[llvm] [AArch64][CostModel] Consider the cost of const vector (PR #117539)

[Sushant Gokhale via llvm-commits]

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@@ -11019,8 +11039,6 @@ BoUpSLP::getEntryCost(const TreeEntry *E, ArrayRef<Value *> VectorizedVals,
 
   bool NeedToShuffleReuses = !E->ReuseShuffleIndices.empty();
   if (E->isGather()) {
-    if (allConstant(VL))
-      return 0;
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sushgokh wrote:

1. To say, `getConstantMatCost` in RISCV is not doing detailed analysis about the constants involved. Its very primitive in nature. For AArch64, I need to know about the constants involved.
2. If you are worried about tests failing for X86/RISCV/other targets by removing this check, this is not happening because I am returning 0 from some other place(i.e BasicTTI).

And in short, nothing is affected for other targets.

https://github.com/llvm/llvm-project/pull/117539