Commit `31a7f22b80`

mlugg <mlugg@mlugg.co.uk>

2024-03-25 04:51:58

llvm: update current debug location scope when entering debug scope

This issue was causing debug information to sometimes not function correctly for some local variables, with debuggers simply reporting that the variable does not exist. What was happening was that after an AIR body - and thus debug lexical scope - begins, but before any `dbg_stmt` within it, the `scope` on `self.wip.debug_location` refers to the parent scope, but the `scope` field on the `DILocalVariable` metadata passed to `@llvm.dbg.declare` points, correctly, to the nested scope. I haven't looked into precisely what happens here, but in short, it would appear that LLVM Doesn't Like It (tm). The fix is simple: when we change `self.scope` at the start or end of an AIR body, also modify the scope on `self.wip.debug_location`. This is correct as we always want the debug info for an instruction to be associated with the block it is within, even if the line/column are slightly outdated for any reason.

master

1 parent 5c62831

Changed files (1)

src

codegen

llvm.zig

@@ -5202,6 +5202,16 @@ pub const FuncGen = struct {
             self.prev_dbg_line,
             self.prev_dbg_column,
         );
+
+        switch (self.wip.debug_location) {
+            .location => |*l| l.scope = self.scope,
+            .no_location => {},
+        }
+        defer switch (self.wip.debug_location) {
+            .location => |*l| l.scope = old_scope,
+            .no_location => {},
+        };
+
         try self.genBody(body);
     }

Commit 31a7f22b80

Commit `31a7f22b80`