[llvm] [LV] Create in-loop sub reductions (PR #147026)

[Sander de Smalen via llvm-commits]

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@@ -24345,6 +24348,8 @@ bool SLPVectorizerPass::tryToVectorize(Instruction *I, BoUpSLP &R) {
                                                CostKind);
       break;
     }
+    case RecurKind::Sub:
+      llvm_unreachable("Unexpected recurrence kind.");
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sdesmalen-arm wrote:

nit: I think you can remove this unreachable, because lots of other unsupported recurrence kinds are handled safely here by returning `false`.

https://github.com/llvm/llvm-project/pull/147026