[mlir] [flang] [clang-tools-extra] [libcxx] [clang] [llvm] [LV] Improve AnyOf reduction codegen. (PR #78304)

[via cfe-commits]

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@@ -9110,6 +9111,41 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
       continue;
 
     const RecurrenceDescriptor &RdxDesc = PhiR->getRecurrenceDescriptor();
+    // Adjust AnyOf reductions; replace the reduction phi for the selected value
+    // with a boolean reduction phi node to check if the condition is true in
+    // any iteration. The final value is selected by the final
+    // ComputeReductionResult.
+    if (RecurrenceDescriptor::isAnyOfRecurrenceKind(
+            RdxDesc.getRecurrenceKind())) {
+      auto *Select = cast<VPRecipeBase>(*find_if(PhiR->users(), [](VPUser *U) {
+        return isa<VPWidenSelectRecipe>(U) ||
+               (isa<VPReplicateRecipe>(U) &&
+                cast<VPReplicateRecipe>(U)->getUnderlyingInstr()->getOpcode() ==
+                    Instruction::Select);
+      }));
+      VPValue *Cmp = Select->getOperand(0);
+      // If the compare is checking the reduction PHI node, adjust it to check
+      // the start value.
+      if (VPRecipeBase *CmpR = Cmp->getDefiningRecipe()) {
+        for (unsigned I = 0; I != CmpR->getNumOperands(); ++I)
+          if (CmpR->getOperand(I) == PhiR)
+            CmpR->setOperand(I, PhiR->getStartValue());
+      }
+      VPBuilder::InsertPointGuard Guard(Builder);
+      Builder.setInsertPoint(Select);
+
+      // If the true value of the select is the reduction phi, the new value is
+      // selected if the negated condition is true in any iteration.
+      if (Select->getOperand(1) == PhiR)
+        Cmp = Builder.createNot(Cmp);
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ayalz wrote:

As Mel pointed out, this case of "Red = cond ? PhiR : Other" where a single false cond suffices for the result to be Other, could be considered an `AllOf` reduction starting with true using createAnd() instead of createOr(), resulting in "AND(conds) ? Start : Other".

Negating cond swaps the operands and translates into the "Red = !cond ? Other : PhiR" form of an `AnyOf` reduction starting with false and using createOr(), where a single true !cond suffices for the result to be Other, resulting in "OR(!conds) ? Other : Start".

https://github.com/llvm/llvm-project/pull/78304