[llvm] [SLPVectorizer][X86] Free load cost for stores with constant pointers (PR #118016)

[Simon Pilgrim via llvm-commits]

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@@ -5157,8 +5157,9 @@ InstructionCost X86TTIImpl::getMemoryOpCost(unsigned Opcode, Type *Src,
 
   InstructionCost Cost = 0;
 
-  // Add a cost for constant load to vector.
-  if (Opcode == Instruction::Store && OpInfo.isConstant())
+  // Add a cost for constant load to vector, if pointer is not a constant.
+  if (auto *SI = dyn_cast_or_null<StoreInst>(I);
+      SI && !isa<Constant>(SI->getPointerOperand()) && OpInfo.isConstant())
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RKSimon wrote:

Looking at #111126 - shouldn't we be checking to see if `OpInfo.isUniform()` and adjusting the Type accordingly?

It looks like the test case thinks it has to load a `<20 x i64> splat(i64 1)` constant when it just has to load `<2 x i64> splat(i64 1)`

https://github.com/llvm/llvm-project/pull/118016