KanagawaEliminateRedundantOps.cpp

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//===- KanagawaEliminateRedundantOps.cpp ----------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include "circt/Dialect/Kanagawa/KanagawaDialect.h"
#include "circt/Dialect/Kanagawa/KanagawaOps.h"
#include "circt/Dialect/Kanagawa/KanagawaPasses.h"
#include "circt/Dialect/Kanagawa/KanagawaTypes.h"
 
#include "mlir/Pass/Pass.h"
 
#include "llvm/ADT/TypeSwitch.h"
#include "llvm/Support/Debug.h"
 
#define DEBUG_TYPE "kanagawa-eliminate-redundant-ops"
 
namespace circt {
namespace kanagawa {
#define GEN_PASS_DEF_KANAGAWAELIMINATEREDUNDANTOPS
#include "circt/Dialect/Kanagawa/KanagawaPasses.h.inc"
} // namespace kanagawa
} // namespace circt
 
using namespace circt;
using namespace kanagawa;
 
// Helper function to eliminate redundant GetPortOps in a container
static void eliminateRedundantGetPortOps(ContainerOp containerOp) {
  // Structure to track accesses to each port of each instance
  struct PortAccesses {
    GetPortOp getAsInput;
    GetPortOp getAsOutput;
  };
 
  llvm::DenseMap</*instance*/ Value,
                 /*portName*/ llvm::DenseMap<StringAttr, PortAccesses>>
      instancePortAccessMap;
 
  // Collect all GetPortOps and identify redundant ones
  llvm::SmallVector<GetPortOp> redundantOps;
 
  for (auto getPortOp : containerOp.getOps<GetPortOp>()) {
    PortAccesses &portAccesses =
        instancePortAccessMap[getPortOp.getInstance()]
                             [getPortOp.getPortSymbolAttr().getAttr()];
 
    if (getPortOp.getDirection() == Direction::Input) {
      if (portAccesses.getAsInput) {
        // Found redundant input GetPortOp - mark the current one for removal
        // and replace its uses with the existing one
        getPortOp.replaceAllUsesWith(portAccesses.getAsInput.getResult());
        redundantOps.push_back(getPortOp);
      } else {
        portAccesses.getAsInput = getPortOp;
      }
    } else {
      if (portAccesses.getAsOutput) {
        // Found redundant output GetPortOp - mark the current one for removal
        // and replace its uses with the existing one
        getPortOp.replaceAllUsesWith(portAccesses.getAsOutput.getResult());
        redundantOps.push_back(getPortOp);
      } else {
        portAccesses.getAsOutput = getPortOp;
      }
    }
  }
 
  // Remove all redundant GetPortOps
  for (auto redundantOp : redundantOps)
    redundantOp.erase();
}
 
// Helper function to eliminate redundant PortReadOps in a container
static void eliminateRedundantPortReadOps(ContainerOp containerOp) {
  // Map to track the first PortReadOp for each port being read from
  llvm::DenseMap<Value, PortReadOp> portFirstReadMap;
  llvm::SmallVector<PortReadOp> redundantOps;
 
  for (auto portReadOp : containerOp.getOps<PortReadOp>()) {
    Value portBeingRead =
        portReadOp.getPort(); // The port operand being read from
 
    if (auto existingRead = portFirstReadMap.lookup(portBeingRead)) {
      // Found redundant PortReadOp - mark the current one for removal
      // and replace its uses with the existing one
      portReadOp.replaceAllUsesWith(existingRead.getResult());
      redundantOps.push_back(portReadOp);
    } else {
      portFirstReadMap[portBeingRead] = portReadOp;
    }
  }
 
  // Remove all redundant PortReadOps
  for (auto redundantOp : redundantOps)
    redundantOp.erase();
}
 
namespace {
 
struct EliminateRedundantOpsPass
    : public circt::kanagawa::impl::KanagawaEliminateRedundantOpsBase<
          EliminateRedundantOpsPass> {
  void runOnOperation() override {
    ContainerOp containerOp = getOperation();
    eliminateRedundantGetPortOps(containerOp);
    eliminateRedundantPortReadOps(containerOp);
  }
};
 
} // anonymous namespace
 
std::unique_ptr<mlir::Pass> circt::kanagawa::createEliminateRedundantOpsPass() {
  return std::make_unique<EliminateRedundantOpsPass>();
}