codegen: separate getAnonDeclVAddr into lowerAnonDecl and the former

Implement the stub for Elf.

I believe that separating the concerns, namely, having an interface
function that is responsible for signalling the linker to lower
the anon decl only, and a separate function to obtain the decl's
vaddr is preferable since it allows us to handle codegen errors
in a simpler way.

src/codegen.zig

@@ -739,7 +739,6 @@ fn lowerAnonDeclRef(
     debug_output: DebugInfoOutput,
     reloc_info: RelocInfo,
 ) CodeGenError!Result {
-    _ = src_loc;
     _ = debug_output;
     const target = bin_file.options.target;
     const mod = bin_file.options.module.?;
@@ -752,6 +751,12 @@ fn lowerAnonDeclRef(
         return Result.ok;
     }
 
+    const res = try bin_file.lowerAnonDecl(decl_val, src_loc);
+    switch (res) {
+        .ok => {},
+        .fail => |em| return .{ .fail = em },
+    }
+
     const vaddr = try bin_file.getAnonDeclVAddr(decl_val, .{
         .parent_atom_index = reloc_info.parent_atom_index,
         .offset = code.items.len,

src/link.zig

@@ -937,6 +937,22 @@ pub const File = struct {
         }
     }
 
+    pub const LowerResult = @import("codegen.zig").Result;
+
+    pub fn lowerAnonDecl(base: *File, decl_val: InternPool.Index, src_loc: Module.SrcLoc) !LowerResult {
+        if (build_options.only_c) unreachable;
+        switch (base.tag) {
+            .coff => return @fieldParentPtr(Coff, "base", base).lowerAnonDecl(decl_val, src_loc),
+            .elf => return @fieldParentPtr(Elf, "base", base).lowerAnonDecl(decl_val, src_loc),
+            .macho => return @fieldParentPtr(MachO, "base", base).lowerAnonDecl(decl_val, src_loc),
+            .plan9 => return @fieldParentPtr(Plan9, "base", base).lowerAnonDecl(decl_val, src_loc),
+            .c => unreachable,
+            .wasm => return @fieldParentPtr(Wasm, "base", base).lowerAnonDecl(decl_val, src_loc),
+            .spirv => unreachable,
+            .nvptx => unreachable,
+        }
+    }
+
     pub fn getAnonDeclVAddr(base: *File, decl_val: InternPool.Index, reloc_info: RelocInfo) !u64 {
         if (build_options.only_c) unreachable;
         switch (base.tag) {

src/link/Coff.zig

@@ -1727,13 +1727,8 @@ pub fn getDeclVAddr(self: *Coff, decl_index: Module.Decl.Index, reloc_info: link
     return 0;
 }
 
-pub fn getAnonDeclVAddr(
-    self: *Coff,
-    decl_val: InternPool.Index,
-    reloc_info: link.File.RelocInfo,
-) !u64 {
-    // This is basically the same as lowerUnnamedConst except it needs
-    // to return the same thing as `getDeclVAddr`
+pub fn lowerAnonDecl(self: *Coff, decl_val: InternPool.Index, src_loc: Module.SrcLoc) !codegen.Result {
+    // This is basically the same as lowerUnnamedConst.
     // example:
     // const ty = mod.intern_pool.typeOf(decl_val).toType();
     // const val = decl_val.toValue();
@@ -1742,6 +1737,13 @@ pub fn getAnonDeclVAddr(
     // be used by more than one function, however, its address is being used so we need
     // to put it in some location.
     // ...
+    _ = self;
+    _ = decl_val;
+    _ = src_loc;
+    _ = @panic("TODO: link/Coff lowerAnonDecl");
+}
+
+pub fn getAnonDeclVAddr(self: *Coff, decl_val: InternPool.Index, reloc_info: link.File.RelocInfo) !u64 {
     _ = self;
     _ = decl_val;
     _ = reloc_info;

src/link/Elf.zig

@@ -155,12 +155,14 @@ last_atom_and_free_list_table: std.AutoArrayHashMapUnmanaged(u16, LastAtomAndFre
 /// value assigned to label `foo` is an unnamed constant belonging/associated
 /// with `Decl` `main`, and lives as long as that `Decl`.
 unnamed_consts: UnnamedConstTable = .{},
+anon_decls: AnonDeclTable = .{},
 
 comdat_groups: std.ArrayListUnmanaged(ComdatGroup) = .{},
 comdat_groups_owners: std.ArrayListUnmanaged(ComdatGroupOwner) = .{},
 comdat_groups_table: std.AutoHashMapUnmanaged(u32, ComdatGroupOwner.Index) = .{},
 
 const UnnamedConstTable = std.AutoHashMapUnmanaged(Module.Decl.Index, std.ArrayListUnmanaged(Symbol.Index));
+const AnonDeclTable = std.AutoHashMapUnmanaged(InternPool.Index, Symbol.Index);
 const LazySymbolTable = std.AutoArrayHashMapUnmanaged(Module.Decl.OptionalIndex, LazySymbolMetadata);
 
 /// When allocating, the ideal_capacity is calculated by
@@ -321,6 +323,7 @@ pub fn deinit(self: *Elf) void {
         }
         self.unnamed_consts.deinit(gpa);
     }
+    self.anon_decls.deinit(gpa);
 
     if (self.dwarf) |*dw| {
         dw.deinit();
@@ -348,13 +351,8 @@ pub fn getDeclVAddr(self: *Elf, decl_index: Module.Decl.Index, reloc_info: link.
     return vaddr;
 }
 
-pub fn getAnonDeclVAddr(
-    self: *Elf,
-    decl_val: InternPool.Index,
-    reloc_info: link.File.RelocInfo,
-) !u64 {
-    // This is basically the same as lowerUnnamedConst except it needs
-    // to return the same thing as `getDeclVAddr`
+pub fn lowerAnonDecl(self: *Elf, decl_val: InternPool.Index, src_loc: Module.SrcLoc) !codegen.Result {
+    // This is basically the same as lowerUnnamedConst.
     // example:
     // const ty = mod.intern_pool.typeOf(decl_val).toType();
     // const val = decl_val.toValue();
@@ -363,10 +361,44 @@ pub fn getAnonDeclVAddr(
     // be used by more than one function, however, its address is being used so we need
     // to put it in some location.
     // ...
-    _ = self;
-    _ = decl_val;
-    _ = reloc_info;
-    _ = @panic("TODO: link/Elf getAnonDeclVAddr");
+    const gpa = self.base.allocator;
+    const gop = try self.anon_decls.getOrPut(gpa, decl_val);
+    if (!gop.found_existing) {
+        const mod = self.base.options.module.?;
+        const ty = mod.intern_pool.typeOf(decl_val).toType();
+        const val = decl_val.toValue();
+        const tv = TypedValue{ .ty = ty, .val = val };
+        const name = try std.fmt.allocPrint(gpa, "__anon_{d}", .{@intFromEnum(decl_val)});
+        defer gpa.free(name);
+        const res = self.lowerConst(name, tv, self.rodata_section_index.?, src_loc) catch |err| switch (err) {
+            else => {
+                // TODO improve error message
+                const em = try Module.ErrorMsg.create(gpa, src_loc, "lowerAnonDecl failed with error: {s}", .{
+                    @errorName(err),
+                });
+                return .{ .fail = em };
+            },
+        };
+        const sym_index = switch (res) {
+            .ok => |sym_index| sym_index,
+            .fail => |em| return .{ .fail = em },
+        };
+        gop.value_ptr.* = sym_index;
+    }
+    return .ok;
+}
+
+pub fn getAnonDeclVAddr(self: *Elf, decl_val: InternPool.Index, reloc_info: link.File.RelocInfo) !u64 {
+    const sym_index = self.anon_decls.get(decl_val).?;
+    const sym = self.symbol(sym_index);
+    const vaddr = sym.value;
+    const parent_atom = self.symbol(reloc_info.parent_atom_index).atom(self).?;
+    try parent_atom.addReloc(self, .{
+        .r_offset = reloc_info.offset,
+        .r_info = (@as(u64, @intCast(sym.esym_index)) << 32) | elf.R_X86_64_64,
+        .r_addend = reloc_info.addend,
+    });
+    return vaddr;
 }
 
 /// Returns end pos of collision, if any.
@@ -3126,36 +3158,19 @@ fn updateLazySymbol(self: *Elf, sym: link.File.LazySymbol, symbol_index: Symbol.
 
 pub fn lowerUnnamedConst(self: *Elf, typed_value: TypedValue, decl_index: Module.Decl.Index) !u32 {
     const gpa = self.base.allocator;
-
-    var code_buffer = std.ArrayList(u8).init(gpa);
-    defer code_buffer.deinit();
-
     const mod = self.base.options.module.?;
     const gop = try self.unnamed_consts.getOrPut(gpa, decl_index);
     if (!gop.found_existing) {
         gop.value_ptr.* = .{};
     }
     const unnamed_consts = gop.value_ptr;
-
     const decl = mod.declPtr(decl_index);
-    const name_str_index = blk: {
-        const decl_name = mod.intern_pool.stringToSlice(try decl.getFullyQualifiedName(mod));
-        const index = unnamed_consts.items.len;
-        const name = try std.fmt.allocPrint(gpa, "__unnamed_{s}_{d}", .{ decl_name, index });
-        defer gpa.free(name);
-        break :blk try self.strtab.insert(gpa, name);
-    };
-
-    const zig_module = self.file(self.zig_module_index.?).?.zig_module;
-    const sym_index = try zig_module.addAtom(self);
-
-    const res = try codegen.generateSymbol(&self.base, decl.srcLoc(mod), typed_value, &code_buffer, .{
-        .none = {},
-    }, .{
-        .parent_atom_index = sym_index,
-    });
-    const code = switch (res) {
-        .ok => code_buffer.items,
+    const decl_name = mod.intern_pool.stringToSlice(try decl.getFullyQualifiedName(mod));
+    const index = unnamed_consts.items.len;
+    const name = try std.fmt.allocPrint(gpa, "__unnamed_{s}_{d}", .{ decl_name, index });
+    defer gpa.free(name);
+    const sym_index = switch (try self.lowerConst(name, typed_value, self.rodata_section_index.?, decl.srcLoc(mod))) {
+        .ok => |sym_index| sym_index,
         .fail => |em| {
             decl.analysis = .codegen_failure;
             try mod.failed_decls.put(mod.gpa, decl_index, em);
@@ -3163,13 +3178,48 @@ pub fn lowerUnnamedConst(self: *Elf, typed_value: TypedValue, decl_index: Module
             return error.CodegenFail;
         },
     };
+    const sym = self.symbol(sym_index);
+    try unnamed_consts.append(gpa, sym.atom_index);
+    return sym_index;
+}
 
-    const required_alignment = typed_value.ty.abiAlignment(mod);
-    const shdr_index = self.rodata_section_index.?;
-    const phdr_index = self.phdr_to_shdr_table.get(shdr_index).?;
+const LowerConstResult = union(enum) {
+    ok: Symbol.Index,
+    fail: *Module.ErrorMsg,
+};
+
+fn lowerConst(
+    self: *Elf,
+    name: []const u8,
+    tv: TypedValue,
+    output_section_index: u16,
+    src_loc: Module.SrcLoc,
+) !LowerConstResult {
+    const gpa = self.base.allocator;
+
+    var code_buffer = std.ArrayList(u8).init(gpa);
+    defer code_buffer.deinit();
+
+    const mod = self.base.options.module.?;
+    const zig_module = self.file(self.zig_module_index.?).?.zig_module;
+    const sym_index = try zig_module.addAtom(self);
+
+    const res = try codegen.generateSymbol(&self.base, src_loc, tv, &code_buffer, .{
+        .none = {},
+    }, .{
+        .parent_atom_index = sym_index,
+    });
+    const code = switch (res) {
+        .ok => code_buffer.items,
+        .fail => |em| return .{ .fail = em },
+    };
+
+    const required_alignment = tv.ty.abiAlignment(mod);
+    const phdr_index = self.phdr_to_shdr_table.get(output_section_index).?;
     const local_sym = self.symbol(sym_index);
+    const name_str_index = try self.strtab.insert(gpa, name);
     local_sym.name_offset = name_str_index;
-    local_sym.output_section_index = self.rodata_section_index.?;
+    local_sym.output_section_index = output_section_index;
     const local_esym = &zig_module.local_esyms.items[local_sym.esym_index];
     local_esym.st_name = name_str_index;
     local_esym.st_info |= elf.STT_OBJECT;
@@ -3179,21 +3229,20 @@ pub fn lowerUnnamedConst(self: *Elf, typed_value: TypedValue, decl_index: Module
     atom_ptr.name_offset = name_str_index;
     atom_ptr.alignment = required_alignment;
     atom_ptr.size = code.len;
-    atom_ptr.output_section_index = self.rodata_section_index.?;
+    atom_ptr.output_section_index = output_section_index;
 
     try atom_ptr.allocate(self);
+    // TODO rename and re-audit this method
     errdefer self.freeDeclMetadata(sym_index);
 
     local_sym.value = atom_ptr.value;
     local_esym.st_value = atom_ptr.value;
 
-    try unnamed_consts.append(gpa, atom_ptr.atom_index);
-
     const section_offset = atom_ptr.value - self.phdrs.items[phdr_index].p_vaddr;
-    const file_offset = self.shdrs.items[shdr_index].sh_offset + section_offset;
+    const file_offset = self.shdrs.items[output_section_index].sh_offset + section_offset;
     try self.base.file.?.pwriteAll(code, file_offset);
 
-    return sym_index;
+    return .{ .ok = sym_index };
 }
 
 pub fn updateDeclExports(

src/link/MachO.zig

@@ -2840,13 +2840,8 @@ pub fn getDeclVAddr(self: *MachO, decl_index: Module.Decl.Index, reloc_info: Fil
     return 0;
 }
 
-pub fn getAnonDeclVAddr(
-    self: *MachO,
-    decl_val: InternPool.Index,
-    reloc_info: link.File.RelocInfo,
-) !u64 {
-    // This is basically the same as lowerUnnamedConst except it needs
-    // to return the same thing as `getDeclVAddr`
+pub fn lowerAnonDecl(self: *MachO, decl_val: InternPool.Index, src_loc: Module.SrcLoc) !codegen.Result {
+    // This is basically the same as lowerUnnamedConst.
     // example:
     // const ty = mod.intern_pool.typeOf(decl_val).toType();
     // const val = decl_val.toValue();
@@ -2855,6 +2850,13 @@ pub fn getAnonDeclVAddr(
     // be used by more than one function, however, its address is being used so we need
     // to put it in some location.
     // ...
+    _ = self;
+    _ = decl_val;
+    _ = src_loc;
+    _ = @panic("TODO: link/MachO lowerAnonDecl");
+}
+
+pub fn getAnonDeclVAddr(self: *MachO, decl_val: InternPool.Index, reloc_info: link.File.RelocInfo) !u64 {
     _ = self;
     _ = decl_val;
     _ = reloc_info;

src/link/Plan9.zig

@@ -1418,13 +1418,8 @@ pub fn getDeclVAddr(
     return undefined;
 }
 
-pub fn getAnonDeclVAddr(
-    self: *Plan9,
-    decl_val: InternPool.Index,
-    reloc_info: link.File.RelocInfo,
-) !u64 {
-    // This is basically the same as lowerUnnamedConst except it needs
-    // to return the same thing as `getDeclVAddr`
+pub fn lowerAnonDecl(self: *Plan9, decl_val: InternPool.Index, src_loc: Module.SrcLoc) !codegen.Result {
+    // This is basically the same as lowerUnnamedConst.
     // example:
     // const ty = mod.intern_pool.typeOf(decl_val).toType();
     // const val = decl_val.toValue();
@@ -1433,6 +1428,13 @@ pub fn getAnonDeclVAddr(
     // be used by more than one function, however, its address is being used so we need
     // to put it in some location.
     // ...
+    _ = self;
+    _ = decl_val;
+    _ = src_loc;
+    _ = @panic("TODO: link/Plan9 lowerAnonDecl");
+}
+
+pub fn getAnonDeclVAddr(self: *Plan9, decl_val: InternPool.Index, reloc_info: link.File.RelocInfo) !u64 {
     _ = self;
     _ = decl_val;
     _ = reloc_info;

src/link/Wasm.zig

@@ -1679,13 +1679,8 @@ pub fn getDeclVAddr(
     return target_symbol_index;
 }
 
-pub fn getAnonDeclVAddr(
-    wasm: *Wasm,
-    decl_val: InternPool.Index,
-    reloc_info: link.File.RelocInfo,
-) !u64 {
-    // This is basically the same as lowerUnnamedConst except it needs
-    // to return the same thing as `getDeclVAddr`
+pub fn lowerAnonDecl(self: *Wasm, decl_val: InternPool.Index, src_loc: Module.SrcLoc) !codegen.Result {
+    // This is basically the same as lowerUnnamedConst.
     // example:
     // const ty = mod.intern_pool.typeOf(decl_val).toType();
     // const val = decl_val.toValue();
@@ -1694,6 +1689,13 @@ pub fn getAnonDeclVAddr(
     // be used by more than one function, however, its address is being used so we need
     // to put it in some location.
     // ...
+    _ = self;
+    _ = decl_val;
+    _ = src_loc;
+    _ = @panic("TODO: link/Wasm lowerAnonDecl");
+}
+
+pub fn getAnonDeclVAddr(wasm: *Wasm, decl_val: InternPool.Index, reloc_info: link.File.RelocInfo) !u64 {
     _ = wasm;
     _ = decl_val;
     _ = reloc_info;