legalize_vectorized_loop.cc

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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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 *
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/*!
 * \file layout_inference.cc
 * \brief infer the fragment/shared memory layout
 */

#include <tvm/ffi/reflection/registry.h>
#include <tvm/tir/builtin.h>
#include <tvm/tir/op.h>
#include <tvm/tir/stmt_functor.h>
#include <tvm/tir/transform.h>
#include <tvm/tir/utils.h>

#include <queue>

#include "../op/parallel.h"
#include "arith/ir_mutator_with_analyzer.h"
#include "loop_partition.h"
#include "loop_vectorize.h"

namespace tvm {
namespace tl {

using namespace tir;
using arith::IRMutatorWithAnalyzer;

// Class to legalize vectorized loops by transforming them appropriately
class LoopVectorizedLegalizer : IRMutatorWithAnalyzer {
public:
  // Static method to substitute and transform the given PrimFunc
  static PrimFunc Substitute(PrimFunc f) {
    arith::Analyzer analyzer;
    // Create an instance of the legalizer with the analyzer
    LoopVectorizedLegalizer substituter(&analyzer);
    // Get a mutable copy of the function node
    PrimFuncNode *fptr = f.CopyOnWrite();
    // Apply the legalizer to the function body
    fptr->body = substituter.VisitStmt(f->body);
    return f;
  }

private:
  // Constructor initializing the base class with the analyzer
  LoopVectorizedLegalizer(arith::Analyzer *analyzer)
      : arith::IRMutatorWithAnalyzer(analyzer) {}

  // Override the VisitStmt_ method to handle ForNode (loop statements)
  Stmt VisitStmt_(const ForNode *op) final {
    // Visit and potentially modify the loop node
    For for_node = Downcast<For>(IRMutatorWithAnalyzer::VisitStmt_(op));
    // If the loop is not vectorized, proceed with the default behavior
    if (for_node->kind != ForKind::kVectorized) {
      return IRMutatorWithAnalyzer::VisitStmt_(op);
    }
    // Change the loop kind from vectorized to serial
    for_node.CopyOnWrite()->kind = ForKind::kSerial;
    // Apply vectorization transformation to the loop
    return VectorizeLoop(for_node);
  }
};

// Create a pass that legalizes vectorized loops in the IRModule
tvm::transform::Pass LegalizeVectorizedLoop() {
  using namespace tir::transform;
  // Define the transformation function to be applied
  auto pass_func = [=](PrimFunc f, const IRModule &m, const PassContext &ctx) {
    return LoopVectorizedLegalizer::Substitute(std::move(f));
  };
  // Create and return a PrimFunc pass with the transformation function
  return CreatePrimFuncPass(pass_func, 0, "tl.LegalizeVectorizedLoop", {});
}

// Register the pass globally so it can be used in the compilation pipeline
TVM_FFI_STATIC_INIT_BLOCK({
  namespace refl = tvm::ffi::reflection;
  refl::GlobalDef().def("tl.transform.LegalizeVectorizedLoop",
                        LegalizeVectorizedLoop);
});

} // namespace tl
} // namespace tvm