wasm-linker: support incremental debug info

Although the wasm-linker previously already supported
debug information in incremental-mode, this was no longer
working as-is with the addition of supporting object-file-parsed
debug information. This commit implements the Zig-created debug information
structure from scratch which is a lot more robust and also allows
being linked with debug information from other object files.

1 files changed, 27 insertions, 46 deletions

diff --git a/src/link/Dwarf.zig b/src/link/Dwarf.zig
index 671425ab71..474c822ae6 100644
--- a/src/link/Dwarf.zig
+++ b/src/link/Dwarf.zig
@@ -861,9 +861,7 @@ pub fn commitDeclState(
                             },
                             .wasm => {
                                 const wasm_file = file.cast(File.Wasm).?;
-                                const segment_index = wasm_file.debug_line_index.?;
-                                const atom = wasm_file.atoms.get(segment_index).?;
-                                const debug_line = atom.getFirstZigAtom().code;
+                                const debug_line = wasm_file.debug_line_atom.?.code;
                                 writeDbgLineNopsBuffered(debug_line.items, src_fn.off, 0, &.{}, src_fn.len);
                             },
                             else => unreachable,
@@ -975,24 +973,21 @@ pub fn commitDeclState(
                 },
                 .wasm => {
                     const wasm_file = file.cast(File.Wasm).?;
-                    const segment_index = wasm_file.debug_line_index.?;
-                    const segment = &wasm_file.segments.items[segment_index];
-                    const atom = wasm_file.atoms.get(segment_index).?;
-                    const debug_line = &atom.getFirstZigAtom().code;
-                    if (needed_size != segment.size) {
+                    const atom = wasm_file.debug_line_atom.?;
+                    const debug_line = &atom.code;
+                    const segment_size = debug_line.items.len;
+                    if (needed_size != segment_size) {
                         log.debug(" needed size does not equal allocated size: {d}", .{needed_size});
-                        if (needed_size > segment.size) {
-                            log.debug("  allocating {d} bytes for 'debug line' information", .{needed_size - segment.size});
+                        if (needed_size > segment_size) {
+                            log.debug("  allocating {d} bytes for 'debug line' information", .{needed_size - segment_size});
                             try debug_line.resize(self.allocator, needed_size);
-                            mem.set(u8, debug_line.items[segment.size..], 0);
+                            mem.set(u8, debug_line.items[segment_size..], 0);
                         }
-                        segment.size = needed_size;
                         debug_line.items.len = needed_size;
                     }
-                    const offset = segment.offset + src_fn.off;
                     writeDbgLineNopsBuffered(
                         debug_line.items,
-                        offset,
+                        src_fn.off,
                         prev_padding_size,
                         dbg_line_buffer.items,
                         next_padding_size,
@@ -1150,12 +1145,8 @@ fn updateDeclDebugInfoAllocation(self: *Dwarf, file: *File, atom: *Atom, len: u3
                     },
                     .wasm => {
                         const wasm_file = file.cast(File.Wasm).?;
-                        const segment_index = wasm_file.debug_info_index.?;
-                        const segment = &wasm_file.segments.items[segment_index];
-                        const info_atom = wasm_file.atoms.get(segment_index).?;
-                        const debug_info = &info_atom.getFirstZigAtom().code;
-                        const offset = segment.offset + atom.off;
-                        try writeDbgInfoNopsToArrayList(gpa, debug_info, offset, 0, &.{0}, atom.len, false);
+                        const debug_info = &wasm_file.debug_info_atom.?.code;
+                        try writeDbgInfoNopsToArrayList(gpa, debug_info, atom.off, 0, &.{0}, atom.len, false);
                     },
                     else => unreachable,
                 }
@@ -1282,28 +1273,25 @@ fn writeDeclDebugInfo(self: *Dwarf, file: *File, atom: *Atom, dbg_info_buf: []co
         },
         .wasm => {
             const wasm_file = file.cast(File.Wasm).?;
-            const segment_index = wasm_file.debug_info_index.?;
-            const segment = &wasm_file.segments.items[segment_index];
-            const info_atom = wasm_file.atoms.get(segment_index).?;
-            const debug_info = &info_atom.getFirstZigAtom().code;
-            if (needed_size != segment.size) {
+            const info_atom = wasm_file.debug_info_atom.?;
+            const debug_info = &info_atom.code;
+            const segment_size = debug_info.items.len;
+            if (needed_size != segment_size) {
                 log.debug(" needed size does not equal allocated size: {d}", .{needed_size});
-                if (needed_size > segment.size) {
-                    log.debug("  allocating {d} bytes for 'debug info' information", .{needed_size - segment.size});
+                if (needed_size > segment_size) {
+                    log.debug("  allocating {d} bytes for 'debug info' information", .{needed_size - segment_size});
                     try debug_info.resize(self.allocator, needed_size);
-                    mem.set(u8, debug_info.items[segment.size..], 0);
+                    mem.set(u8, debug_info.items[segment_size..], 0);
                 }
-                segment.size = needed_size;
                 debug_info.items.len = needed_size;
             }
-            const offset = segment.offset + atom.off;
             log.debug(" writeDbgInfoNopsToArrayList debug_info_len={d} offset={d} content_len={d} next_padding_size={d}", .{
-                debug_info.items.len, offset, dbg_info_buf.len, next_padding_size,
+                debug_info.items.len, atom.off, dbg_info_buf.len, next_padding_size,
             });
             try writeDbgInfoNopsToArrayList(
                 gpa,
                 debug_info,
-                offset,
+                atom.off,
                 prev_padding_size,
                 dbg_info_buf,
                 next_padding_size,
@@ -1344,10 +1332,8 @@ pub fn updateDeclLineNumber(self: *Dwarf, file: *File, decl: *const Module.Decl)
         },
         .wasm => {
             const wasm_file = file.cast(File.Wasm).?;
-            const segment_index = wasm_file.debug_line_index.?;
-            const segment = wasm_file.segments.items[segment_index];
-            const offset = segment.offset + decl.fn_link.wasm.src_fn.off + self.getRelocDbgLineOff();
-            const atom = wasm_file.atoms.get(segment_index).?.getFirstZigAtom();
+            const offset = decl.fn_link.wasm.src_fn.off + self.getRelocDbgLineOff();
+            const atom = wasm_file.debug_line_atom.?;
             mem.copy(u8, atom.code.items[offset..], &data);
         },
         else => unreachable,
@@ -1584,8 +1570,7 @@ pub fn writeDbgAbbrev(self: *Dwarf, file: *File) !void {
         },
         .wasm => {
             const wasm_file = file.cast(File.Wasm).?;
-            const segment_index = wasm_file.debug_abbrev_index.?;
-            const debug_abbrev = &wasm_file.atoms.get(segment_index).?.getFirstZigAtom().code;
+            const debug_abbrev = &wasm_file.debug_abbrev_atom.?.code;
             try debug_abbrev.resize(wasm_file.base.allocator, needed_size);
             mem.copy(u8, debug_abbrev.items, &abbrev_buf);
         },
@@ -1697,8 +1682,7 @@ pub fn writeDbgInfoHeader(self: *Dwarf, file: *File, module: *Module, low_pc: u6
         },
         .wasm => {
             const wasm_file = file.cast(File.Wasm).?;
-            const segment_index = wasm_file.debug_info_index.?;
-            const debug_info = &wasm_file.atoms.get(segment_index).?.getFirstZigAtom().code;
+            const debug_info = &wasm_file.debug_info_atom.?.code;
             try writeDbgInfoNopsToArrayList(self.allocator, debug_info, 0, 0, di_buf.items, jmp_amt, false);
         },
         else => unreachable,
@@ -2028,8 +2012,7 @@ pub fn writeDbgAranges(self: *Dwarf, file: *File, addr: u64, size: u64) !void {
         },
         .wasm => {
             const wasm_file = file.cast(File.Wasm).?;
-            const segment_index = wasm_file.debug_ranges_index.?;
-            const debug_ranges = &wasm_file.atoms.get(segment_index).?.getFirstZigAtom().code;
+            const debug_ranges = &wasm_file.debug_ranges_atom.?.code;
             try debug_ranges.resize(wasm_file.base.allocator, needed_size);
             mem.copy(u8, debug_ranges.items, di_buf.items);
         },
@@ -2153,8 +2136,7 @@ pub fn writeDbgLineHeader(self: *Dwarf, file: *File, module: *Module) !void {
         },
         .wasm => {
             const wasm_file = file.cast(File.Wasm).?;
-            const segment_index = wasm_file.debug_line_index.?;
-            const debug_line = wasm_file.atoms.get(segment_index).?.getFirstZigAtom().code;
+            const debug_line = wasm_file.debug_line_atom.?.code;
             writeDbgLineNopsBuffered(debug_line.items, 0, 0, di_buf.items, jmp_amt);
         },
         else => unreachable,
@@ -2303,8 +2285,7 @@ pub fn flushModule(self: *Dwarf, file: *File, module: *Module) !void {
                 },
                 .wasm => {
                     const wasm_file = file.cast(File.Wasm).?;
-                    const segment_index = wasm_file.debug_info_index.?;
-                    const debug_info = wasm_file.atoms.get(segment_index).?.getFirstZigAtom().code;
+                    const debug_info = wasm_file.debug_info_atom.?.code;
                     mem.copy(u8, debug_info.items[reloc.atom.off + reloc.offset ..], &buf);
                 },
                 else => unreachable,