[llvm] [VPlan] Generalize vputils::getStrideExpr for known-sign (PR #219152)

[Florian Hahn via llvm-commits]

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@@ -20,12 +20,12 @@ define void @negative_stride_nuw(ptr noalias %src, ptr noalias %dst) {
 ; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
 ; CHECK:       [[VECTOR_BODY]]:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[TMP8:%.*]] = mul i64 [[INDEX]], -8
+; CHECK-NEXT:    [[TMP8:%.*]] = shl i64 [[INDEX]], 3
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fhahn wrote:

It looks like most (all?) test changes are incorrectly flipping from negative to positive stride

https://github.com/llvm/llvm-project/pull/219152