[Refactor] [ir] Move statements from ir.h to statements.h

[xumingkuan]

Related issue = #933

Changes:

• Move all XxxStmt from ir.h to statements.h;
• Move all implementations of frontend statements from ir.cpp to frontend_ir.cpp;
• Remove #include "statements.h" from visitors.h.

Something that may be useful to reduce the compilation time of the Taichi compiler but I don't know how to do:

• We need OffloadedStmt::TaskType in some files (async_utils.h for example). For now, we can only include statements.h, which includes ir.h. statements.h needs ir.h because it needs the implementation of Stmt, which also needs the implementation of IRNode. However, ir.h may become too short if even IRNode is in statements.h. So shall we separate OffloadedStmt::TaskType in a light-weighted file which doesn't need statements.h?

[Click here for the format server]

---

[k-ye]

LGTM!

So shall we separate OffloadedStmt::TaskType in a light-weighted file which doesn't need statements.h

+N on this

[codecov]

Codecov Report

Merging #1898 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1898   +/-   ##
=======================================
  Coverage   43.81%   43.81%           
=======================================
  Files          45       45           
  Lines        6174     6174           
  Branches     1097     1097           
=======================================
  Hits         2705     2705           
  Misses       3300     3300           
  Partials      169      169           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d266c0f...de9f18c. Read the comment docs.

[yuanming-hu]

Awesome!!

So shall we separate OffloadedStmt::TaskType in a light-weighted file which doesn't need statements.h

+N on this

Maybe we can create an ir_fwd.h file that contains all the existing forward declarations

taichi/taichi/ir/ir.h

Lines 20 to 34 in d266c0f

	class IRBuilder;
	class IRNode;
	class Block;
	class Stmt;
	using pStmt = std::unique_ptr<Stmt>;
	class SNode;
	class ScratchPads;
	using ScratchPadOptions = std::vector<std::pair<int, SNode *>>;
	#define PER_STATEMENT(x) class x;
	#include "taichi/inc/statements.inc.h"
	#undef PER_STATEMENT
	IRBuilder &current_ast_builder();

and a new OffloadedTaskType (which used to be OffloadedStmt::TaskType)?

[k-ye]

and a new OffloadedTaskType (which used to be OffloadedStmt::TaskType)?

SGTM! (But i'd suggest to separate OffloadedTaskType from ir_fwd.h... I think it's even fine to have a header just for this type)