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85bf12c584
valid itinerary but no pipeline stages. An itinerary can contain useful scheduling information without specifying pipeline stages for each instruction. llvm-svn: 157977
96 lines
3.5 KiB
C++
96 lines
3.5 KiB
C++
//=- llvm/CodeGen/ScheduleHazardRecognizer.h - Scheduling Support -*- C++ -*-=//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the ScheduleHazardRecognizer class, which implements
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// hazard-avoidance heuristics for scheduling.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
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#define LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
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namespace llvm {
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class SUnit;
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/// HazardRecognizer - This determines whether or not an instruction can be
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/// issued this cycle, and whether or not a noop needs to be inserted to handle
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/// the hazard.
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class ScheduleHazardRecognizer {
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protected:
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/// MaxLookAhead - Indicate the number of cycles in the scoreboard
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/// state. Important to restore the state after backtracking. Additionally,
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/// MaxLookAhead=0 identifies a fake recognizer, allowing the client to
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/// bypass virtual calls. Currently the PostRA scheduler ignores it.
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unsigned MaxLookAhead;
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public:
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ScheduleHazardRecognizer(): MaxLookAhead(0) {}
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virtual ~ScheduleHazardRecognizer();
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enum HazardType {
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NoHazard, // This instruction can be emitted at this cycle.
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Hazard, // This instruction can't be emitted at this cycle.
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NoopHazard // This instruction can't be emitted, and needs noops.
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};
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unsigned getMaxLookAhead() const { return MaxLookAhead; }
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bool isEnabled() const { return MaxLookAhead != 0; }
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/// atIssueLimit - Return true if no more instructions may be issued in this
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/// cycle.
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///
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/// FIXME: remove this once MachineScheduler is the only client.
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virtual bool atIssueLimit() const { return false; }
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/// getHazardType - Return the hazard type of emitting this node. There are
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/// three possible results. Either:
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/// * NoHazard: it is legal to issue this instruction on this cycle.
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/// * Hazard: issuing this instruction would stall the machine. If some
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/// other instruction is available, issue it first.
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/// * NoopHazard: issuing this instruction would break the program. If
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/// some other instruction can be issued, do so, otherwise issue a noop.
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virtual HazardType getHazardType(SUnit *m, int Stalls = 0) {
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return NoHazard;
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}
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/// Reset - This callback is invoked when a new block of
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/// instructions is about to be schedule. The hazard state should be
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/// set to an initialized state.
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virtual void Reset() {}
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/// EmitInstruction - This callback is invoked when an instruction is
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/// emitted, to advance the hazard state.
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virtual void EmitInstruction(SUnit *) {}
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/// AdvanceCycle - This callback is invoked whenever the next top-down
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/// instruction to be scheduled cannot issue in the current cycle, either
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/// because of latency or resource conflicts. This should increment the
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/// internal state of the hazard recognizer so that previously "Hazard"
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/// instructions will now not be hazards.
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virtual void AdvanceCycle() {}
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/// RecedeCycle - This callback is invoked whenever the next bottom-up
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/// instruction to be scheduled cannot issue in the current cycle, either
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/// because of latency or resource conflicts.
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virtual void RecedeCycle() {}
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/// EmitNoop - This callback is invoked when a noop was added to the
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/// instruction stream.
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virtual void EmitNoop() {
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// Default implementation: count it as a cycle.
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AdvanceCycle();
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}
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};
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}
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#endif
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