x86_64: cleanup lazy symbols

In theory fixes updating lazy symbols during incremental compilation.

3 files changed, 131 insertions, 99 deletions

diff --git a/src/link/Coff.zig b/src/link/Coff.zig
index 41d4617e53..81e8c57bdd 100644
--- a/src/link/Coff.zig
+++ b/src/link/Coff.zig
@@ -143,8 +143,11 @@ const Section = struct {
 const LazySymbolTable = std.AutoArrayHashMapUnmanaged(Module.Decl.OptionalIndex, LazySymbolMetadata);
 
 const LazySymbolMetadata = struct {
-    text_atom: ?Atom.Index = null,
-    rdata_atom: ?Atom.Index = null,
+    const State = enum { unused, pending_flush, flushed };
+    text_atom: Atom.Index = undefined,
+    rdata_atom: Atom.Index = undefined,
+    text_state: State = .unused,
+    rdata_state: State = .unused,
 };
 
 const DeclMetadata = struct {
@@ -1150,8 +1153,6 @@ pub fn updateDecl(
     const tracy = trace(@src());
     defer tracy.end();
 
-    try self.updateLazySymbol(decl_index);
-
     const decl = module.declPtr(decl_index);
 
     if (decl.val.tag() == .extern_fn) {
@@ -1194,21 +1195,6 @@ pub fn updateDecl(
     return self.updateDeclExports(module, decl_index, module.getDeclExports(decl_index));
 }
 
-fn updateLazySymbol(self: *Coff, decl: ?Module.Decl.Index) !void {
-    const metadata = self.lazy_syms.get(Module.Decl.OptionalIndex.init(decl)) orelse return;
-    const mod = self.base.options.module.?;
-    if (metadata.text_atom) |atom| try self.updateLazySymbolAtom(
-        link.File.LazySymbol.initDecl(.code, decl, mod),
-        atom,
-        self.text_section_index.?,
-    );
-    if (metadata.rdata_atom) |atom| try self.updateLazySymbolAtom(
-        link.File.LazySymbol.initDecl(.const_data, decl, mod),
-        atom,
-        self.rdata_section_index.?,
-    );
-}
-
 fn updateLazySymbolAtom(
     self: *Coff,
     sym: link.File.LazySymbol,
@@ -1279,14 +1265,19 @@ pub fn getOrCreateAtomForLazySymbol(self: *Coff, sym: link.File.LazySymbol) !Ato
     const gop = try self.lazy_syms.getOrPut(self.base.allocator, sym.getDecl());
     errdefer _ = if (!gop.found_existing) self.lazy_syms.pop();
     if (!gop.found_existing) gop.value_ptr.* = .{};
-    const atom_ptr = switch (sym.kind) {
-        .code => &gop.value_ptr.text_atom,
-        .const_data => &gop.value_ptr.rdata_atom,
+    const metadata: struct { atom: *Atom.Index, state: *LazySymbolMetadata.State } = switch (sym.kind) {
+        .code => .{ .atom = &gop.value_ptr.text_atom, .state = &gop.value_ptr.text_state },
+        .const_data => .{ .atom = &gop.value_ptr.rdata_atom, .state = &gop.value_ptr.rdata_state },
     };
-    if (atom_ptr.*) |atom| return atom;
-    const atom = try self.createAtom();
-    atom_ptr.* = atom;
-    try self.updateLazySymbolAtom(sym, atom, switch (sym.kind) {
+    switch (metadata.state.*) {
+        .unused => metadata.atom.* = try self.createAtom(),
+        .pending_flush => return metadata.atom.*,
+        .flushed => {},
+    }
+    metadata.state.* = .pending_flush;
+    const atom = metadata.atom.*;
+    // anyerror needs to be deferred until flushModule
+    if (sym.getDecl() != .none) try self.updateLazySymbolAtom(sym, atom, switch (sym.kind) {
         .code => self.text_section_index.?,
         .const_data => self.rdata_section_index.?,
     });
@@ -1617,15 +1608,35 @@ pub fn flushModule(self: *Coff, comp: *Compilation, prog_node: *std.Progress.Nod
     sub_prog_node.activate();
     defer sub_prog_node.end();
 
-    // Most lazy symbols can be updated when the corresponding decl is,
-    // so we only have to worry about the one without an associated decl.
-    self.updateLazySymbol(null) catch |err| switch (err) {
-        error.CodegenFail => return error.FlushFailure,
-        else => |e| return e,
-    };
-
     const gpa = self.base.allocator;
 
+    const module = self.base.options.module orelse return error.LinkingWithoutZigSourceUnimplemented;
+
+    if (self.lazy_syms.getPtr(.none)) |metadata| {
+        // Most lazy symbols can be updated on first use, but
+        // anyerror needs to wait for everything to be flushed.
+        if (metadata.text_state != .unused) self.updateLazySymbolAtom(
+            link.File.LazySymbol.initDecl(.code, null, module),
+            metadata.text_atom,
+            self.text_section_index.?,
+        ) catch |err| return switch (err) {
+            error.CodegenFail => error.FlushFailure,
+            else => |e| e,
+        };
+        if (metadata.rdata_state != .unused) self.updateLazySymbolAtom(
+            link.File.LazySymbol.initDecl(.const_data, null, module),
+            metadata.rdata_atom,
+            self.rdata_section_index.?,
+        ) catch |err| return switch (err) {
+            error.CodegenFail => error.FlushFailure,
+            else => |e| e,
+        };
+    }
+    for (self.lazy_syms.values()) |*metadata| {
+        if (metadata.text_state != .unused) metadata.text_state = .flushed;
+        if (metadata.rdata_state != .unused) metadata.rdata_state = .flushed;
+    }
+
     while (self.unresolved.popOrNull()) |entry| {
         assert(entry.value); // We only expect imports generated by the incremental linker for now.
         const global = self.globals.items[entry.key];
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index ec113e5c8a..724ec76500 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -65,8 +65,11 @@ const Section = struct {
 };
 
 const LazySymbolMetadata = struct {
-    text_atom: ?Atom.Index = null,
-    rodata_atom: ?Atom.Index = null,
+    const State = enum { unused, pending_flush, flushed };
+    text_atom: Atom.Index = undefined,
+    rodata_atom: Atom.Index = undefined,
+    text_state: State = .unused,
+    rodata_state: State = .unused,
 };
 
 const DeclMetadata = struct {
@@ -1032,17 +1035,35 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
     sub_prog_node.activate();
     defer sub_prog_node.end();
 
-    // Most lazy symbols can be updated when the corresponding decl is,
-    // so we only have to worry about the one without an associated decl.
-    self.updateLazySymbol(null) catch |err| switch (err) {
-        error.CodegenFail => return error.FlushFailure,
-        else => |e| return e,
-    };
-
     // TODO This linker code currently assumes there is only 1 compilation unit and it
     // corresponds to the Zig source code.
     const module = self.base.options.module orelse return error.LinkingWithoutZigSourceUnimplemented;
 
+    if (self.lazy_syms.getPtr(.none)) |metadata| {
+        // Most lazy symbols can be updated on first use, but
+        // anyerror needs to wait for everything to be flushed.
+        if (metadata.text_state != .unused) self.updateLazySymbolAtom(
+            File.LazySymbol.initDecl(.code, null, module),
+            metadata.text_atom,
+            self.text_section_index.?,
+        ) catch |err| return switch (err) {
+            error.CodegenFail => error.FlushFailure,
+            else => |e| e,
+        };
+        if (metadata.rodata_state != .unused) self.updateLazySymbolAtom(
+            File.LazySymbol.initDecl(.const_data, null, module),
+            metadata.rodata_atom,
+            self.rodata_section_index.?,
+        ) catch |err| return switch (err) {
+            error.CodegenFail => error.FlushFailure,
+            else => |e| e,
+        };
+    }
+    for (self.lazy_syms.values()) |*metadata| {
+        if (metadata.text_state != .unused) metadata.text_state = .flushed;
+        if (metadata.rodata_state != .unused) metadata.rodata_state = .flushed;
+    }
+
     const target_endian = self.base.options.target.cpu.arch.endian();
     const foreign_endian = target_endian != builtin.cpu.arch.endian();
 
@@ -2378,14 +2399,19 @@ pub fn getOrCreateAtomForLazySymbol(self: *Elf, sym: File.LazySymbol) !Atom.Inde
     const gop = try self.lazy_syms.getOrPut(self.base.allocator, sym.getDecl());
     errdefer _ = if (!gop.found_existing) self.lazy_syms.pop();
     if (!gop.found_existing) gop.value_ptr.* = .{};
-    const atom_ptr = switch (sym.kind) {
-        .code => &gop.value_ptr.text_atom,
-        .const_data => &gop.value_ptr.rodata_atom,
+    const metadata: struct { atom: *Atom.Index, state: *LazySymbolMetadata.State } = switch (sym.kind) {
+        .code => .{ .atom = &gop.value_ptr.text_atom, .state = &gop.value_ptr.text_state },
+        .const_data => .{ .atom = &gop.value_ptr.rodata_atom, .state = &gop.value_ptr.rodata_state },
     };
-    if (atom_ptr.*) |atom| return atom;
-    const atom = try self.createAtom();
-    atom_ptr.* = atom;
-    try self.updateLazySymbolAtom(sym, atom, switch (sym.kind) {
+    switch (metadata.state.*) {
+        .unused => metadata.atom.* = try self.createAtom(),
+        .pending_flush => return metadata.atom.*,
+        .flushed => {},
+    }
+    metadata.state.* = .pending_flush;
+    const atom = metadata.atom.*;
+    // anyerror needs to be deferred until flushModule
+    if (sym.getDecl() != .none) try self.updateLazySymbolAtom(sym, atom, switch (sym.kind) {
         .code => self.text_section_index.?,
         .const_data => self.rodata_section_index.?,
     });
@@ -2598,8 +2624,6 @@ pub fn updateDecl(
     const tracy = trace(@src());
     defer tracy.end();
 
-    try self.updateLazySymbol(decl_index);
-
     const decl = module.declPtr(decl_index);
 
     if (decl.val.tag() == .extern_fn) {
@@ -2666,21 +2690,6 @@ pub fn updateDecl(
     return self.updateDeclExports(module, decl_index, module.getDeclExports(decl_index));
 }
 
-fn updateLazySymbol(self: *Elf, decl: ?Module.Decl.Index) !void {
-    const metadata = self.lazy_syms.get(Module.Decl.OptionalIndex.init(decl)) orelse return;
-    const mod = self.base.options.module.?;
-    if (metadata.text_atom) |atom| try self.updateLazySymbolAtom(
-        File.LazySymbol.initDecl(.code, decl, mod),
-        atom,
-        self.text_section_index.?,
-    );
-    if (metadata.rodata_atom) |atom| try self.updateLazySymbolAtom(
-        File.LazySymbol.initDecl(.const_data, decl, mod),
-        atom,
-        self.rodata_section_index.?,
-    );
-}
-
 fn updateLazySymbolAtom(
     self: *Elf,
     sym: File.LazySymbol,
diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 458b283d4f..a346ec756f 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -236,8 +236,11 @@ const is_hot_update_compatible = switch (builtin.target.os.tag) {
 const LazySymbolTable = std.AutoArrayHashMapUnmanaged(Module.Decl.OptionalIndex, LazySymbolMetadata);
 
 const LazySymbolMetadata = struct {
-    text_atom: ?Atom.Index = null,
-    data_const_atom: ?Atom.Index = null,
+    const State = enum { unused, pending_flush, flushed };
+    text_atom: Atom.Index = undefined,
+    data_const_atom: Atom.Index = undefined,
+    text_state: State = .unused,
+    data_const_state: State = .unused,
 };
 
 const TlvSymbolTable = std.AutoArrayHashMapUnmanaged(SymbolWithLoc, Atom.Index);
@@ -493,15 +496,33 @@ pub fn flushModule(self: *MachO, comp: *Compilation, prog_node: *std.Progress.No
     sub_prog_node.activate();
     defer sub_prog_node.end();
 
-    // Most lazy symbols can be updated when the corresponding decl is,
-    // so we only have to worry about the one without an associated decl.
-    self.updateLazySymbol(null) catch |err| switch (err) {
-        error.CodegenFail => return error.FlushFailure,
-        else => |e| return e,
-    };
-
     const module = self.base.options.module orelse return error.LinkingWithoutZigSourceUnimplemented;
 
+    if (self.lazy_syms.getPtr(.none)) |metadata| {
+        // Most lazy symbols can be updated on first use, but
+        // anyerror needs to wait for everything to be flushed.
+        if (metadata.text_state != .unused) self.updateLazySymbolAtom(
+            File.LazySymbol.initDecl(.code, null, module),
+            metadata.text_atom,
+            self.text_section_index.?,
+        ) catch |err| return switch (err) {
+            error.CodegenFail => error.FlushFailure,
+            else => |e| e,
+        };
+        if (metadata.data_const_state != .unused) self.updateLazySymbolAtom(
+            File.LazySymbol.initDecl(.const_data, null, module),
+            metadata.data_const_atom,
+            self.data_const_section_index.?,
+        ) catch |err| return switch (err) {
+            error.CodegenFail => error.FlushFailure,
+            else => |e| e,
+        };
+    }
+    for (self.lazy_syms.values()) |*metadata| {
+        if (metadata.text_state != .unused) metadata.text_state = .flushed;
+        if (metadata.data_const_state != .unused) metadata.data_const_state = .flushed;
+    }
+
     if (self.d_sym) |*d_sym| {
         try d_sym.dwarf.flushModule(module);
     }
@@ -1960,8 +1981,6 @@ pub fn updateDecl(self: *MachO, module: *Module, decl_index: Module.Decl.Index)
     const tracy = trace(@src());
     defer tracy.end();
 
-    try self.updateLazySymbol(decl_index);
-
     const decl = module.declPtr(decl_index);
 
     if (decl.val.tag() == .extern_fn) {
@@ -2036,21 +2055,6 @@ pub fn updateDecl(self: *MachO, module: *Module, decl_index: Module.Decl.Index)
     try self.updateDeclExports(module, decl_index, module.getDeclExports(decl_index));
 }
 
-fn updateLazySymbol(self: *MachO, decl: ?Module.Decl.Index) !void {
-    const metadata = self.lazy_syms.get(Module.Decl.OptionalIndex.init(decl)) orelse return;
-    const mod = self.base.options.module.?;
-    if (metadata.text_atom) |atom| try self.updateLazySymbolAtom(
-        File.LazySymbol.initDecl(.code, decl, mod),
-        atom,
-        self.text_section_index.?,
-    );
-    if (metadata.data_const_atom) |atom| try self.updateLazySymbolAtom(
-        File.LazySymbol.initDecl(.const_data, decl, mod),
-        atom,
-        self.data_const_section_index.?,
-    );
-}
-
 fn updateLazySymbolAtom(
     self: *MachO,
     sym: File.LazySymbol,
@@ -2125,14 +2129,22 @@ pub fn getOrCreateAtomForLazySymbol(self: *MachO, sym: File.LazySymbol) !Atom.In
     const gop = try self.lazy_syms.getOrPut(self.base.allocator, sym.getDecl());
     errdefer _ = if (!gop.found_existing) self.lazy_syms.pop();
     if (!gop.found_existing) gop.value_ptr.* = .{};
-    const atom_ptr = switch (sym.kind) {
-        .code => &gop.value_ptr.text_atom,
-        .const_data => &gop.value_ptr.data_const_atom,
+    const metadata: struct { atom: *Atom.Index, state: *LazySymbolMetadata.State } = switch (sym.kind) {
+        .code => .{ .atom = &gop.value_ptr.text_atom, .state = &gop.value_ptr.text_state },
+        .const_data => .{
+            .atom = &gop.value_ptr.data_const_atom,
+            .state = &gop.value_ptr.data_const_state,
+        },
     };
-    if (atom_ptr.*) |atom| return atom;
-    const atom = try self.createAtom();
-    atom_ptr.* = atom;
-    try self.updateLazySymbolAtom(sym, atom, switch (sym.kind) {
+    switch (metadata.state.*) {
+        .unused => metadata.atom.* = try self.createAtom(),
+        .pending_flush => return metadata.atom.*,
+        .flushed => {},
+    }
+    metadata.state.* = .pending_flush;
+    const atom = metadata.atom.*;
+    // anyerror needs to be deferred until flushModule
+    if (sym.getDecl() != .none) try self.updateLazySymbolAtom(sym, atom, switch (sym.kind) {
         .code => self.text_section_index.?,
         .const_data => self.data_const_section_index.?,
     });