[llvm] [SLP] Vectorize zero-tested OR/UMax reductions (PR #205473)

[Alexey Bataev via llvm-commits]

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@@ -28744,6 +28757,159 @@ class HorizontalReduction {
            (match(I, m_LogicalAnd()) || match(I, m_LogicalOr()));
   }
 
+  /// Match an OR/UMax reduction whose only use is an equality compare against
+  /// zero, for example:
+  ///   %r = call iN @llvm.vector.reduce.or/umax(...)
+  ///   %c = icmp eq/ne iN %r, 0
+  ///
+  /// this is an all-zero / any-nonzero test of the reduced input lanes.
+  std::optional<ReductionZeroTestInfo> matchReductionZeroTestUse() const {
+    auto *Root = dyn_cast<Instruction>(ReductionRoot);
+    if (!Root || !Root->getType()->isIntegerTy() || !Root->hasOneUse() ||
+        (RdxKind != RecurKind::Or && RdxKind != RecurKind::UMax))
+      return std::nullopt;
+
+    auto *Cmp = dyn_cast<ICmpInst>(*Root->user_begin());
+    CmpPredicate Pred;
+    if (!Cmp || !match(Cmp, m_c_ICmp(Pred, m_Specific(Root), m_ZeroInt())) ||
+        !ICmpInst::isEquality(Pred))
+      return std::nullopt;
+
+    return ReductionZeroTestInfo{Cmp, Pred};
+  }
+
+  /// Cost the boolean-vector form of a reduction zero-test:
+  ///   %cmp = icmp eq/ne <N x Ty> %v, zeroinitializer
+  ///   %r   = call i1 @llvm.vector.reduce.and/or.vNi1(%cmp)
+  ///
+  /// `eq` uses reduce.and for an all-zero test, while `ne` uses reduce.or for
+  /// an any-nonzero test.
+  static InstructionCost
+  getBoolReductionZeroTestCost(const TargetTransformInfo &TTI,
+                               FixedVectorType *VecTy, CmpPredicate Pred,
+                               TTI::TargetCostKind CostKind) {
+    auto *CmpTy = cast<VectorType>(CmpInst::makeCmpResultType(VecTy));
+    unsigned ReductionOpcode =
+        Pred == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
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alexey-bataev wrote:

Weak check, need to check explcitily for ICmpInst::ICMP_NE

https://github.com/llvm/llvm-project/pull/205473