[llvm] [AArch64] Add SVE patterns for [su]adalp with separate ADD. (PR #204796)

[Gaëtan Bossu via llvm-commits]

================
@@ -2598,6 +2598,31 @@ instCombineSVEVectorMlaU(InstCombiner &IC, IntrinsicInst &II) {
   return std::nullopt;
 }
 
+static std::optional<Instruction *>
+instCombineSVEPairwiseAddLong(InstCombiner &IC, IntrinsicInst &II) {
+  assert((II.getIntrinsicID() == Intrinsic::aarch64_sve_sadalp ||
+          II.getIntrinsicID() == Intrinsic::aarch64_sve_uadalp) &&
+         "Expected SADALP or UADALP intrinsic");
+
+  // We are looking for add(adalp(%pred, zeroinitializer, %in), %acc)
+  if (!II.hasOneUse() || !match(II.getArgOperand(1), m_Zero()))
+    return std::nullopt;
+
+  auto *User = dyn_cast<Instruction>(*II.user_begin());
+  Value *Acc;
+  if (!User || !match(User, m_c_Add(m_Specific(&II), m_Value(Acc))))
----------------
gbossu wrote:

I was more concerned about the fact the the only user might not be an `Instruction`, but I doubt we'll get an `Operator` use of our intrinsic.

https://github.com/llvm/llvm-project/pull/204796