| 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
src/Sema.zig+13
| ... | ... | @@ -5852,6 +5852,19 @@ fn zirDbgStmt(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!voi |
| 5852 | 5852 | if (block.is_comptime or sema.mod.comp.bin_file.options.strip) return; |
| 5853 | 5853 | |
| 5854 | 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 | 5868 | _ = try block.addInst(.{ |
| 5856 | 5869 | .tag = .dbg_stmt, |
| 5857 | 5870 | .data = .{ .dbg_stmt = .{ |