[llvm] [VPlan] Move addExplicitVectorLength to tryToBuildVPlanWithVPRecipes (PR #166164)

[Luke Lau via llvm-commits]

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@@ -42,10 +42,8 @@ define i32 @reduction(ptr %a, i64 %n, i32 %start) {
 ; IF-EVL-OUTLOOP-NEXT:    WIDEN-REDUCTION-PHI ir<[[RDX_PHI:%.+]]> = phi vp<[[RDX_START]]>, vp<[[RDX_SELECT:%.+]]>
 ; IF-EVL-OUTLOOP-NEXT:    EMIT-SCALAR vp<[[AVL:%.+]]> = phi [ ir<%n>, vector.ph ], [ vp<[[AVL_NEXT:%.+]]>, vector.body ] 
 ; IF-EVL-OUTLOOP-NEXT:    EMIT-SCALAR vp<[[EVL:%.+]]> = EXPLICIT-VECTOR-LENGTH vp<[[AVL]]>
-; IF-EVL-OUTLOOP-NEXT:    vp<[[ST:%[0-9]+]]> = SCALAR-STEPS vp<[[EVL_PHI]]>, ir<1>, vp<[[EVL]]>
-; IF-EVL-OUTLOOP-NEXT:    CLONE ir<[[GEP1:%.+]]> = getelementptr inbounds ir<%a>, vp<[[ST]]>
-; IF-EVL-OUTLOOP-NEXT:    vp<[[PTR1:%[0-9]+]]> = vector-pointer ir<[[GEP1]]>
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lukel97 wrote:

We did remove the redundant vector pointers before, just during the second call to optimise which is after the initial VPlan is debug printed. 

This change also means we do it before the cost model now IIUC so it's not NFC

https://github.com/llvm/llvm-project/pull/166164