37 PM
To: Deshpande, Vivek R <vivek.r.deshpande at intel.com>; Tobias Hartmann <tobias.hartmann at oracle.com>; hotspot-compiler-dev at openjdk.java.net compiler <hotspot-compiler-dev at openjdk.java.net>
Cc: Raj, Guru <guru.raj at intel.com>
Subject: Re: RFR(S):8216050:X86: Fix for Superword optimization fails with assert(0 <= i && i < _len) failed: illegal index
I do not understand changes in superword.cpp.
muladds2i will never be packed in follow_def_uses() since you return 'false' for muladds2i in all cases when u1 != u2 (even when i1 == i2). Is it intentional?
On 1/11/19 11:38 AM, Deshpande, Vivek R wrote:
> Hi Tobias
> Thanks for reviewing the patch.
> I have made the changes according to your suggestion.
> In this webrev:
> I have fix for the crash reported in the 8216050.
> The lower cost is needed for generation of vpdpwssd instruction, by combining AddVI and MulAddVS2VI.
> For other instructions pmaddwd and vpmaddwd, they get generated on platforms upto skylake with default cost.
> I have updated the bug also with the link to webrev.
> I have created a different bug JDK-8216580 for
> 3) Fix generation of vector code by allowing adjacent LoadS nodes to be isomorphic when they have different control RangeCheck nodes
> for a[i] and a[i+1] accesses in same MulAddS2I node
> Thank you.
> -----Original Message-----
> From: Tobias Hartmann [mailto:tobias.hartmann at oracle.com]
> Sent: Friday, January 11, 2019 4:49 AM
> To: Deshpande, Vivek R <vivek.r.deshpande at intel.com>;
> hotspot-compiler-dev at openjdk.java.net compiler
> <hotspot-compiler-dev at openjdk.java.net>
> Cc: Vladimir Kozlov <vladimir.kozlov at oracle.com>; Viswanathan, Sandhya
> <sandhya.viswanathan at intel.com>; Raj, Guru <guru.raj at intel.com>
> Subject: Re: RFR(S):8216050:X86: Fix for Superword optimization fails
> with assert(0 <= i && i < _len) failed: illegal index
> Hi Vivek,
> On 11.01.19 07:58, Deshpande, Vivek R wrote:
>> 1) Fix for the crash by matching the operand by swapping to right positions.
> Looks good but the change to loopopts.cpp:530 screwed up the indentation around the ifs, please fix.
>> 2) Cost based generation of vpdpwssd instruction.
> Other instructions added by JDK-8214751 still miss a cost definition, for example:
>> 3) Fix generation of vector code by allowing adjacent LoadS nodes to
>> be isomorphic when they have different control RangeCheck nodes
>> for a[i] and a[i+1] accesses in same MulAddS2I node
> This is unrelated to the original bug, right? If so, this should be integrated with a separate RFE.
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