code coverage dumping tool basic implementation

* std.debug.Dwarf: add `sortCompileUnits` along with a field to track
  the state for the purpose of assertions and correct API usage.
  This makes batch lookups faster.
  - in the future, findCompileUnit should be enhanced to rely on sorted
    compile units as well.
* implement `std.debug.Dwarf.resolveSourceLocations` as well as
  `std.debug.Info.resolveSourceLocations`. It's still pretty slow, since
  it calls getLineNumberInfo for each array element, repeating a lot of
  work unnecessarily.
* integrate these APIs with `std.Progress` to understand what is taking
  so long.

The output I'm seeing from this tool shows a lot of missing source
locations. In particular, the main area of interest is missing for my
tokenizer fuzzing example.

1 files changed, 10 insertions, 7 deletions

diff --git a/lib/std/debug/Info.zig b/lib/std/debug/Info.zig
index 5276ba68ec..3c61c4072f 100644
--- a/lib/std/debug/Info.zig
+++ b/lib/std/debug/Info.zig
@@ -20,9 +20,14 @@ address_map: std.AutoArrayHashMapUnmanaged(u64, Dwarf.ElfModule),
 
 pub const LoadError = Dwarf.ElfModule.LoadError;
 
-pub fn load(gpa: Allocator, path: Path) LoadError!Info {
+pub fn load(gpa: Allocator, path: Path, parent_prog_node: std.Progress.Node) LoadError!Info {
     var sections: Dwarf.SectionArray = Dwarf.null_section_array;
-    const elf_module = try Dwarf.ElfModule.loadPath(gpa, path, null, null, &sections, null);
+    var prog_node = parent_prog_node.start("Loading Debug Info", 0);
+    defer prog_node.end();
+    var elf_module = try Dwarf.ElfModule.loadPath(gpa, path, null, null, &sections, null);
+    prog_node.end();
+    prog_node = parent_prog_node.start("Sort Compile Units", 0);
+    try elf_module.dwarf.sortCompileUnits();
     var info: Info = .{
         .address_map = .{},
     };
@@ -38,10 +43,7 @@ pub fn deinit(info: *Info, gpa: Allocator) void {
     info.* = undefined;
 }
 
-pub const ResolveSourceLocationsError = error{
-    MissingDebugInfo,
-    InvalidDebugInfo,
-} || Allocator.Error;
+pub const ResolveSourceLocationsError = Dwarf.ResolveSourceLocationsError;
 
 pub fn resolveSourceLocations(
     info: *Info,
@@ -49,9 +51,10 @@ pub fn resolveSourceLocations(
     sorted_pc_addrs: []const u64,
     /// Asserts its length equals length of `sorted_pc_addrs`.
     output: []std.debug.SourceLocation,
+    parent_prog_node: std.Progress.Node,
 ) ResolveSourceLocationsError!void {
     assert(sorted_pc_addrs.len == output.len);
     if (info.address_map.entries.len != 1) @panic("TODO");
     const elf_module = &info.address_map.values()[0];
-    return elf_module.dwarf.resolveSourceLocations(gpa, sorted_pc_addrs, output);
+    return elf_module.dwarf.resolveSourceLocations(gpa, sorted_pc_addrs, output, parent_prog_node);
 }