[llvm] [SLP]Initial support for copyable elements (non-schedulable only) (PR #140279)

[Simon Pilgrim via llvm-commits]

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@@ -9907,22 +10097,122 @@ class InstructionsCompatibilityAnalysis {
                                     const TargetLibraryInfo &TLI)
       : DT(DT), DL(DL), TTI(TTI), TLI(TLI) {}
 
+  InstructionsState
+  buildInstructionsState(ArrayRef<Value *> VL, const BoUpSLP &R,
+                         bool TryCopyableElementsVectorization,
+                         bool WithProfitabilityCheck = false) {
+    InstructionsState S = getSameOpcode(VL, TLI);
+    if (S)
+      return S;
+    if (!VectorizeCopyableElements || !TryCopyableElementsVectorization)
+      return S;
+    findAndSetMainInstruction(VL);
+    if (!MainOp)
+      return InstructionsState::invalid();
+    S = InstructionsState(MainOp, MainOp);
+    if (!WithProfitabilityCheck)
+      return S;
+    // Check if it is profitable to vectorize the instruction.
+    SmallVector<BoUpSLP::ValueList> Operands = buildOperands(S, VL);
+    if (VL.size() == 2) {
+      // Check if the operands allow better vectorization.
+      SmallVector<std::pair<Value *, Value *>, 4> Candidates;
+      Candidates.emplace_back(Operands[0][0], Operands[0][1]);
+      Candidates.emplace_back(Operands[1][0], Operands[1][1]);
+      if (isCommutative(MainOp)) {
+        Candidates.emplace_back(Operands[0][0], Operands[1][1]);
+        Candidates.emplace_back(Operands[1][0], Operands[0][1]);
+      }
+      // No good candidates - not profitable.
+      if (!R.findBestRootPair(Candidates,
+                              BoUpSLP::LookAheadHeuristics::ScoreSplat)) {
+        // Deeper analysis for 2 splats/constants.
+        SmallVector<std::pair<Value *, Value *>, 4> Candidates1, Candidates2;
+        Candidates1.emplace_back(Operands[0][0], Operands[0][1]);
+        Candidates2.emplace_back(Operands[1][0], Operands[1][1]);
+        bool Res =
+            R.findBestRootPair(Candidates1) && R.findBestRootPair(Candidates2);
+        if (!Res && isCommutative(MainOp)) {
+          Candidates1.clear();
+          Candidates2.clear();
+          Candidates1.emplace_back(Operands[0][0], Operands[1][1]);
+          Candidates2.emplace_back(Operands[1][0], Operands[0][1]);
+          Res = R.findBestRootPair(Candidates1) &&
+                R.findBestRootPair(Candidates2);
+        }
+        if (!Res)
+          return InstructionsState::invalid();
+      }
+    }
+    assert(Operands.size() == 2 && "Unexpected number of operands!");
+    unsigned CopyableNum =
+        count_if(VL, [&](Value *V) { return S.isCopyableElement(V); });
+    if (CopyableNum <= VL.size() / 2)
+      return S;
+    // Check profitability if number of copyables > VL.size() / 2.
+    // 1. Reorder operands for better matching.
+    if (isCommutative(MainOp)) {
+      for (auto &Ops : Operands) {
+        // Make instructions the first operands.
+        if (isa<Instruction>(Ops.back())) {
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RKSimon wrote:

so we always commute even if front() is already an Instruction?

https://github.com/llvm/llvm-project/pull/140279