[llvm] AMDGPU/GlobalISel: RegBankLegalize rules for s_bitreplicate (PR #189138)

[Petar Avramovic via llvm-commits]

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@@ -1451,6 +1451,10 @@ RegBankLegalizeRules::RegBankLegalizeRules(const GCNSubtarget &_ST,
 
   using namespace Intrinsic;
 
+  addRulesForIOpcs({amdgcn_s_bitreplicate}, Standard)
+      .Uni(S64, {{Sgpr64}, {IntrId, Sgpr32}})
+      .Div(S64, {{Sgpr64ToVgprDst}, {IntrId, SgprB32_ReadFirstLane}});
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petar-avramovic wrote:

This can be waterfall I think, here it is just bitreplaces value from first active lane and splat to dst, but with waterfall loop it would do it per lane and copy to lane in dst

https://github.com/llvm/llvm-project/pull/189138