[llvm] [SLP] Make getSameOpcode support interchangeable instructions. (PR #127450)

[Alexey Bataev via llvm-commits]

================
@@ -2447,42 +2679,44 @@ class BoUpSLP {
       ArgSize = isa<IntrinsicInst>(MainOp) ? IntrinsicNumOperands : NumOperands;
       OpsVec.resize(NumOperands);
       unsigned NumLanes = VL.size();
-      for (unsigned OpIdx = 0; OpIdx != NumOperands; ++OpIdx) {
+      for (unsigned OpIdx = 0; OpIdx != NumOperands; ++OpIdx)
         OpsVec[OpIdx].resize(NumLanes);
-        for (unsigned Lane = 0; Lane != NumLanes; ++Lane) {
-          assert((isa<Instruction>(VL[Lane]) || isa<PoisonValue>(VL[Lane])) &&
-                 "Expected instruction or poison value");
-          // 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.
-          if (isa<PoisonValue>(VL[Lane])) {
-            if (auto *EI = dyn_cast<ExtractElementInst>(MainOp)) {
-              if (OpIdx == 0) {
+      for (unsigned Lane = 0; Lane != NumLanes; ++Lane) {
----------------
alexey-bataev wrote:

```suggestion
      for (unsigned Lane : seq<unsigned>(NumLanes)) {
```


https://github.com/llvm/llvm-project/pull/127450