[llvm] [LV] Improve cost model for some replicating recipes (PR #192056)

[Florian Hahn via llvm-commits]

================
@@ -380,22 +380,70 @@ exit:
 define void @sdiv_power_of_2_divisor_in_replicate_region(i32 %x, ptr %dst, i64 %n) {
 ; CHECK-LABEL: define void @sdiv_power_of_2_divisor_in_replicate_region(
 ; CHECK-SAME: i32 [[X:%.*]], ptr [[DST:%.*]], i64 [[N:%.*]]) {
-; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:  [[ENTRY:.*:]]
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp sgt i64 [[N]], 0
 ; CHECK-NEXT:    [[C_2:%.*]] = icmp slt i64 [[N]], 9
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[C_1]])
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[C_2]])
 ; CHECK-NEXT:    br label %[[LOOP:.*]]
 ; CHECK:       [[LOOP]]:
-; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP]] ]
+; CHECK-NEXT:    [[N_RND_UP:%.*]] = add i64 [[N]], 3
+; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[N_RND_UP]], 4
+; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[N_RND_UP]], [[N_MOD_VF]]
+; CHECK-NEXT:    [[TRIP_COUNT_MINUS_1:%.*]] = sub i64 [[N]], 1
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i64> poison, i64 [[TRIP_COUNT_MINUS_1]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i64> [[BROADCAST_SPLATINSERT]], <4 x i64> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
+; CHECK:       [[VECTOR_BODY]]:
----------------
fhahn wrote:

> It's possibly not profitable, but then I don't think that's because of this PR.

Yep agreed that this may expose a different underlying issue in some cases. But it would be good to at least have some tests that show positive impact and check it doesn't cause any regressions in practice. 

https://github.com/llvm/llvm-project/pull/192056