[llvm] [LoopVectorize] LLVM fails to vectorise loops with multi-bool varables (PR #89226)

[Sander de Smalen via llvm-commits]

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@@ -635,14 +635,57 @@ RecurrenceDescriptor::isAnyOfPattern(Loop *Loop, PHINode *OrigPhi,
       return InstDesc(Select, Prev.getRecKind());
   }
 
+  SelectInst *SI = dyn_cast<SelectInst>(I);
+  Instruction *Cmp = nullptr;
+
+  if (SI) {
+    // Check that SelectInst is related to the this PHI reduction.
+    bool HasOrigPhiUser = false;
+    bool SelectNonPHIUserInLoop = false;
+    for (User *U : SI->users()) {
+      Instruction *Inst = dyn_cast<Instruction>(U);
+      if (!Inst)
+        continue;
+      if (Inst == OrigPhi) {
+        HasOrigPhiUser = true;
+      } else {
+        if (Loop->contains(Inst->getParent()))
+          SelectNonPHIUserInLoop = true;
+      }
+    }
+    Cmp = dyn_cast<CmpInst>(SI->getOperand(0));
+    // Checking the current CmpInst is safe as a recurrent reduction.
+    if (Cmp && !Cmp->hasOneUse() && HasOrigPhiUser && !SelectNonPHIUserInLoop) {
+      bool IsSafeCMP = true;
+      for (User *U : Cmp->users()) {
+        Instruction *UInst = dyn_cast<Instruction>(U);
+        if (!UInst)
+          continue;
+        if (SelectInst *SI1 = dyn_cast<SelectInst>(U)) {
+          if (!llvm::all_of(SI1->users(), [Loop](User *USI) {
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sdesmalen-arm wrote:

Having a loop that goes through all users of all users of the Compare seems rather expensive.

https://github.com/llvm/llvm-project/pull/89226