[X86] combineINSERT_SUBVECTOR - peek through bitcasts to find a concatenation of subvector shuffles (#131331)

Extend existing concat(shuffle(),shuffle(),..) shuffle combining to handle mixed bitcasts such as concat(shuffle(),bitcast(shuffle()),...)

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -58818,7 +58818,7 @@ static SDValue combineINSERT_SUBVECTOR(SDNode *N, SelectionDAG &DAG,
 
     // Attempt to recursively combine to a shuffle.
     if (all_of(SubVectorOps, [](SDValue SubOp) {
-          return isTargetShuffle(SubOp.getOpcode());
+          return isTargetShuffle(peekThroughBitcasts(SubOp).getOpcode());
         })) {
       SDValue Op(N, 0);
       if (SDValue Res = combineX86ShufflesRecursively(Op, DAG, Subtarget))

llvm/test/CodeGen/X86/vector-interleaved-store-i16-stride-5.ll

@@ -168,8 +168,7 @@ define <64 x i8> @shuffle_v64i8_63_62_61_60_59_58_57_56_55_54_53_52_51_50_49_48_
 ; AVX512F-NEXT:    vpshufb %ymm1, %ymm0, %ymm2
 ; AVX512F-NEXT:    vextracti64x4 $1, %zmm0, %ymm0
 ; AVX512F-NEXT:    vpshufb %ymm1, %ymm0, %ymm0
-; AVX512F-NEXT:    vinserti64x4 $1, %ymm2, %zmm0, %zmm0
-; AVX512F-NEXT:    vpermq {{.*#+}} zmm0 = zmm0[2,3,0,1,6,7,4,5]
+; AVX512F-NEXT:    vshufi64x2 {{.*#+}} zmm0 = zmm0[2,3,0,1],zmm2[2,3,0,1]
 ; AVX512F-NEXT:    retq
 ;
 ; AVX512BW-LABEL: shuffle_v64i8_63_62_61_60_59_58_57_56_55_54_53_52_51_50_49_48_47_46_45_44_43_42_41_40_39_38_37_36_35_34_33_32_31_30_29_28_27_26_25_24_23_22_21_20_19_18_17_16_15_14_13_12_11_10_09_08_07_06_05_04_03_02_01_00:
@@ -185,8 +184,7 @@ define <64 x i8> @shuffle_v64i8_63_62_61_60_59_58_57_56_55_54_53_52_51_50_49_48_
 ; AVX512DQ-NEXT:    vpshufb %ymm1, %ymm0, %ymm2
 ; AVX512DQ-NEXT:    vextracti64x4 $1, %zmm0, %ymm0
 ; AVX512DQ-NEXT:    vpshufb %ymm1, %ymm0, %ymm0
-; AVX512DQ-NEXT:    vinserti64x4 $1, %ymm2, %zmm0, %zmm0
-; AVX512DQ-NEXT:    vpermq {{.*#+}} zmm0 = zmm0[2,3,0,1,6,7,4,5]
+; AVX512DQ-NEXT:    vshufi64x2 {{.*#+}} zmm0 = zmm0[2,3,0,1],zmm2[2,3,0,1]
 ; AVX512DQ-NEXT:    retq
 ;
 ; AVX512VBMI-LABEL: shuffle_v64i8_63_62_61_60_59_58_57_56_55_54_53_52_51_50_49_48_47_46_45_44_43_42_41_40_39_38_37_36_35_34_33_32_31_30_29_28_27_26_25_24_23_22_21_20_19_18_17_16_15_14_13_12_11_10_09_08_07_06_05_04_03_02_01_00: