[llvm] [SLP] Make getSameOpcode support different instructions if they have same semantics. (PR #112181)

[Han-Kuan Chen via llvm-commits]

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@@ -2335,24 +2479,41 @@ class BoUpSLP {
                                  : cast<Instruction>(VL[0])->getNumOperands();
       OpsVec.resize(NumOperands);
       unsigned NumLanes = VL.size();
-      for (unsigned OpIdx = 0; OpIdx != NumOperands; ++OpIdx) {
+      InstructionsState S = getSameOpcode(VL, TLI);
+      for (unsigned OpIdx : seq<unsigned>(NumOperands))
         OpsVec[OpIdx].resize(NumLanes);
-        for (unsigned Lane = 0; Lane != NumLanes; ++Lane) {
-          assert(isa<Instruction>(VL[Lane]) && "Expected instruction");
-          // Our tree has just 3 nodes: the root and two operands.
-          // It is therefore trivial to get the APO. We only need to check the
-          // opcode of VL[Lane] and whether the operand at OpIdx is the LHS or
-          // RHS operand. The LHS operand of both add and sub is never attached
-          // to an inversese operation in the linearized form, therefore its APO
-          // is false. The RHS is true only if VL[Lane] is an inverse operation.
-
-          // Since operand reordering is performed on groups of commutative
-          // operations or alternating sequences (e.g., +, -), we can safely
-          // tell the inverse operations by checking commutativity.
-          bool IsInverseOperation = !isCommutative(cast<Instruction>(VL[Lane]));
+      for (auto [I, V] : enumerate(VL)) {
+        assert(isa<Instruction>(V) && "Expected instruction");
+        SmallVector<InterchangeableInstruction> IIList =
+            getInterchangeableInstruction(cast<Instruction>(V));
+        Value *SelectedOp;
+        auto Iter = find_if(IIList, [&](const InterchangeableInstruction &II) {
+          return II.Opcode == S.MainOp->getOpcode();
+        });
+        if (Iter == IIList.end()) {
+          Iter = find_if(IIList, [&](const InterchangeableInstruction &II) {
+            return II.Opcode == S.AltOp->getOpcode();
+          });
+          SelectedOp = S.AltOp;
+        } else {
+          SelectedOp = S.MainOp;
+        }
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HanKuanChen wrote:

Any examples? Cannot image how to modify `getInterchangeableInstruction`.

https://github.com/llvm/llvm-project/pull/112181