[llvm] [LV] Add initial cost model for VPScalarIVSteps (PR #203347)

[David Sherwood via llvm-commits]

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@@ -424,75 +424,48 @@ define i32 @load_from_pointer_induction(ptr %start, ptr %end) {
 ; CHECK-NEXT:    [[UMAX:%.*]] = call i64 @llvm.umax.i64(i64 [[END1]], i64 [[START2]])
 ; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[UMAX]], 1
 ; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 [[TMP0]], [[START2]]
-; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP1]], 8
+; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP1]], 2
 ; CHECK-NEXT:    br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
 ; CHECK:       [[VECTOR_PH]]:
-; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[TMP1]], 8
+; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[TMP1]], 2
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[TMP1]], [[N_MOD_VF]]
 ; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr i8, ptr [[START]], i64 [[N_VEC]]
 ; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
 ; CHECK:       [[VECTOR_BODY]]:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi <4 x i32> [ zeroinitializer, %[[VECTOR_PH]] ], [ [[TMP28:%.*]], %[[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[VEC_PHI3:%.*]] = phi <4 x i32> [ zeroinitializer, %[[VECTOR_PH]] ], [ [[TMP29:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi i32 [ 0, %[[VECTOR_PH]] ], [ [[TMP8:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_PHI3:%.*]] = phi i32 [ 0, %[[VECTOR_PH]] ], [ [[TMP9:%.*]], %[[VECTOR_BODY]] ]
 ; CHECK-NEXT:    [[TMP3:%.*]] = add i64 [[INDEX]], 1
-; CHECK-NEXT:    [[TMP4:%.*]] = add i64 [[INDEX]], 2
-; CHECK-NEXT:    [[TMP5:%.*]] = add i64 [[INDEX]], 3
-; CHECK-NEXT:    [[TMP6:%.*]] = add i64 [[INDEX]], 4
-; CHECK-NEXT:    [[TMP7:%.*]] = add i64 [[INDEX]], 5
-; CHECK-NEXT:    [[TMP8:%.*]] = add i64 [[INDEX]], 6
-; CHECK-NEXT:    [[TMP9:%.*]] = add i64 [[INDEX]], 7
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david-arm wrote:

Yeah, that's a good point. Essentially this may just be a cost of a single add. I'll update the patch.

https://github.com/llvm/llvm-project/pull/203347