[PATCH] D62890: [DAGCombiner] Improve tryStoreMergeOfExtracts by using double sized vector type before type legalized

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: llvm/test/CodeGen/PowerPC/extract-and-store.ll:733
+; CHECK-NEXT:    xxswapd vs0, vs34
+; CHECK-NEXT:    stfdx f0, 0, r5
 ; CHECK-NEXT:    blr
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tingwang wrote:
> RKSimon wrote:
> > is this really an issue with the store merging or the ppc shuffle combines have gotten messed up?
> Had a quick check, this is the case PPC::LowerVECTOR_SHUFFLE does not have efficient solution, so it turned into VPERM as last resort.
> 
> Probably the cost function should avoid this kind of situation.
I'd be nervous about a cost function as that is likely to be very difficult to keep balanced. I'd probably recommend just overriding canMergeStoresTo or isMultiStoresCheaperThanBitsMerge for PPC


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  https://reviews.llvm.org/D62890/new/

https://reviews.llvm.org/D62890