Closure.h
#ifndef HALIDE_CLOSURE_H
#define HALIDE_CLOSURE_H
/** \file
*
* Provides Closure class.
*/
#include <map>
#include <string>
#include "Buffer.h"
#include "IR.h"
#include "IRVisitor.h"
#include "Scope.h"
namespace Halide {
namespace Internal {
/** A helper class to manage closures. Walks over a statement and
* retrieves all the references within it to external symbols
* (variables and allocations). It then helps you build a struct
* containing the current values of these symbols that you can use as
* a closure if you want to migrate the body of the statement to its
* own function (e.g. because it's the body of a parallel for loop. */
class Closure : public IRVisitor {
protected:
Scope<> ignore;
using IRVisitor::visit;
void visit(const Let *op) override;
void visit(const LetStmt *op) override;
void visit(const For *op) override;
void visit(const Load *op) override;
void visit(const Store *op) override;
void visit(const Allocate *op) override;
void visit(const Variable *op) override;
void visit(const Atomic *op) override;
public:
/** Information about a buffer reference from a closure. */
struct Buffer {
/** The type of the buffer referenced. */
Type type;
/** The dimensionality of the buffer. */
uint8_t dimensions = 0;
/** The buffer is read from. */
bool read = false;
/** The buffer is written to. */
bool write = false;
/** The buffer is a texture */
MemoryType memory_type = MemoryType::Auto;
/** The size of the buffer if known, otherwise zero. */
size_t size = 0;
Buffer() = default;
};
protected:
void found_buffer_ref(const std::string &name, Type type,
bool read, bool written, const Halide::Buffer<> &image);
public:
Closure() = default;
// Movable but not copyable.
Closure(const Closure &) = delete;
Closure &operator=(const Closure &) = delete;
Closure(Closure &&) = default;
Closure &operator=(Closure &&) = default;
/** Traverse a statement and find all references to external
* symbols.
*
* When the closure encounters a read or write to 'foo', it
* assumes that the host pointer is found in the symbol table as
* 'foo.host', and any halide_buffer_t pointer is found under
* 'foo.buffer'.
*
* Calling this multiple times (on multiple statements) is legal
* (and will produce a unified closure).
**/
void include(const Stmt &s, const std::string &loop_variable = "");
/** External variables referenced. There's code that assumes iterating over
* this repeatedly gives a consistent order, so don't swap out the data type
* for something non-deterministic. */
std::map<std::string, Type> vars;
/** External allocations referenced. */
std::map<std::string, Buffer> buffers;
/** Pack a closure into a struct. */
Expr pack_into_struct() const;
/** Unpack a closure around a Stmt, putting all the names in scope. */
Stmt unpack_from_struct(const Expr &, const Stmt &) const;
};
} // namespace Internal
} // namespace Halide
#endif