[llvm] [VPlan] Introduce VPInstruction::InsertLastLane for start value of VPFirstOrderRecurrencePHIRecipe. (PR #171590)

[Mel Chen via llvm-commits]

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@@ -10,7 +10,8 @@ define i8 @recurrence_phi_with_same_incoming_values_after_simplifications(i8 %fo
 ; CHECK:       [[VECTOR_PH]]:
 ; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i8> poison, i8 [[FOR_START]], i64 0
 ; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i8> [[BROADCAST_SPLATINSERT]], <4 x i8> poison, <4 x i32> zeroinitializer
-; CHECK-NEXT:    [[TMP0:%.*]] = shufflevector <4 x i8> [[BROADCAST_SPLAT]], <4 x i8> [[BROADCAST_SPLAT]], <4 x i32> <i32 3, i32 4, i32 5, i32 6>
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Mel-Chen wrote:

By the way, we need a simplification: FOR splice(op, op) --> op.

https://github.com/llvm/llvm-project/pull/171590