Merge pull request #15257 from Luukdegram/wasm-tagname

wasm: Implement `@tagName` instruction

2 files changed, 56 insertions, 2 deletions

diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig
index b1fc25bf26..2125a8faaa 100644
--- a/src/link/Wasm.zig
+++ b/src/link/Wasm.zig
@@ -30,6 +30,7 @@ const Symbol = @import("Wasm/Symbol.zig");
 const Object = @import("Wasm/Object.zig");
 const Archive = @import("Wasm/Archive.zig");
 const types = @import("Wasm/types.zig");
+pub const Relocation = types.Relocation;
 
 pub const base_tag: link.File.Tag = .wasm;
 
@@ -178,6 +179,10 @@ debug_str_atom: ?Atom.Index = null,
 debug_pubnames_atom: ?Atom.Index = null,
 debug_pubtypes_atom: ?Atom.Index = null,
 
+/// List of atom indexes of functions that are generated by the backend,
+/// rather than by the linker.
+synthetic_functions: std.ArrayListUnmanaged(Atom.Index) = .{},
+
 pub const Segment = struct {
     alignment: u32,
     size: u32,
@@ -1208,7 +1213,7 @@ fn resolveLazySymbols(wasm: *Wasm) !void {
 
 // Tries to find a global symbol by its name. Returns null when not found,
 /// and its location when it is found.
-fn findGlobalSymbol(wasm: *Wasm, name: []const u8) ?SymbolLoc {
+pub fn findGlobalSymbol(wasm: *Wasm, name: []const u8) ?SymbolLoc {
     const offset = wasm.string_table.getOffset(name) orelse return null;
     return wasm.globals.get(offset);
 }
@@ -1287,6 +1292,7 @@ pub fn deinit(wasm: *Wasm) void {
     wasm.exports.deinit(gpa);
 
     wasm.string_table.deinit(gpa);
+    wasm.synthetic_functions.deinit(gpa);
 
     if (wasm.dwarf) |*dwarf| {
         dwarf.deinit();
@@ -2272,6 +2278,49 @@ fn createSyntheticFunction(
     atom.offset = prev_atom.offset + prev_atom.size;
 }
 
+/// Unlike `createSyntheticFunction` this function is to be called by
+/// the codegeneration backend. This will not allocate the created Atom yet,
+/// but will instead be appended to `synthetic_functions` list and will be
+/// parsed at the end of code generation.
+/// Returns the index of the symbol.
+pub fn createFunction(
+    wasm: *Wasm,
+    symbol_name: []const u8,
+    func_ty: std.wasm.Type,
+    function_body: *std.ArrayList(u8),
+    relocations: *std.ArrayList(Relocation),
+) !u32 {
+    const loc = try wasm.createSyntheticSymbol(symbol_name, .function);
+
+    const atom_index = @intCast(Atom.Index, wasm.managed_atoms.items.len);
+    const atom = try wasm.managed_atoms.addOne(wasm.base.allocator);
+    atom.* = .{
+        .size = @intCast(u32, function_body.items.len),
+        .offset = 0,
+        .sym_index = loc.index,
+        .file = null,
+        .alignment = 1,
+        .next = null,
+        .prev = null,
+        .code = function_body.moveToUnmanaged(),
+        .relocs = relocations.moveToUnmanaged(),
+    };
+    const symbol = loc.getSymbol(wasm);
+    symbol.setFlag(.WASM_SYM_VISIBILITY_HIDDEN); // ensure function does not get exported
+
+    const section_index = wasm.code_section_index orelse idx: {
+        const index = @intCast(u32, wasm.segments.items.len);
+        try wasm.appendDummySegment();
+        break :idx index;
+    };
+    try wasm.appendAtomAtIndex(section_index, atom_index);
+    try wasm.symbol_atom.putNoClobber(wasm.base.allocator, loc, atom_index);
+    try wasm.atom_types.put(wasm.base.allocator, atom_index, try wasm.putOrGetFuncType(func_ty));
+    try wasm.synthetic_functions.append(wasm.base.allocator, atom_index);
+
+    return loc.index;
+}
+
 fn initializeTLSFunction(wasm: *Wasm) !void {
     if (!wasm.base.options.shared_memory) return;
 
@@ -3306,6 +3355,11 @@ pub fn flushModule(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod
             }
         }
 
+        // also parse any backend-generated functions
+        for (wasm.synthetic_functions.items) |atom_index| {
+            try wasm.parseAtom(atom_index, .function);
+        }
+
         if (wasm.dwarf) |*dwarf| {
             try dwarf.flushModule(wasm.base.options.module.?);
         }
diff --git a/src/link/Wasm/Atom.zig b/src/link/Wasm/Atom.zig
index 7d2f5a6696..f8092c6db1 100644
--- a/src/link/Wasm/Atom.zig
+++ b/src/link/Wasm/Atom.zig
@@ -43,7 +43,7 @@ pub const Index = u32;
 
 /// Represents a default empty wasm `Atom`
 pub const empty: Atom = .{
-    .alignment = 0,
+    .alignment = 1,
     .file = null,
     .next = null,
     .offset = 0,