mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-07-08 18:30:04 +00:00
0a39d4e4c8
The Hazard checker implements in-order contraints, or interlocked resources. Ready instructions with hazards do not enter the available queue and are not visible to other heuristics. The major code change is the addition of SchedBoundary to encapsulate the state at the top or bottom of the schedule, including both a pending and available queue. The scheduler now counts cycles in sync with the hazard checker. These are minimum cycle counts based on known hazards. Targets with no itinerary (x86_64) currently remain at cycle 0. To fix this, we need to provide some maximum issue width for all targets. We also need to add the concept of expected latency vs. minimum latency. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157427 91177308-0d34-0410-b5e6-96231b3b80d8
94 lines
3.5 KiB
C++
94 lines
3.5 KiB
C++
//=- llvm/CodeGen/ScheduleHazardRecognizer.h - Scheduling Support -*- C++ -*-=//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the ScheduleHazardRecognizer class, which implements
|
|
// hazard-avoidance heuristics for scheduling.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
|
|
#define LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
|
|
|
|
namespace llvm {
|
|
|
|
class SUnit;
|
|
|
|
/// HazardRecognizer - This determines whether or not an instruction can be
|
|
/// issued this cycle, and whether or not a noop needs to be inserted to handle
|
|
/// the hazard.
|
|
class ScheduleHazardRecognizer {
|
|
protected:
|
|
/// MaxLookAhead - Indicate the number of cycles in the scoreboard
|
|
/// state. Important to restore the state after backtracking. Additionally,
|
|
/// MaxLookAhead=0 identifies a fake recognizer, allowing the client to
|
|
/// bypass virtual calls. Currently the PostRA scheduler ignores it.
|
|
unsigned MaxLookAhead;
|
|
|
|
public:
|
|
ScheduleHazardRecognizer(): MaxLookAhead(0) {}
|
|
virtual ~ScheduleHazardRecognizer();
|
|
|
|
enum HazardType {
|
|
NoHazard, // This instruction can be emitted at this cycle.
|
|
Hazard, // This instruction can't be emitted at this cycle.
|
|
NoopHazard // This instruction can't be emitted, and needs noops.
|
|
};
|
|
|
|
unsigned getMaxLookAhead() const { return MaxLookAhead; }
|
|
|
|
bool isEnabled() const { return MaxLookAhead != 0; }
|
|
|
|
/// atIssueLimit - Return true if no more instructions may be issued in this
|
|
/// cycle.
|
|
virtual bool atIssueLimit() const { return false; }
|
|
|
|
/// getHazardType - Return the hazard type of emitting this node. There are
|
|
/// three possible results. Either:
|
|
/// * NoHazard: it is legal to issue this instruction on this cycle.
|
|
/// * Hazard: issuing this instruction would stall the machine. If some
|
|
/// other instruction is available, issue it first.
|
|
/// * NoopHazard: issuing this instruction would break the program. If
|
|
/// some other instruction can be issued, do so, otherwise issue a noop.
|
|
virtual HazardType getHazardType(SUnit *m, int Stalls = 0) {
|
|
return NoHazard;
|
|
}
|
|
|
|
/// Reset - This callback is invoked when a new block of
|
|
/// instructions is about to be schedule. The hazard state should be
|
|
/// set to an initialized state.
|
|
virtual void Reset() {}
|
|
|
|
/// EmitInstruction - This callback is invoked when an instruction is
|
|
/// emitted, to advance the hazard state.
|
|
virtual void EmitInstruction(SUnit *) {}
|
|
|
|
/// AdvanceCycle - This callback is invoked whenever the next top-down
|
|
/// instruction to be scheduled cannot issue in the current cycle, either
|
|
/// because of latency or resource conflicts. This should increment the
|
|
/// internal state of the hazard recognizer so that previously "Hazard"
|
|
/// instructions will now not be hazards.
|
|
virtual void AdvanceCycle() {}
|
|
|
|
/// RecedeCycle - This callback is invoked whenever the next bottom-up
|
|
/// instruction to be scheduled cannot issue in the current cycle, either
|
|
/// because of latency or resource conflicts.
|
|
virtual void RecedeCycle() {}
|
|
|
|
/// EmitNoop - This callback is invoked when a noop was added to the
|
|
/// instruction stream.
|
|
virtual void EmitNoop() {
|
|
// Default implementation: count it as a cycle.
|
|
AdvanceCycle();
|
|
}
|
|
};
|
|
|
|
}
|
|
|
|
#endif
|