[llvm] [AMDGPU] Add iglp_opt(3) for simple mfma / exp interleaving (PR #117269)

[Matt Arsenault via llvm-commits]

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@@ -1845,6 +1846,50 @@ bool MFMAExpInterleaveOpt::applyIGLPStrategy(
   return true;
 }
 
+class MFMAExpSimpleInterleaveOpt final : public IGLPStrategy {
+private:
+public:
+  bool applyIGLPStrategy(
+      DenseMap<int, SUnitsToCandidateSGsMap> &SyncedInstrs,
+      DenseMap<int, SmallVector<SchedGroup, 4>> &SyncedSchedGroups,
+      AMDGPU::SchedulingPhase Phase) override;
+
+  bool shouldApplyStrategy(ScheduleDAGInstrs *DAG,
+                           AMDGPU::SchedulingPhase Phase) override {
+    return true;
+  }
+
+  MFMAExpSimpleInterleaveOpt(ScheduleDAGInstrs *DAG, const SIInstrInfo *TII)
+      : IGLPStrategy(DAG, TII) {
+    IsBottomUp = true;
+  }
+};
+
+bool MFMAExpSimpleInterleaveOpt::applyIGLPStrategy(
+    DenseMap<int, SUnitsToCandidateSGsMap> &SyncedInstrs,
+    DenseMap<int, SmallVector<SchedGroup, 4>> &SyncedSchedGroups,
+    AMDGPU::SchedulingPhase Phase) {
+  // Count the number of MFMA instructions.
+  unsigned MFMACount = 0;
+  for (const MachineInstr &I : *DAG)
+    if (TII->isMFMAorWMMA(I))
+      ++MFMACount;
+
+  const unsigned PipelineSyncID = 0;
+  SchedGroup *SG = nullptr;
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arsenm wrote:

No sense in making this a free variable, just declare and initialize separate variables in the 2 individual uses 

https://github.com/llvm/llvm-project/pull/117269