[llvm] [X86] Use GFNI for vXi8 shifts/rotates (PR #89115)

[Simon Pilgrim via llvm-commits]

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@@ -98,34 +72,25 @@ define <16 x i8> @splatconstant_ashr_v16i8(<16 x i8> %a) nounwind {
 define <32 x i8> @splatconstant_shl_v32i8(<32 x i8> %a) nounwind {
 ; GFNISSE-LABEL: splatconstant_shl_v32i8:
 ; GFNISSE:       # %bb.0:
-; GFNISSE-NEXT:    psllw $6, %xmm0
-; GFNISSE-NEXT:    movdqa {{.*#+}} xmm2 = [192,192,192,192,192,192,192,192,192,192,192,192,192,192,192,192]
-; GFNISSE-NEXT:    pand %xmm2, %xmm0
-; GFNISSE-NEXT:    psllw $6, %xmm1
-; GFNISSE-NEXT:    pand %xmm2, %xmm1
+; GFNISSE-NEXT:    pmovsxwq {{.*#+}} xmm2 = [258,258]
+; GFNISSE-NEXT:    gf2p8affineqb $0, %xmm2, %xmm0
+; GFNISSE-NEXT:    gf2p8affineqb $0, %xmm2, %xmm1
 ; GFNISSE-NEXT:    retq
 ;
 ; GFNIAVX1-LABEL: splatconstant_shl_v32i8:
 ; GFNIAVX1:       # %bb.0:
-; GFNIAVX1-NEXT:    vextractf128 $1, %ymm0, %xmm1
-; GFNIAVX1-NEXT:    vpsllw $6, %xmm1, %xmm1
-; GFNIAVX1-NEXT:    vbroadcastss {{.*#+}} xmm2 = [192,192,192,192,192,192,192,192,192,192,192,192,192,192,192,192]
-; GFNIAVX1-NEXT:    vpand %xmm2, %xmm1, %xmm1
-; GFNIAVX1-NEXT:    vpsllw $6, %xmm0, %xmm0
-; GFNIAVX1-NEXT:    vpand %xmm2, %xmm0, %xmm0
-; GFNIAVX1-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; GFNIAVX1-NEXT:    vgf2p8affineqb $0, {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %ymm0, %ymm0
 ; GFNIAVX1-NEXT:    retq
 ;
 ; GFNIAVX2-LABEL: splatconstant_shl_v32i8:
 ; GFNIAVX2:       # %bb.0:
-; GFNIAVX2-NEXT:    vpsllw $6, %ymm0, %ymm0
-; GFNIAVX2-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %ymm0, %ymm0
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RKSimon wrote:

I'll look at the funnel shift codegen.

Regarding the broadcast - lowerBuildVectorAsBroadcast will only attempt to match i32/i64 constant broadcasts - nothing smaller as Haswell struggled with i8/i16 perf - we went from a v16i16 to a v4i64 constant broadcast. I really want to stop lowering to broadcasting constants in DAG entirely and allow X86FixupVectorConstants to handle it all, but there's still a lot of minor issues to address - #73509 started the work on AVX512 but it keeps getting dropped down my TODO list :( 

https://github.com/llvm/llvm-project/pull/89115