[llvm] [X86] getFauxShuffleMask - insert_subvector - skip undemanded subvectors (PR #129042)

[Phoebe Wang via llvm-commits]

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@@ -3004,76 +3004,81 @@ define void @vec384_i16_widen_to_i48_factor3_broadcast_to_v8i48_factor8(ptr %in.
 ;
 ; AVX2-SLOW-LABEL: vec384_i16_widen_to_i48_factor3_broadcast_to_v8i48_factor8:
 ; AVX2-SLOW:       # %bb.0:
-; AVX2-SLOW-NEXT:    vpbroadcastw (%rdi), %xmm0
+; AVX2-SLOW-NEXT:    vpbroadcastw (%rdi), %ymm0
 ; AVX2-SLOW-NEXT:    vpxor %xmm1, %xmm1, %xmm1
-; AVX2-SLOW-NEXT:    vpblendw {{.*#+}} xmm1 = xmm1[0,1],xmm0[2],xmm1[3,4],xmm0[5],xmm1[6,7]
+; AVX2-SLOW-NEXT:    vpblendw {{.*#+}} ymm1 = ymm1[0],ymm0[1],ymm1[2,3],ymm0[4],ymm1[5,6],ymm0[7],ymm1[8],ymm0[9],ymm1[10,11],ymm0[12],ymm1[13,14],ymm0[15]
 ; AVX2-SLOW-NEXT:    vpblendw {{.*#+}} xmm2 = xmm0[0],mem[1,2],xmm0[3],mem[4,5],xmm0[6],mem[7]
-; AVX2-SLOW-NEXT:    vinserti128 $1, %xmm0, %ymm2, %ymm0
-; AVX2-SLOW-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %ymm0, %ymm0
-; AVX2-SLOW-NEXT:    vpaddb (%rsi), %ymm0, %ymm0
-; AVX2-SLOW-NEXT:    vpaddb 32(%rsi), %ymm1, %ymm1
-; AVX2-SLOW-NEXT:    vmovdqa %ymm1, 32(%rdx)
-; AVX2-SLOW-NEXT:    vmovdqa %ymm0, (%rdx)
+; AVX2-SLOW-NEXT:    vpblendd {{.*#+}} ymm1 = ymm2[0,1,2,3],ymm1[4,5,6,7]
+; AVX2-SLOW-NEXT:    vpxor %xmm2, %xmm2, %xmm2
+; AVX2-SLOW-NEXT:    vpblendw {{.*#+}} xmm0 = xmm2[0,1],xmm0[2],xmm2[3,4],xmm0[5],xmm2[6,7]
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phoebewang wrote:

There are more similar patterns.

https://github.com/llvm/llvm-project/pull/129042