[llvm] [AArch64][CostModel] Alter sdiv/srem cost where the divisor is constant (PR #123552)

[Sushant Gokhale via llvm-commits]

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@@ -5,29 +5,29 @@ target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
 
 define i32 @srem() {
 ; CHECK-LABEL: 'srem'
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 14 for instruction: %I128 = srem i128 undef, undef
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sushgokh wrote:

just to resolve this, I have 2 questions @davemgreen :
1. why do you need this check?
`(Ty->isVectorTy() && (ISD == ISD::SDIV || ISD == ISD::UDIV))`
urem/srem costs are going to be similar to those of udiv/sdiv respectively.

2. > to make sure that the non-constant versions are not affected

We can assume certain constant value for undef, right?

https://github.com/llvm/llvm-project/pull/123552