#include <algorithm>
#include <chrono>
#include <iostream>
#include <set>
#include <sstream>

#include "Lower.h"

#include "AddAtomicMutex.h"
#include "AddImageChecks.h"
#include "AddParameterChecks.h"
#include "AllocationBoundsInference.h"
#include "AsyncProducers.h"
#include "BoundSmallAllocations.h"
#include "Bounds.h"
#include "BoundsInference.h"
#include "CSE.h"
#include "CanonicalizeGPUVars.h"
#include "ClampUnsafeAccesses.h"
#include "CompilerLogger.h"
#include "Debug.h"
#include "DebugArguments.h"
#include "DebugToFile.h"
#include "Deinterleave.h"
#include "EarlyFree.h"
#include "ExtractTileOperations.h"
#include "FindCalls.h"
#include "FindIntrinsics.h"
#include "FlattenNestedRamps.h"
#include "Func.h"
#include "Function.h"
#include "FuseGPUThreadLoops.h"
#include "FuzzFloatStores.h"
#include "HexagonOffload.h"
#include "IRMutator.h"
#include "IROperator.h"
#include "IRPrinter.h"
#include "InferArguments.h"
#include "InjectHostDevBufferCopies.h"
#include "Inline.h"
#include "LICM.h"
#include "LoopCarry.h"
#include "LowerParallelTasks.h"
#include "LowerWarpShuffles.h"
#include "Memoization.h"
#include "OffloadGPULoops.h"
#include "PartitionLoops.h"
#include "Prefetch.h"
#include "Profiling.h"
#include "PurifyIndexMath.h"
#include "Qualify.h"
#include "RealizationOrder.h"
#include "RebaseLoopsToZero.h"
#include "RemoveDeadAllocations.h"
#include "RemoveExternLoops.h"
#include "RemoveUndef.h"
#include "ScheduleFunctions.h"
#include "SelectGPUAPI.h"
#include "Simplify.h"
#include "SimplifyCorrelatedDifferences.h"
#include "SimplifySpecializations.h"
#include "SkipStages.h"
#include "SlidingWindow.h"
#include "SplitTuples.h"
#include "StageStridedLoads.h"
#include "StorageFlattening.h"
#include "StorageFolding.h"
#include "StrictifyFloat.h"
#include "Substitute.h"
#include "Tracing.h"
#include "TrimNoOps.h"
#include "UnifyDuplicateLets.h"
#include "UniquifyVariableNames.h"
#include "UnpackBuffers.h"
#include "UnrollLoops.h"
#include "UnsafePromises.h"
#include "VectorizeLoops.h"
#include "WrapCalls.h"

namespace Halide {
namespace Internal {

using std::ostringstream;
using std::string;
using std::vector;

namespace {

class LoweringLogger {
 Stmt last_written;

public:
 void operator()(const string &message, const Stmt &s) {
 if (!s.same_as(last_written)) {
 debug(2) << message << "\n"
 << s << "\n";
 last_written = s;
 } else {
 debug(2) << message << " (unchanged)\n\n";
 }
 }
};

void lower_impl(const vector<Function> &output_funcs,
 const string &pipeline_name,
 const Target &t,
 const vector<Argument> &args,
 const LinkageType linkage_type,
 const vector<Stmt> &requirements,
 bool trace_pipeline,
 const vector<IRMutator *> &custom_passes,
 Module &result_module) {
 auto time_start = std::chrono::high_resolution_clock::now();

 size_t initial_lowered_function_count = result_module.functions().size();

 // Create a deep-copy of the entire graph of Funcs.
 auto [outputs, env] = deep_copy(output_funcs, build_environment(output_funcs));

 bool any_strict_float = strictify_float(env, t);
 result_module.set_any_strict_float(any_strict_float);

 // Output functions should all be computed and stored at root.
 for (const Function &f : outputs) {
 Func(f).compute_root().store_root();
 }

 // Finalize all the LoopLevels
 for (auto &iter : env) {
 iter.second.lock_loop_levels();
 }

 // Substitute in wrapper Funcs
 env = wrap_func_calls(env);

 // Compute a realization order and determine group of functions which loops
 // are to be fused together
 auto [order, fused_groups] = realization_order(outputs, env);

 // Try to simplify the RHS/LHS of a function definition by propagating its
 // specializations' conditions
 simplify_specializations(env);

 LoweringLogger log;

 debug(1) << "Creating initial loop nests...\n";
 bool any_memoized = false;
 Stmt s = schedule_functions(outputs, fused_groups, env, t, any_memoized);
 log("Lowering after creating initial loop nests:", s);

 if (any_memoized) {
 debug(1) << "Injecting memoization...\n";
 s = inject_memoization(s, env, pipeline_name, outputs);
 log("Lowering after injecting memoization:", s);
 } else {
 debug(1) << "Skipping injecting memoization...\n";
 }
 debug(1) << "Injecting tracing...\n";
 s = inject_tracing(s, pipeline_name, trace_pipeline, env, outputs, t);
 log("Lowering after injecting tracing:", s);

 debug(1) << "Adding checks for parameters\n";
 s = add_parameter_checks(requirements, s, t);
 log("Lowering after injecting parameter checks:", s);

 // Compute the maximum and minimum possible value of each
 // function. Used in later bounds inference passes.
 debug(1) << "Computing bounds of each function's value\n";
 FuncValueBounds func_bounds = compute_function_value_bounds(order, env);

 // Clamp unsafe instances where a Func f accesses a Func g using
 // an index which depends on a third Func h.
 debug(1) << "Clamping unsafe data-dependent accesses\n";
 s = clamp_unsafe_accesses(s, env, func_bounds);
 log("Lowering after clamping unsafe data-dependent accesses", s);

 // This pass injects nested definitions of variable names, so we
 // can't simplify statements from here until we fix them up. (We
 // can still simplify Exprs).
 debug(1) << "Performing computation bounds inference...\n";
 s = bounds_inference(s, outputs, order, fused_groups, env, func_bounds, t);
 log("Lowering after computation bounds inference:", s);

 debug(1) << "Removing extern loops...\n";
 s = remove_extern_loops(s);
 log("Lowering after removing extern loops:", s);

 debug(1) << "Performing sliding window optimization...\n";
 s = sliding_window(s, env);
 log("Lowering after sliding window:", s);

 // This uniquifies the variable names, so we're good to simplify
 // after this point. This lets later passes assume syntactic
 // equivalence means semantic equivalence.
 debug(1) << "Uniquifying variable names...\n";
 s = uniquify_variable_names(s);
 log("Lowering after uniquifying variable names:", s);

 debug(1) << "Simplifying...\n";
 s = simplify(s, false); // Storage folding and allocation bounds inference needs .loop_max symbols
 log("Lowering after first simplification:", s);

 debug(1) << "Simplifying correlated differences...\n";
 s = simplify_correlated_differences(s);
 log("Lowering after simplifying correlated differences:", s);

 debug(1) << "Performing allocation bounds inference...\n";
 s = allocation_bounds_inference(s, env, func_bounds);
 log("Lowering after allocation bounds inference:", s);

 bool will_inject_host_copies =
 (t.has_gpu_feature() ||
 t.has_feature(Target::OpenGLCompute) ||
 t.has_feature(Target::HexagonDma) ||
 (t.arch != Target::Hexagon && (t.has_feature(Target::HVX))));

 debug(1) << "Adding checks for images\n";
 s = add_image_checks(s, outputs, t, order, env, func_bounds, will_inject_host_copies);
 log("Lowering after injecting image checks:", s);

 debug(1) << "Removing code that depends on undef values...\n";
 s = remove_undef(s);
 log("Lowering after removing code that depends on undef values:", s);

 debug(1) << "Performing storage folding optimization...\n";
 s = storage_folding(s, env);
 log("Lowering after storage folding:", s);

 debug(1) << "Injecting debug_to_file calls...\n";
 s = debug_to_file(s, outputs, env);
 log("Lowering after injecting debug_to_file calls:", s);

 debug(1) << "Injecting prefetches...\n";
 s = inject_prefetch(s, env);
 log("Lowering after injecting prefetches:", s);

 debug(1) << "Discarding safe promises...\n";
 s = lower_safe_promises(s);
 log("Lowering after discarding safe promises:", s);

 debug(1) << "Dynamically skipping stages...\n";
 s = skip_stages(s, order);
 log("Lowering after dynamically skipping stages:", s);

 debug(1) << "Forking asynchronous producers...\n";
 s = fork_async_producers(s, env);
 log("Lowering after forking asynchronous producers:", s);

 debug(1) << "Destructuring tuple-valued realizations...\n";
 s = split_tuples(s, env);
 log("Lowering after destructuring tuple-valued realizations:", s);

 // OpenGL relies on GPU var canonicalization occurring before
 // storage flattening.
 if (t.has_gpu_feature() ||
 t.has_feature(Target::OpenGLCompute)) {
 debug(1) << "Canonicalizing GPU var names...\n";
 s = canonicalize_gpu_vars(s);
 log("Lowering after canonicalizing GPU var names:", s);
 }

 debug(1) << "Bounding small realizations...\n";
 s = simplify_correlated_differences(s);
 s = bound_small_allocations(s);
 log("Lowering after bounding small realizations:", s);

 debug(1) << "Performing storage flattening...\n";
 s = storage_flattening(s, outputs, env, t);
 log("Lowering after storage flattening:", s);

 debug(1) << "Adding atomic mutex allocation...\n";
 s = add_atomic_mutex(s, env);
 log("Lowering after adding atomic mutex allocation:", s);

 debug(1) << "Unpacking buffer arguments...\n";
 s = unpack_buffers(s);
 log("Lowering after unpacking buffer arguments:", s);

 if (any_memoized) {
 debug(1) << "Rewriting memoized allocations...\n";
 s = rewrite_memoized_allocations(s, env);
 log("Lowering after rewriting memoized allocations:", s);
 } else {
 debug(1) << "Skipping rewriting memoized allocations...\n";
 }

 if (will_inject_host_copies) {
 debug(1) << "Selecting a GPU API for GPU loops...\n";
 s = select_gpu_api(s, t);
 log("Lowering after selecting a GPU API:", s);

 debug(1) << "Injecting host <-> dev buffer copies...\n";
 s = inject_host_dev_buffer_copies(s, t);
 log("Lowering after injecting host <-> dev buffer copies:", s);

 debug(1) << "Selecting a GPU API for extern stages...\n";
 s = select_gpu_api(s, t);
 log("Lowering after selecting a GPU API for extern stages:", s);
 }

 debug(1) << "Simplifying...\n";
 s = simplify(s);
 s = unify_duplicate_lets(s);
 log("Lowering after second simplifcation:", s);

 debug(1) << "Reduce prefetch dimension...\n";
 s = reduce_prefetch_dimension(s, t);
 log("Lowering after reduce prefetch dimension:", s);

 debug(1) << "Simplifying correlated differences...\n";
 s = simplify_correlated_differences(s);
 log("Lowering after simplifying correlated differences:", s);

 debug(1) << "Unrolling...\n";
 s = unroll_loops(s);
 log("Lowering after unrolling:", s);

 debug(1) << "Vectorizing...\n";
 s = vectorize_loops(s, env);
 s = simplify(s);
 log("Lowering after vectorizing:", s);

 if (t.has_gpu_feature() ||
 t.has_feature(Target::OpenGLCompute)) {
 debug(1) << "Injecting per-block gpu synchronization...\n";
 s = fuse_gpu_thread_loops(s);
 log("Lowering after injecting per-block gpu synchronization:", s);
 }

 debug(1) << "Detecting vector interleavings...\n";
 s = rewrite_interleavings(s);
 s = simplify(s);
 log("Lowering after rewriting vector interleavings:", s);

 debug(1) << "Partitioning loops to simplify boundary conditions...\n";
 s = partition_loops(s);
 s = simplify(s);
 log("Lowering after partitioning loops:", s);

 debug(1) << "Staging strided loads...\n";
 s = stage_strided_loads(s);
 log("Lowering after staging strided loads:", s);

 debug(1) << "Trimming loops to the region over which they do something...\n";
 s = trim_no_ops(s);
 log("Lowering after loop trimming:", s);

 debug(1) << "Rebasing loops to zero...\n";
 s = rebase_loops_to_zero(s);
 debug(2) << "Lowering after rebasing loops to zero:\n"
 << s << "\n\n";

 debug(1) << "Hoisting loop invariant if statements...\n";
 s = hoist_loop_invariant_if_statements(s);
 log("Lowering after hoisting loop invariant if statements:", s);

 debug(1) << "Injecting early frees...\n";
 s = inject_early_frees(s);
 log("Lowering after injecting early frees:", s);

 if (t.has_feature(Target::FuzzFloatStores)) {
 debug(1) << "Fuzzing floating point stores...\n";
 s = fuzz_float_stores(s);
 log("Lowering after fuzzing floating point stores:", s);
 }

 debug(1) << "Simplifying correlated differences...\n";
 s = simplify_correlated_differences(s);
 log("Lowering after simplifying correlated differences:", s);

 debug(1) << "Bounding small allocations...\n";
 s = bound_small_allocations(s);
 log("Lowering after bounding small allocations:", s);

 if (t.has_feature(Target::Profile) || t.has_feature(Target::ProfileByTimer)) {
 debug(1) << "Injecting profiling...\n";
 s = inject_profiling(s, pipeline_name);
 log("Lowering after injecting profiling:", s);
 }

 if (t.has_feature(Target::CUDA)) {
 debug(1) << "Injecting warp shuffles...\n";
 s = lower_warp_shuffles(s, t);
 log("Lowering after injecting warp shuffles:", s);
 }

 debug(1) << "Simplifying...\n";
 s = common_subexpression_elimination(s);

 debug(1) << "Lowering unsafe promises...\n";
 s = lower_unsafe_promises(s, t);
 log("Lowering after lowering unsafe promises:", s);

 if (t.has_feature(Target::AVX512_SapphireRapids)) {
 debug(1) << "Extracting tile operations...\n";
 s = extract_tile_operations(s);
 log("Lowering after extracting tile operations:", s);
 }

 debug(1) << "Flattening nested ramps...\n";
 s = flatten_nested_ramps(s);
 log("Lowering after flattening nested ramps:", s);

 debug(1) << "Removing dead allocations and moving loop invariant code...\n";
 s = remove_dead_allocations(s);
 s = simplify(s);
 s = hoist_loop_invariant_values(s);
 s = hoist_loop_invariant_if_statements(s);
 log("Lowering after removing dead allocations and hoisting loop invariants:", s);

 debug(1) << "Finding intrinsics...\n";
 // Must be run after the last simplification, because it turns
 // divisions into shifts, which the simplifier reverses.
 s = find_intrinsics(s);
 log("Lowering after finding intrinsics:", s);

 debug(1) << "Hoisting prefetches...\n";
 s = hoist_prefetches(s);
 log("Lowering after hoisting prefetches:", s);

 debug(1) << "Lowering after final simplification:\n"
 << s << "\n\n";

 if (!custom_passes.empty()) {
 for (size_t i = 0; i < custom_passes.size(); i++) {
 debug(1) << "Running custom lowering pass " << i << "...\n";
 s = custom_passes[i]->mutate(s);
 debug(1) << "Lowering after custom pass " << i << ":\n"
 << s << "\n\n";
 }
 }

 if (t.arch != Target::Hexagon && t.has_feature(Target::HVX)) {
 debug(1) << "Splitting off Hexagon offload...\n";
 s = inject_hexagon_rpc(s, t, result_module);
 debug(2) << "Lowering after splitting off Hexagon offload:\n"
 << s << "\n";
 } else {
 debug(1) << "Skipping Hexagon offload...\n";
 }

 if (t.has_gpu_feature()) {
 debug(1) << "Offloading GPU loops...\n";
 s = inject_gpu_offload(s, t);
 debug(2) << "Lowering after splitting off GPU loops:\n"
 << s << "\n\n";
 } else {
 debug(1) << "Skipping GPU offload...\n";
 }

 // TODO: This needs to happen before lowering parallel tasks, because global
 // images used inside parallel loops are rewritten from loads from images to
 // loads from closure parameters. Closure parameters are missing the Buffer<>
 // object, which needs to be found by infer_arguments here. Running
 // infer_arguments prior to lower_parallel_tasks is a hacky solution to this
 // problem. It would be better if closures could directly reference globals
 // so they don't add overhead to the closure.
 vector<InferredArgument> inferred_args = infer_arguments(s, outputs);

 std::vector<LoweredFunc> closure_implementations;
 debug(1) << "Lowering Parallel Tasks...\n";
 s = lower_parallel_tasks(s, closure_implementations, pipeline_name, t);
 // Process any LoweredFunctions added by other passes. In practice, this
 // will likely not work well enough due to ordering issues with
 // closure generating passes and instead all such passes will need to
 // be done at once.
 for (size_t i = initial_lowered_function_count; i < result_module.functions().size(); i++) {
 // Note that lower_parallel_tasks() appends to the end of closure_implementations
 result_module.functions()[i].body =
 lower_parallel_tasks(result_module.functions()[i].body, closure_implementations,
 result_module.functions()[i].name, t);
 }
 for (auto &lowered_func : closure_implementations) {
 result_module.append(lowered_func);
 }
 debug(2) << "Lowering after generating parallel tasks and closures:\n"
 << s << "\n\n";

 vector<Argument> public_args = args;
 for (const auto &out : outputs) {
 for (const Parameter &buf : out.output_buffers()) {
 public_args.emplace_back(buf.name(),
 Argument::OutputBuffer,
 buf.type(), buf.dimensions(), buf.get_argument_estimates());
 }
 }

 for (const InferredArgument &arg : inferred_args) {
 if (arg.param.defined() && arg.param.name() == "__user_context") {
 // The user context is always in the inferred args, but is
 // not required to be in the args list.
 continue;
 }

 internal_assert(arg.arg.is_input()) << "Expected only input Arguments here";

 bool found = false;
 for (const Argument &a : args) {
 found |= (a.name == arg.arg.name);
 }

 if (arg.buffer.defined() && !found) {
 // It's a raw Buffer used that isn't in the args
 // list. Embed it in the output instead.
 debug(1) << "Embedding image " << arg.buffer.name() << "\n";
 result_module.append(arg.buffer);
 } else if (!found) {
 std::ostringstream err;
 err << "Generated code refers to ";
 if (arg.arg.is_buffer()) {
 err << "image ";
 }
 err << "parameter " << arg.arg.name
 << ", which was not found in the argument list.\n";

 err << "\nArgument list specified: ";
 for (const auto &arg : args) {
 err << arg.name << " ";
 }
 err << "\n\nParameters referenced in generated code: ";
 for (const InferredArgument &ia : inferred_args) {
 if (ia.arg.name != "__user_context") {
 err << ia.arg.name << " ";
 }
 }
 err << "\n\n";
 user_error << err.str();
 }
 }

 // We're about to drop the environment and outputs vector, which
 // contain the only strong refs to Functions that may still be
 // pointed to by the IR. So make those refs strong.
 class StrengthenRefs : public IRMutator {
 using IRMutator::visit;
 Expr visit(const Call *c) override {
 Expr expr = IRMutator::visit(c);
 c = expr.as<Call>();
 internal_assert(c);
 if (c->func.defined()) {
 FunctionPtr ptr = c->func;
 ptr.strengthen();
 expr = Call::make(c->type, c->name, c->args, c->call_type,
 ptr, c->value_index,
 c->image, c->param);
 }
 return expr;
 }
 };
 s = StrengthenRefs().mutate(s);

 LoweredFunc main_func(pipeline_name, public_args, s, linkage_type);

 // If we're in debug mode, add code that prints the args.
 if (t.has_feature(Target::Debug)) {
 debug_arguments(&main_func, t);
 }

 result_module.append(main_func);

 auto *logger = get_compiler_logger();
 if (logger) {
 auto time_end = std::chrono::high_resolution_clock::now();
 std::chrono::duration<double> diff = time_end - time_start;
 logger->record_compilation_time(CompilerLogger::Phase::HalideLowering, diff.count());
 }
}

} // namespace

Module lower(const vector<Function> &output_funcs,
 const string &pipeline_name,
 const Target &t,
 const vector<Argument> &args,
 const LinkageType linkage_type,
 const vector<Stmt> &requirements,
 bool trace_pipeline,
 const vector<IRMutator *> &custom_passes) {
 Module result_module{strip_namespaces(pipeline_name), t};
 run_with_large_stack([&]() {
 lower_impl(output_funcs, pipeline_name, t, args, linkage_type, requirements, trace_pipeline, custom_passes, result_module);
 });
 return result_module;
}

Stmt lower_main_stmt(const std::vector<Function> &output_funcs,
 const std::string &pipeline_name,
 const Target &t,
 const std::vector<Stmt> &requirements,
 bool trace_pipeline,
 const std::vector<IRMutator *> &custom_passes) {
 // We really ought to start applying for appellation d'origine contrôlée
 // status on types representing arguments in the Halide compiler.
 vector<InferredArgument> inferred_args = infer_arguments(Stmt(), output_funcs);
 vector<Argument> args;
 for (const auto &ia : inferred_args) {
 if (!ia.arg.name.empty() && ia.arg.is_input()) {
 args.push_back(ia.arg);
 }
 }

 Module module = lower(output_funcs, pipeline_name, t, args, LinkageType::External, requirements, trace_pipeline, custom_passes);

 return module.functions().front().body;
}

} // namespace Internal
} // namespace Halide