Gamma.cpp

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/*
 * Copyright 2026 Nico Reißmann <nico.reissmann@gmail.com>
 * See COPYING for terms of redistribution.
 */
 
#include <jlm/llvm/ir/operators/Gamma.hpp>
#include <jlm/llvm/ir/Trace.hpp>
#include <jlm/rvsdg/gamma.hpp>
#include <jlm/rvsdg/substitution.hpp>
 
namespace jlm::llvm
{
 
bool
reduceStaticallyKnownPredicate(rvsdg::GammaNode & gammaNode)
{
  const auto & tracedPredicate = llvm::traceOutput(*gammaNode.predicate()->origin());
  auto [ctlConstantNode, ctlConstantOperation] =
      rvsdg::TryGetSimpleNodeAndOptionalOp<rvsdg::ControlConstantOperation>(tracedPredicate);
  if (!ctlConstantOperation)
  {
    return false;
  }
 
  const auto ctlAlternative = ctlConstantOperation->value().alternative();
 
  rvsdg::SubstitutionMap smap;
  for (const auto & [input, branchArgument] : gammaNode.GetEntryVars())
    smap.insert(branchArgument[ctlAlternative], input->origin());
 
  gammaNode.subregion(ctlAlternative)->copy(gammaNode.region(), smap);
 
  for (auto [branchResult, output] : gammaNode.GetExitVars())
    output->divert_users(&smap.lookup(*branchResult[ctlAlternative]->origin()));
 
  remove(&gammaNode);
  return true;
}
 
}