[PATCH] D59710: [SLP] remove lower limit for forming reduction patterns

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added inline comments.


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Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:7135
+      for (auto *V : LastInst->operand_values()) {
+        Changed |= vectorizeRootInstruction(nullptr, V, BB, R, TTI, 2);
+      }
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The only problem with this solution that it may increase the compiler time. It would be good to limit it strictly only to try to vectorize 2-vals reductions. Thoughts?


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Comment at: llvm/test/Transforms/SLPVectorizer/X86/hadd.ll:93
+; SLM-NEXT:    [[R01:%.*]] = shufflevector <2 x i64> [[BIN_RDX2]], <2 x i64> [[BIN_RDX]], <2 x i32> <i32 0, i32 2>
 ; SLM-NEXT:    ret <2 x i64> [[R01]]
 ;
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RKSimon wrote:
> SLM has really poor v2i64 add costs - so I'm surprised this happened - we may need SLM special handling in getArithmeticReductionCost?
I think it is the problem of the cost model, maybe SLM cost model is not aware of very expensive 2i64 add cost?


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  https://reviews.llvm.org/D59710/new/

https://reviews.llvm.org/D59710