Commit 3df2f356eba9b0882ee3fa09704aae7dc173f3d4 | zig

author	Matthew Lugg <mlugg@mlugg.co.uk> 2023-04-26 01:43:55+01:00
committer	Matthew Lugg <mlugg@mlugg.co.uk> 2023-04-26 01:46:09+01:00
log	3df2f356eba9b0882ee3fa09704aae7dc173f3d4
tree	8148aa73bb87733ef5c221c0ebf60a9c07cfd657
parent	2e23ddbe7ba48857fbdcf014da3251f1decca00d
signature	Commit is signed but in an unrecognized format.

Sema: avoid emitting sequential dbg_stmt instructions

Often, a `dbg_stmt` ends up being associated with no real code because
whatever it referred to was eliminated by semantic analysis. In these
cases, Sema can replace the last `dbg_stmt` with the new one to avoid
redundant AIR instructions which at best are nops and at worst cause
backends to emit useless info (e.g. CBE does this).

1 files changed, 13 insertions(+), 0 deletions(-)

src
- Sema.zig

src/Sema.zig+13

...	@@ -5852,6 +5852,19 @@ fn zirDbgStmt(sema: Sema, block: Block, inst: Zir.Inst.Index) CompileError!voi	...	@@ -5852,6 +5852,19 @@ fn zirDbgStmt(sema: Sema, block: Block, inst: Zir.Inst.Index) CompileError!voi
5852	if (block.is_comptime or sema.mod.comp.bin_file.options.strip) return;	5852	if (block.is_comptime or sema.mod.comp.bin_file.options.strip) return;
5853		5853
5854	const inst_data = sema.code.instructions.items(.data)[inst].dbg_stmt;	5854	const inst_data = sema.code.instructions.items(.data)[inst].dbg_stmt;
		5855
		5856	if (block.instructions.items.len != 0) {
		5857	const idx = block.instructions.items[block.instructions.items.len - 1];
		5858	if (sema.air_instructions.items(.tag)[idx] == .dbg_stmt) {
		5859	// The previous dbg_stmt didn't correspond to any actual code, so replace it.
		5860	sema.air_instructions.items(.data)[idx].dbg_stmt = .{
		5861	.line = inst_data.line,
		5862	.column = inst_data.column,
		5863	};
		5864	return;
		5865	}
		5866	}
		5867
5855	_ = try block.addInst(.{	5868	_ = try block.addInst(.{
5856	.tag = .dbg_stmt,	5869	.tag = .dbg_stmt,
5857	.data = .{ .dbg_stmt = .{	5870	.data = .{ .dbg_stmt = .{