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

[Sander de Smalen via llvm-commits]

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@@ -897,8 +898,9 @@ RecurrenceDescriptor::InstDesc RecurrenceDescriptor::isRecurrenceInstr(
   case Instruction::PHI:
     return InstDesc(I, Prev.getRecKind(), Prev.getExactFPMathInst());
   case Instruction::Sub:
+    return InstDesc(Kind == RecurKind::Sub, I);
   case Instruction::Add:
-    return InstDesc(Kind == RecurKind::Add, I);
+    return InstDesc(Kind == RecurKind::Add || Kind == RecurKind::Sub, I);
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sdesmalen-arm wrote:

Remove redundant condition:

```suggestion
    return InstDesc(Kind == RecurKind::Add, I);
```

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