[llvm] [MachineSink] Add capability for aggressive loop sinking (PR #117247)

[Matt Arsenault via llvm-commits]

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@@ -771,32 +787,61 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
 
   if (SinkInstsIntoCycle) {
     SmallVector<MachineCycle *, 8> Cycles(CI->toplevel_cycles());
-    for (auto *Cycle : Cycles) {
-      MachineBasicBlock *Preheader = Cycle->getCyclePreheader();
-      if (!Preheader) {
-        LLVM_DEBUG(dbgs() << "CycleSink: Can't find preheader\n");
-        continue;
-      }
-      SmallVector<MachineInstr *, 8> Candidates;
-      FindCycleSinkCandidates(Cycle, Preheader, Candidates);
-
-      // Walk the candidates in reverse order so that we start with the use
-      // of a def-use chain, if there is any.
-      // TODO: Sort the candidates using a cost-model.
-      unsigned i = 0;
-      for (MachineInstr *I : llvm::reverse(Candidates)) {
-        if (i++ == SinkIntoCycleLimit) {
-          LLVM_DEBUG(dbgs() << "CycleSink:   Limit reached of instructions to "
-                               "be analysed.");
-          break;
+    SchedModel.init(STI);
+    enum CycleSinkStage { COPY, LOW_LATENCY, AGGRESSIVE, END };
+
+    CycleSinkStage Stage = CycleSinkStage::COPY;
+    bool HasHighPressure;
+    do {
+      HasHighPressure = false;
+      DenseMap<std::pair<MachineInstr *, MachineBasicBlock *>, MachineInstr *>
+          SunkInstrs;
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arsenm wrote:

Pull definition out of loop and clear the map each cycle?

https://github.com/llvm/llvm-project/pull/117247