[X86][Costmodel] `trunc v16i8 to v8i1` can appear after legalization, cost is same as for `trunc v8i8 to v8i1`

[lebedev.ri]

Summary

Note that there are many other missing costs, i'm *only* adding the ones that are queried
from getReplicationShuffleCost() for the existing (quite exhaustive) test coverage.

[RKSimon]

LGTM

[lebedev.ri]

In D114070#3138296, @RKSimon wrote:

LGTM

Thank you for the reviews!

Are there any thoughts on the D113915+D114071?
After that i guess i will need look into AVX512DQ's {k}->{i32,i64} (all costs are missing?).

llvm/lib/Target/X86/X86TargetTransformInfo.cpp

static const TypeConversionCostTblEntry AVX512BWConversionTbl[] {
     { ISD::TRUNCATE,    MVT::v16i8,  MVT::v16i16, 2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v2i1,   MVT::v2i8,   2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v2i1,   MVT::v2i16,  2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v2i8,   MVT::v2i16,  2 }, // vpmovwb
     { ISD::TRUNCATE,    MVT::v4i1,   MVT::v4i8,   2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v4i1,   MVT::v4i16,  2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v4i8,   MVT::v4i16,  2 }, // vpmovwb
     { ISD::TRUNCATE,    MVT::v8i1,   MVT::v8i8,   2 }, // widen to zmm
+    { ISD::TRUNCATE,    MVT::v8i1,   MVT::v16i8,  2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v8i1,   MVT::v8i16,  2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v8i8,   MVT::v8i16,  2 }, // vpmovwb
     { ISD::TRUNCATE,    MVT::v16i1,  MVT::v16i8,  2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v16i1,  MVT::v16i16, 2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v32i1,  MVT::v32i8,  2 }, // widen to zmm
     { ISD::TRUNCATE,    MVT::v32i1,  MVT::v32i16, 2 },
     { ISD::TRUNCATE,    MVT::v64i1,  MVT::v32i16, 2 },
     { ISD::TRUNCATE,    MVT::v64i1,  MVT::v64i8,  2 },

llvm/test/Analysis/CostModel/X86/trunc.ll

 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %V640i16 = trunc <640 x i16> undef to <640 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %V768i16 = trunc <768 x i16> undef to <768 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %V896i16 = trunc <896 x i16> undef to <896 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %V1024i16 = trunc <1024 x i16> undef to <1024 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %i8 = trunc i8 undef to i1
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V2i8 = trunc <2 x i8> undef to <2 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V3i8 = trunc <3 x i8> undef to <3 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V4i8 = trunc <4 x i8> undef to <4 x i1>
-; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %V5i8 = trunc <5 x i8> undef to <5 x i1>
-; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %V6i8 = trunc <6 x i8> undef to <6 x i1>
-; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 14 for instruction: %V7i8 = trunc <7 x i8> undef to <7 x i1>
+; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V5i8 = trunc <5 x i8> undef to <5 x i1>
+; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V6i8 = trunc <6 x i8> undef to <6 x i1>
+; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V7i8 = trunc <7 x i8> undef to <7 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V8i8 = trunc <8 x i8> undef to <8 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V10i8 = trunc <10 x i8> undef to <10 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V12i8 = trunc <12 x i8> undef to <12 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V14i8 = trunc <14 x i8> undef to <14 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V16i8 = trunc <16 x i8> undef to <16 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V20i8 = trunc <20 x i8> undef to <20 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V24i8 = trunc <24 x i8> undef to <24 x i1>
 ; AVX512BW-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V28i8 = trunc <28 x i8> undef to <28 x i1>