[llvm] [LV] Vectorize conditional scalar assignments (PR #158088)

[Benjamin Maxwell via llvm-commits]

================
@@ -712,6 +714,27 @@ RecurrenceDescriptor::isFindIVPattern(RecurKind Kind, Loop *TheLoop,
                                      m_Value(NonRdxPhi)))))
     return InstDesc(false, I);
 
+  if (isFindLastRecurrenceKind(Kind)) {
+    // Must be an integer scalar.
+    Type *Type = OrigPhi->getType();
+    if (!Type->isIntegerTy() && !Type->isPointerTy())
+      return InstDesc(false, I);
+
+    // FIXME: Support more complex patterns, including multiple selects.
+    // Phi or Select must be used only outside the loop,
+    // except for each other.
+    if (!all_of(I->users(), [OrigPhi, TheLoop](User *U) {
+          if (U == OrigPhi)
+            return true;
+          if (auto *UI = dyn_cast<Instruction>(U))
+            return !TheLoop->contains(UI);
+          return false;
+        }))
+      return InstDesc(false, I);
----------------
MacDue wrote:

nit: I think this can be simplified to:
```suggestion
    for (User* U : I->users()) {
      if (U == OrigPhi)
        continue;
      if (auto *UI = dyn_cast<Instruction>(U); UI && !TheLoop->contains(UI))
        continue;
      return InstDesc(false, I);
    }
```

https://github.com/llvm/llvm-project/pull/158088