[llvm] [AMDGPU] Introduce iglp_opt(2): Generalized exp/mfma interleaving for select kernels (PR #81342)

[Austin Kerbow via llvm-commits]

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@@ -902,6 +904,926 @@ void MFMASmallGemmOpt::applyIGLPStrategy(
         SchedGroupMask::MFMA, 1, PipelineSyncID, DAG, TII);
     SG->initSchedGroup(SyncedInstrs[SG->getSyncID()]);
   }
+
+  return true;
+}
+
+class MFMAExpInterleaveOpt final : public IGLPStrategy {
+private:
+  // The count of TRANS SUs involved in the interleaved pipeline
+  static unsigned TransPipeCount;
+  // The count of MFMA SUs involved in the interleaved pipeline
+  static unsigned MFMAPipeCount;
+  // The number of transitive MFMA successors for each TRANS SU
+  static unsigned MFMAEnablement;
+  // The number of transitive TRANS predecessors for each MFMA SU
+  static unsigned ExpRequirement;
+  // The count of independent "chains" of MFMA instructions in the pipeline
+  static unsigned MFMAChains;
+  // The length of each independent "chain" of MFMA instructions
+  static unsigned MFMAChainLength;
+  // Whether or not the pipeline has V_CVT instructions
+  static bool HasCvt;
+  // Whether or not there are instructions between the TRANS instruction and
+  // V_CVT
+  static bool HasChainBetweenCvt;
+  // The first occuring DS_READ which feeds an MFMA chain
+  static std::optional<unsigned> FirstPipeDSR;
+  SmallVector<SUnit *, 4> MFMAChainSeeds;
+  // Compute the heuristics for the pipeline, returning whether or not the DAG
+  // is well formatted for the mutation
+  bool analyzeDAG(const SIInstrInfo *TII);
+
+  /// Whether or not the instruction is a transitive predecessor of an MFMA
+  /// instruction
+  class IsPipeExp final : public InstructionRule {
+  public:
+    bool apply(const SUnit *SU, const ArrayRef<SUnit *> Collection,
+               SmallVectorImpl<SchedGroup> &SyncPipe) override {
+
+      auto DAG = SyncPipe[0].DAG;
+      auto TII = SyncPipe[0].TII;
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kerbowa wrote:

Doesn't `InstructionRule` already have TII?

https://github.com/llvm/llvm-project/pull/81342