Commit 91570cc42d4fe973d15ac05cdecff42051f154ad | zig

author	Adam Goertz <adambgoertz@gmail.com> 2023-11-04 23:00:28+00:00
committer	Adam Goertz <adambgoertz@gmail.com> 2023-11-06 04:31:55+00:00
log	91570cc42d4fe973d15ac05cdecff42051f154ad
tree	933200ee149c2557d3739ed7332e59b4e7ca341e
parent	1b0b46a8a9f5ed3ebaf35e3018fd5402957552ae

zig-reduce: Reduce `if` expressions

Perform these transformations in this priority order:
1. If the `else` expression is missing or an empty block, replace the condition with `if (true)` if it is not already.
2. If the `then` block is empty, replace the condition with `if (false)` if it is not already.
3. If the condition is `if (true)`, replace the `if` expression with the contents of the `then` expression.
4. If the condition is `if (false)`, replace the `if` expression with the contents of the `else` expression.

3 files changed, 85 insertions(+), 13 deletions(-)

lib
- std
  - zig
    render.zig
src
- reduce.zig
- reduce
  - Walk.zig

lib/std/zig/render.zig+12-5

...	...	@@ -25,7 +25,9 @@ pub const Fixups = struct {
25	25	/// These global declarations will be omitted.
26	26	omit_nodes: std.AutoHashMapUnmanaged(Ast.Node.Index, void) = .{},
27	27	/// These expressions will be replaced with the string value.
28		replace_nodes: std.AutoHashMapUnmanaged(Ast.Node.Index, []const u8) = .{},
	28	replace_nodes_with_string: std.AutoHashMapUnmanaged(Ast.Node.Index, []const u8) = .{},
	29	/// These nodes will be replaced with a different node.
	30	replace_nodes_with_node: std.AutoHashMapUnmanaged(Ast.Node.Index, Ast.Node.Index) = .{},
29	31	/// Change all identifier names matching the key to be value instead.
30	32	rename_identifiers: std.StringArrayHashMapUnmanaged([]const u8) = .{},
31	33
...	...	@@ -37,7 +39,8 @@ pub const Fixups = struct {
37	39	return f.unused_var_decls.count() +
38	40	f.gut_functions.count() +
39	41	f.omit_nodes.count() +
40		f.replace_nodes.count() +
	42	f.replace_nodes_with_string.count() +
	43	f.replace_nodes_with_node.count() +
41	44	f.rename_identifiers.count() +
42	45	@intFromBool(f.rebase_imported_paths != null);
43	46	}
...	...	@@ -46,7 +49,8 @@ pub const Fixups = struct {
46	49	f.unused_var_decls.clearRetainingCapacity();
47	50	f.gut_functions.clearRetainingCapacity();
48	51	f.omit_nodes.clearRetainingCapacity();
49		f.replace_nodes.clearRetainingCapacity();
	52	f.replace_nodes_with_string.clearRetainingCapacity();
	53	f.replace_nodes_with_node.clearRetainingCapacity();
50	54	f.rename_identifiers.clearRetainingCapacity();
51	55
52	56	f.rebase_imported_paths = null;
...	...	@@ -56,7 +60,8 @@ pub const Fixups = struct {
56	60	f.unused_var_decls.deinit(gpa);
57	61	f.gut_functions.deinit(gpa);
58	62	f.omit_nodes.deinit(gpa);
59		f.replace_nodes.deinit(gpa);
	63	f.replace_nodes_with_string.deinit(gpa);
	64	f.replace_nodes_with_node.deinit(gpa);
60	65	f.rename_identifiers.deinit(gpa);
61	66	f.* = undefined;
62	67	}
...	...	@@ -329,10 +334,12 @@ fn renderExpression(r: *Render, node: Ast.Node.Index, space: Space) Error!void {
329	334	const main_tokens = tree.nodes.items(.main_token);
330	335	const node_tags = tree.nodes.items(.tag);
331	336	const datas = tree.nodes.items(.data);
332		if (r.fixups.replace_nodes.get(node)) \|replacement\| {
	337	if (r.fixups.replace_nodes_with_string.get(node)) \|replacement\| {
333	338	try ais.writer().writeAll(replacement);
334	339	try renderOnlySpace(r, space);
335	340	return;
	341	} else if (r.fixups.replace_nodes_with_node.get(node)) \|replacement\| {
	342	return renderExpression(r, replacement, space);
336	343	}
337	344	switch (node_tags[node]) {
338	345	.identifier => {

src/reduce.zig+13-4

...	...	@@ -226,7 +226,7 @@ pub fn main(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
226	226	}
227	227
228	228	try std.fs.cwd().writeFile(root_source_file_path, rendered.items);
229		//std.debug.print("trying this code:\n{s}\n", .{rendered.items});
	229	// std.debug.print("trying this code:\n{s}\n", .{rendered.items});
230	230
231	231	const interestingness = try runCheck(arena, interestingness_argv.items);
232	232	std.debug.print("{d} random transformations: {s}. {d}/{d}\n", .{
...	...	@@ -324,11 +324,20 @@ fn transformationsToFixups(
324	324	.delete_var_decl => \|delete_var_decl\| {
325	325	try fixups.omit_nodes.put(gpa, delete_var_decl.var_decl_node, {});
326	326	for (delete_var_decl.references.items) \|ident_node\| {
327		try fixups.replace_nodes.put(gpa, ident_node, "undefined");
	327	try fixups.replace_nodes_with_string.put(gpa, ident_node, "undefined");
328	328	}
329	329	},
330	330	.replace_with_undef => \|node\| {
331		try fixups.replace_nodes.put(gpa, node, "undefined");
	331	try fixups.replace_nodes_with_string.put(gpa, node, "undefined");
	332	},
	333	.replace_with_true => \|node\| {
	334	try fixups.replace_nodes_with_string.put(gpa, node, "true");
	335	},
	336	.replace_with_false => \|node\| {
	337	try fixups.replace_nodes_with_string.put(gpa, node, "false");
	338	},
	339	.replace_node => \|r\| {
	340	try fixups.replace_nodes_with_node.put(gpa, r.to_replace, r.replacement);
332	341	},
333	342	.inline_imported_file => \|inline_imported_file\| {
334	343	const full_imported_path = try std.fs.path.join(gpa, &.{
...	...	@@ -371,7 +380,7 @@ fn transformationsToFixups(
371	380	try other_file_ast.renderToArrayList(&other_source, inlined_fixups);
372	381	try other_source.appendSlice("}");
373	382
374		try fixups.replace_nodes.put(
	383	try fixups.replace_nodes_with_string.put(
375	384	gpa,
376	385	inline_imported_file.builtin_call_node,
377	386	try arena.dupe(u8, other_source.items),

src/reduce/Walk.zig+60-4

...	...	@@ -27,6 +27,15 @@ pub const Transformation = union(enum) {
27	27	},
28	28	/// Replace an expression with `undefined`.
29	29	replace_with_undef: Ast.Node.Index,
	30	/// Replace an expression with `true`.
	31	replace_with_true: Ast.Node.Index,
	32	/// Replace an expression with `false`.
	33	replace_with_false: Ast.Node.Index,
	34	/// Replace a node with another node.
	35	replace_node: struct {
	36	to_replace: Ast.Node.Index,
	37	replacement: Ast.Node.Index,
	38	},
30	39	/// Replace an `@import` with the imported file contents wrapped in a struct.
31	40	inline_imported_file: InlineImportedFile,
32	41
...	...	@@ -558,7 +567,7 @@ fn walkExpression(w: *Walk, node: Ast.Node.Index) Error!void {
558	567
559	568	.if_simple,
560	569	.@"if",
561		=> return walkIf(w, ast.fullIf(node).?),
	570	=> return walkIf(w, node, ast.fullIf(node).?),
562	571
563	572	.asm_simple,
564	573	.@"asm",
...	...	@@ -861,8 +870,6 @@ fn walkWhile(w: *Walk, while_node: Ast.full.While) Error!void {
861	870	try walkExpression(w, while_node.ast.cont_expr);
862	871	}
863	872
864		try walkExpression(w, while_node.ast.cond_expr); // condition
865
866	873	if (while_node.ast.then_expr != 0) {
867	874	try walkExpression(w, while_node.ast.then_expr);
868	875	}
...	...	@@ -881,7 +888,37 @@ fn walkFor(w: *Walk, for_node: Ast.full.For) Error!void {
881	888	}
882	889	}
883	890
884		fn walkIf(w: *Walk, if_node: Ast.full.If) Error!void {
	891	fn walkIf(w: *Walk, node_index: Ast.Node.Index, if_node: Ast.full.If) Error!void {
	892	assert(if_node.ast.cond_expr != 0);
	893	assert(if_node.ast.then_expr != 0);
	894
	895	// Perform these transformations in this priority order:
	896	// 1. If the `else` expression is missing or an empty block, replace the condition with `if (true)` if it is not already.
	897	// 2. If the `then` block is empty, replace the condition with `if (false)` if it is not already.
	898	// 3. If the condition is `if (true)`, replace the `if` expression with the contents of the `then` expression.
	899	// 4. If the condition is `if (false)`, replace the `if` expression with the contents of the `else` expression.
	900	if (!isTrueIdent(w.ast, if_node.ast.cond_expr) and
	901	(if_node.ast.else_expr == 0 or isEmptyBlock(w.ast, if_node.ast.else_expr)))
	902	{
	903	try w.transformations.ensureUnusedCapacity(1);
	904	w.transformations.appendAssumeCapacity(.{ .replace_with_true = if_node.ast.cond_expr });
	905	} else if (!isFalseIdent(w.ast, if_node.ast.cond_expr) and isEmptyBlock(w.ast, if_node.ast.then_expr)) {
	906	try w.transformations.ensureUnusedCapacity(1);
	907	w.transformations.appendAssumeCapacity(.{ .replace_with_false = if_node.ast.cond_expr });
	908	} else if (isTrueIdent(w.ast, if_node.ast.cond_expr)) {
	909	try w.transformations.ensureUnusedCapacity(1);
	910	w.transformations.appendAssumeCapacity(.{ .replace_node = .{
	911	.to_replace = node_index,
	912	.replacement = if_node.ast.then_expr,
	913	} });
	914	} else if (isFalseIdent(w.ast, if_node.ast.cond_expr)) {
	915	try w.transformations.ensureUnusedCapacity(1);
	916	w.transformations.appendAssumeCapacity(.{ .replace_node = .{
	917	.to_replace = node_index,
	918	.replacement = if_node.ast.else_expr,
	919	} });
	920	}
	921
885	922	try walkExpression(w, if_node.ast.cond_expr); // condition
886	923
887	924	if (if_node.ast.then_expr != 0) {
...	...	@@ -1002,6 +1039,14 @@ fn isUndefinedIdent(ast: *const Ast, node: Ast.Node.Index) bool {
1002	1039	return isMatchingIdent(ast, node, "undefined");
1003	1040	}
1004	1041
	1042	fn isTrueIdent(ast: *const Ast, node: Ast.Node.Index) bool {
	1043	return isMatchingIdent(ast, node, "true");
	1044	}
	1045
	1046	fn isFalseIdent(ast: *const Ast, node: Ast.Node.Index) bool {
	1047	return isMatchingIdent(ast, node, "false");
	1048	}
	1049
1005	1050	fn isMatchingIdent(ast: *const Ast, node: Ast.Node.Index, string: []const u8) bool {
1006	1051	const node_tags = ast.nodes.items(.tag);
1007	1052	const main_tokens = ast.nodes.items(.main_token);
...	...	@@ -1014,3 +1059,14 @@ fn isMatchingIdent(ast: *const Ast, node: Ast.Node.Index, string: []const u8) bo
1014	1059	else => return false,
1015	1060	}
1016	1061	}
	1062
	1063	fn isEmptyBlock(ast: *const Ast, node: Ast.Node.Index) bool {
	1064	const node_tags = ast.nodes.items(.tag);
	1065	const node_data = ast.nodes.items(.data);
	1066	switch (node_tags[node]) {
	1067	.block_two => {
	1068	return node_data[node].lhs == 0 and node_data[node].rhs == 0;
	1069	},
	1070	else => return false,
	1071	}
	1072	}