Commit f76027220042d965278184088f1f04b6c8430bcb | zig

author	Luuk de Gram <luuk@degram.dev> 2022-05-01 16:34:05+02:00
committer	Luuk de Gram <luuk@degram.dev> 2022-05-09 18:51:46+02:00
log	f76027220042d965278184088f1f04b6c8430bcb
tree	93e00b10ed446fafd785df7f111eb9431de8e6d3
parent	d46cdb539620a2f3647507ffed519908a1c31647

wasm: Debug info for lines + pro/epilogue

Maps lines and columns between wasm bytecode and Zig source code.
While this supports prologue and epilogue information, we need to add
support for performing relocations as the offsets are relative to the code section,
which means we must relocate it according to the atom offset's offset while keeping function count
in mind as well (due to leb128 encoding).

3 files changed, 82 insertions(+), 0 deletions(-)

src
- arch
  - wasm
    CodeGen.zig
    Emit.zig
    Mir.zig

src/arch/wasm/CodeGen.zig+8

...	@@ -882,6 +882,8 @@ fn genFunc(self: *Self) InnerError!void {	...	@@ -882,6 +882,8 @@ fn genFunc(self: *Self) InnerError!void {
882	self.args = cc_result.args;	882	self.args = cc_result.args;
883	self.return_value = cc_result.return_value;	883	self.return_value = cc_result.return_value;
884		884
		885	try self.addTag(.dbg_prologue_end);
		886
885	// Generate MIR for function body	887	// Generate MIR for function body
886	try self.genBody(self.air.getMainBody());	888	try self.genBody(self.air.getMainBody());
887	// In case we have a return value, but the last instruction is a noreturn (such as a while loop)	889	// In case we have a return value, but the last instruction is a noreturn (such as a while loop)
...	@@ -896,6 +898,8 @@ fn genFunc(self: *Self) InnerError!void {	...	@@ -896,6 +898,8 @@ fn genFunc(self: *Self) InnerError!void {
896	// End of function body	898	// End of function body
897	try self.addTag(.end);	899	try self.addTag(.end);
898		900
		901	try self.addTag(.dbg_epilogue_begin);
		902
899	// check if we have to initialize and allocate anything into the stack frame.	903	// check if we have to initialize and allocate anything into the stack frame.
900	// If so, create enough stack space and insert the instructions at the front of the list.	904	// If so, create enough stack space and insert the instructions at the front of the list.
901	if (self.stack_size > 0) {	905	if (self.stack_size > 0) {
...	@@ -942,6 +946,10 @@ fn genFunc(self: *Self) InnerError!void {	...	@@ -942,6 +946,10 @@ fn genFunc(self: *Self) InnerError!void {
942	.code = self.code,	946	.code = self.code,
943	.locals = self.locals.items,	947	.locals = self.locals.items,
944	.decl = self.decl,	948	.decl = self.decl,
		949	.dbg_output = self.debug_output,
		950	.prev_di_line = 0,
		951	.prev_di_column = 0,
		952	.prev_di_offset = 0,
945	};	953	};
946		954
947	emit.emitMir() catch \|err\| switch (err) {	955	emit.emitMir() catch \|err\| switch (err) {

src/arch/wasm/Emit.zig+55

...	@@ -6,6 +6,7 @@ const std = @import("std");	...	@@ -6,6 +6,7 @@ const std = @import("std");
6	const Mir = @import("Mir.zig");	6	const Mir = @import("Mir.zig");
7	const link = @import("../../link.zig");	7	const link = @import("../../link.zig");
8	const Module = @import("../../Module.zig");	8	const Module = @import("../../Module.zig");
		9	const codegen = @import("../../codegen.zig");
9	const leb128 = std.leb;	10	const leb128 = std.leb;
10		11
11	/// Contains our list of instructions	12	/// Contains our list of instructions
...	@@ -22,6 +23,16 @@ locals: []const u8,	...	@@ -22,6 +23,16 @@ locals: []const u8,
22	/// The declaration that code is being generated for.	23	/// The declaration that code is being generated for.
23	decl: *Module.Decl,	24	decl: *Module.Decl,
24		25
		26	// Debug information
		27	/// Holds the debug information for this emission
		28	dbg_output: codegen.DebugInfoOutput,
		29	/// Previous debug info line
		30	prev_di_line: u32,
		31	/// Previous debug info column
		32	prev_di_column: u32,
		33	/// Previous offset relative to code section
		34	prev_di_offset: u32,
		35
25	const InnerError = error{	36	const InnerError = error{
26	OutOfMemory,	37	OutOfMemory,
27	EmitFail,	38	EmitFail,
...	@@ -40,6 +51,10 @@ pub fn emitMir(emit: *Emit) InnerError!void {	...	@@ -40,6 +51,10 @@ pub fn emitMir(emit: *Emit) InnerError!void {
40	.block => try emit.emitBlock(tag, inst),	51	.block => try emit.emitBlock(tag, inst),
41	.loop => try emit.emitBlock(tag, inst),	52	.loop => try emit.emitBlock(tag, inst),
42		53
		54	.dbg_line => try emit.emitDbgLine(inst),
		55	.dbg_epilogue_begin => try emit.emitDbgEpilogueBegin(),
		56	.dbg_prologue_end => try emit.emitDbgPrologueEnd(),
		57
43	// branch instructions	58	// branch instructions
44	.br_if => try emit.emitLabel(tag, inst),	59	.br_if => try emit.emitLabel(tag, inst),
45	.br_table => try emit.emitBrTable(inst),	60	.br_table => try emit.emitBrTable(inst),
...	@@ -419,3 +434,43 @@ fn emitMemFill(emit: *Emit) !void {	...	@@ -419,3 +434,43 @@ fn emitMemFill(emit: *Emit) !void {
419	// For now we will always emit index 0.	434	// For now we will always emit index 0.
420	try leb128.writeULEB128(emit.code.writer(), @as(u32, 0));	435	try leb128.writeULEB128(emit.code.writer(), @as(u32, 0));
421	}	436	}
		437
		438	fn emitDbgLine(emit: *Emit, inst: Mir.Inst.Index) !void {
		439	const extra_index = emit.mir.instructions.items(.data)[inst].payload;
		440	const dbg_line = emit.mir.extraData(Mir.DbgLineColumn, extra_index).data;
		441	try emit.dbgAdvancePCAndLine(dbg_line.line, dbg_line.column);
		442	}
		443
		444	fn dbgAdvancePCAndLine(emit: *Emit, line: u32, column: u32) !void {
		445	if (emit.dbg_output != .dwarf) return;
		446
		447	const dbg_line = &emit.dbg_output.dwarf.dbg_line;
		448	try dbg_line.ensureUnusedCapacity(11);
		449	dbg_line.appendAssumeCapacity(std.dwarf.LNS.advance_pc);
		450	// TODO: This must emit a relocation to calculate the offset relative
		451	// to the code section start.
		452	leb128.writeULEB128(dbg_line.writer(), emit.offset() - emit.prev_di_offset) catch unreachable;
		453	const delta_line = @intCast(i32, line) - @intCast(i32, emit.prev_di_line);
		454	if (delta_line != 0) {
		455	dbg_line.appendAssumeCapacity(std.dwarf.LNS.advance_line);
		456	leb128.writeILEB128(dbg_line.writer(), delta_line) catch unreachable;
		457	}
		458	dbg_line.appendAssumeCapacity(std.dwarf.LNS.copy);
		459	emit.prev_di_line = line;
		460	emit.prev_di_column = column;
		461	emit.prev_di_offset = emit.offset();
		462	}
		463
		464	fn emitDbgPrologueEnd(emit: *Emit) !void {
		465	if (emit.dbg_output != .dwarf) return;
		466
		467	try emit.dbg_output.dwarf.dbg_line.append(std.dwarf.LNS.set_prologue_end);
		468	try emit.dbgAdvancePCAndLine(emit.prev_di_line, emit.prev_di_column);
		469	}
		470
		471	fn emitDbgEpilogueBegin(emit: *Emit) !void {
		472	if (emit.dbg_output != .dwarf) return;
		473
		474	try emit.dbg_output.dwarf.dbg_line.append(std.dwarf.LNS.set_epilogue_begin);
		475	try emit.dbgAdvancePCAndLine(emit.prev_di_line, emit.prev_di_column);
		476	}

src/arch/wasm/Mir.zig+19

...	@@ -47,6 +47,19 @@ pub const Inst = struct {	...	@@ -47,6 +47,19 @@ pub const Inst = struct {
47	///	47	///
48	/// Type of the loop is given in data `block_type`	48	/// Type of the loop is given in data `block_type`
49	loop = 0x03,	49	loop = 0x03,
		50	/// Inserts debug information about the current line and column
		51	/// of the source code
		52	///
		53	/// Uses `payload` of which the payload type is `DbgLineColumn`
		54	dbg_line = 0x06,
		55	/// Emits epilogue begin debug information
		56	///
		57	/// Uses `nop`
		58	dbg_epilogue_begin = 0x07,
		59	/// Emits prologue end debug information
		60	///
		61	/// Uses `nop`
		62	dbg_prologue_end = 0x08,
50	/// Represents the end of a function body or an initialization expression	63	/// Represents the end of a function body or an initialization expression
51	///	64	///
52	/// Payload is `nop`	65	/// Payload is `nop`
...	@@ -645,3 +658,9 @@ pub const Memory = struct {	...	@@ -645,3 +658,9 @@ pub const Memory = struct {
645	pointer: u32,	658	pointer: u32,
646	offset: u32,	659	offset: u32,
647	};	660	};
		661
		662	/// Maps a source line with wasm bytecode
		663	pub const DbgLineColumn = struct {
		664	line: u32,
		665	column: u32,
		666	};