[X86][Costmodel] Load/store i8 Stride=2 VF=2 interleaving costs

[lebedev.ri]

Summary

The only sched models that for cpu's that support avx2
but not avx512 are: haswell, broadwell, skylake, zen1-3

For load we have:
https://godbolt.org/z/caKqjr9hb - for intels Block RThroughput: =2.0; for ryzens, Block RThroughput: <=1.0
So pick cost of 2.

For store we have:
https://godbolt.org/z/6TTn3eKj8 - for intels Block RThroughput: =1.0; for ryzens, Block RThroughput: <=0.5
So pick cost of 1.

I'm directly using the shuffling asm the llc produced,
without any manual fixups that may be needed
to ensure sequential execution.

[RKSimon]

LGTM

llvm/lib/Target/X86/X86TargetTransformInfo.cpp

InstructionCost X86TTIImpl::getInterleavedMemoryOpCostAVX2(
   // TODO: Complete for other data-types and strides.
   // Each combination of Stride, element bit width and VF results in a different
   // sequence; The cost tables are therefore accessed with:
   // Factor (stride) and VectorType=VFxiN.
   // The Cost accounts only for the shuffle sequence;
   // The cost of the loads/stores is accounted for separately.
   //
   static const CostTblEntry AVX2InterleavedLoadTbl[] = {
+      {2, MVT::v2i8, 2},  // (load 4i8 and) deinterleave into 2 x 2i8
+
       {2, MVT::v2i16, 2}, // (load 4i16 and) deinterleave into 2 x 2i16
       {2, MVT::v4i16, 2}, // (load 8i16 and) deinterleave into 2 x 4i16
       {2, MVT::v8i16, 6}, // (load 16i16 and) deinterleave into 2 x 8i16
       {2, MVT::v16i16, 9}, // (load 32i16 and) deinterleave into 2 x 16i16
       {2, MVT::v32i16, 18}, // (load 64i16 and) deinterleave into 2 x 32i16
 
       {2, MVT::v4i64, 6}, // (load 8i64 and) deinterleave into 2 x 4i64
 
static const CostTblEntry AVX2InterleavedLoadTbl[] = {
       {6, MVT::v4i16, 9}, // (load 24i16 and) deinterleave into 6 x 4i16
       {6, MVT::v8i16, 39}, // (load 48i16 and) deinterleave into 6 x 8i16
       {6, MVT::v16i16, 106}, // (load 96i16 and) deinterleave into 6 x 16i16
 
       {8, MVT::v8i32, 40} // (load 64i32 and) deinterleave into 8 x 8i32
   };
 
   static const CostTblEntry AVX2InterleavedStoreTbl[] = {
+      {2, MVT::v2i8, 1}, // interleave 2 x 2i8 into 4i8 (and store)
+
       {2, MVT::v2i16, 1}, // interleave 2 x 2i16 into 4i16 (and store)
       {2, MVT::v4i16, 1}, // interleave 2 x 4i16 into 8i16 (and store)
       {2, MVT::v8i16, 3}, // interleave 2 x 8i16 into 16i16 (and store)
       {2, MVT::v16i16, 4}, // interleave 2 x 16i16 into 32i16 (and store)
       {2, MVT::v32i16, 8}, // interleave 2 x 32i16 into 64i16 (and store)
 
       {2, MVT::v4i64, 6}, // interleave 2 x 4i64 into 8i64 (and store)
 

llvm/test/Analysis/CostModel/X86/interleaved-load-i8-stride-2.ll

 ; AVX1: LV: Found an estimated cost of 1 for VF 1 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX1: LV: Found an estimated cost of 9 for VF 2 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX1: LV: Found an estimated cost of 17 for VF 4 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX1: LV: Found an estimated cost of 33 for VF 8 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX1: LV: Found an estimated cost of 81 for VF 16 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX1: LV: Found an estimated cost of 166 for VF 32 For instruction:   %v0 = load i8, i8* %in0, align 1
 ;
 ; AVX2: LV: Found an estimated cost of 1 for VF 1 For instruction:   %v0 = load i8, i8* %in0, align 1
-; AVX2: LV: Found an estimated cost of 9 for VF 2 For instruction:   %v0 = load i8, i8* %in0, align 1
+; AVX2: LV: Found an estimated cost of 3 for VF 2 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX2: LV: Found an estimated cost of 17 for VF 4 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX2: LV: Found an estimated cost of 33 for VF 8 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX2: LV: Found an estimated cost of 81 for VF 16 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX2: LV: Found an estimated cost of 166 for VF 32 For instruction:   %v0 = load i8, i8* %in0, align 1
 ;
 ; AVX512: LV: Found an estimated cost of 1 for VF 1 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX512: LV: Found an estimated cost of 3 for VF 2 For instruction:   %v0 = load i8, i8* %in0, align 1
 ; AVX512: LV: Found an estimated cost of 3 for VF 4 For instruction:   %v0 = load i8, i8* %in0, align 1

llvm/test/Analysis/CostModel/X86/interleaved-store-i8-stride-2.ll

 ; AVX1: LV: Found an estimated cost of 1 for VF 1 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX1: LV: Found an estimated cost of 9 for VF 2 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX1: LV: Found an estimated cost of 17 for VF 4 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX1: LV: Found an estimated cost of 33 for VF 8 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX1: LV: Found an estimated cost of 67 for VF 16 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX1: LV: Found an estimated cost of 166 for VF 32 For instruction:   store i8 %v1, i8* %out1, align 1
 
 ; AVX2: LV: Found an estimated cost of 1 for VF 1 For instruction:   store i8 %v1, i8* %out1, align 1
-; AVX2: LV: Found an estimated cost of 9 for VF 2 For instruction:   store i8 %v1, i8* %out1, align 1
+; AVX2: LV: Found an estimated cost of 2 for VF 2 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX2: LV: Found an estimated cost of 17 for VF 4 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX2: LV: Found an estimated cost of 33 for VF 8 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX2: LV: Found an estimated cost of 67 for VF 16 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX2: LV: Found an estimated cost of 166 for VF 32 For instruction:   store i8 %v1, i8* %out1, align 1
 ;
 ; AVX512: LV: Found an estimated cost of 1 for VF 1 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX512: LV: Found an estimated cost of 4 for VF 2 For instruction:   store i8 %v1, i8* %out1, align 1
 ; AVX512: LV: Found an estimated cost of 4 for VF 4 For instruction:   store i8 %v1, i8* %out1, align 1