+//===----------------------------------------------------------------------===//
+// MacroFusion - DAG post-processing to encourage fusion of macro ops.
+//===----------------------------------------------------------------------===//
+
+namespace {
+/// \brief Post-process the DAG to create cluster edges between instructions
+/// that may be fused by the processor into a single operation.
+class MacroFusion : public ScheduleDAGMutation {
+ const TargetInstrInfo *TII;
+public:
+ MacroFusion(const TargetInstrInfo *tii): TII(tii) {}
+
+ virtual void apply(ScheduleDAGMI *DAG);
+};
+} // anonymous
+
+/// \brief Callback from DAG postProcessing to create cluster edges to encourage
+/// fused operations.
+void MacroFusion::apply(ScheduleDAGMI *DAG) {
+ // For now, assume targets can only fuse with the branch.
+ MachineInstr *Branch = DAG->ExitSU.getInstr();
+ if (!Branch)
+ return;
+
+ for (unsigned Idx = DAG->SUnits.size(); Idx > 0;) {
+ SUnit *SU = &DAG->SUnits[--Idx];
+ if (!TII->shouldScheduleAdjacent(SU->getInstr(), Branch))
+ continue;
+
+ // Create a single weak edge from SU to ExitSU. The only effect is to cause
+ // bottom-up scheduling to heavily prioritize the clustered SU. There is no
+ // need to copy predecessor edges from ExitSU to SU, since top-down
+ // scheduling cannot prioritize ExitSU anyway. To defer top-down scheduling
+ // of SU, we could create an artificial edge from the deepest root, but it
+ // hasn't been needed yet.
+ bool Success = DAG->addEdge(&DAG->ExitSU, SDep(SU, SDep::Cluster));
+ (void)Success;
+ assert(Success && "No DAG nodes should be reachable from ExitSU");
+
+ DEBUG(dbgs() << "Macro Fuse SU(" << SU->NodeNum << ")\n");
+ break;
+ }
+}
+