[llvm] [AArch64][CostModel] Improve cost estimate of scalarizing a vector di… (PR #118055)

[David Sherwood via llvm-commits]

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@@ -7,21 +7,21 @@ define i32 @sdiv() {
 ; CHECK-LABEL: 'sdiv'
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %I128 = sdiv i128 undef, undef
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %I64 = sdiv i64 undef, undef
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 28 for instruction: %V2i64 = sdiv <2 x i64> undef, undef
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david-arm wrote:

It feels like this patch is doing two things at once:

1. Changing the costs of divides when not passing in the new Scalars parameter,
2. Changing the costs of divides when passing in a non-null Scalars.

It's probably worth splitting the changes up into two different PRs so we can see review them independently. It also allows us to monitor the performance impact of each change on it's own.

https://github.com/llvm/llvm-project/pull/118055