x86_64: add support for pie executables

2 files changed, 95 insertions, 62 deletions

diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index c68abc06ce..3b8ab52982 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -2255,19 +2255,30 @@ pub const DeclGen = struct {
     fn renderFwdDecl(
         dg: *DeclGen,
         nav_index: InternPool.Nav.Index,
-        flags: struct {
-            is_extern: bool,
+        flags: packed struct {
             is_const: bool,
             is_threadlocal: bool,
-            is_weak_linkage: bool,
+            linkage: std.builtin.GlobalLinkage,
+            visibility: std.builtin.SymbolVisibility,
         },
     ) !void {
         const zcu = dg.pt.zcu;
         const ip = &zcu.intern_pool;
         const nav = ip.getNav(nav_index);
         const fwd = dg.fwdDeclWriter();
-        try fwd.writeAll(if (flags.is_extern) "zig_extern " else "static ");
-        if (flags.is_weak_linkage) try fwd.writeAll("zig_weak_linkage ");
+        try fwd.writeAll(switch (flags.linkage) {
+            .internal => "static ",
+            .strong, .weak, .link_once => "zig_extern ",
+        });
+        switch (flags.linkage) {
+            .internal, .strong => {},
+            .weak => try fwd.writeAll("zig_weak_linkage "),
+            .link_once => return dg.fail("TODO: CBE: implement linkonce linkage?", .{}),
+        }
+        switch (flags.linkage) {
+            .internal => {},
+            .strong, .weak, .link_once => try fwd.print("zig_visibility({s}) ", .{@tagName(flags.visibility)}),
+        }
         if (flags.is_threadlocal and !dg.mod.single_threaded) try fwd.writeAll("zig_threadlocal ");
         try dg.renderTypeAndName(
             fwd,
@@ -2994,10 +3005,10 @@ pub fn genDecl(o: *Object) !void {
     switch (ip.indexToKey(nav.status.fully_resolved.val)) {
         .@"extern" => |@"extern"| {
             if (!ip.isFunctionType(nav_ty.toIntern())) return o.dg.renderFwdDecl(o.dg.pass.nav, .{
-                .is_extern = true,
                 .is_const = @"extern".is_const,
                 .is_threadlocal = @"extern".is_threadlocal,
-                .is_weak_linkage = @"extern".is_weak_linkage,
+                .linkage = @"extern".linkage,
+                .visibility = @"extern".visibility,
             });
 
             const fwd = o.dg.fwdDeclWriter();
@@ -3016,13 +3027,12 @@ pub fn genDecl(o: *Object) !void {
         },
         .variable => |variable| {
             try o.dg.renderFwdDecl(o.dg.pass.nav, .{
-                .is_extern = false,
                 .is_const = false,
                 .is_threadlocal = variable.is_threadlocal,
-                .is_weak_linkage = variable.is_weak_linkage,
+                .linkage = .internal,
+                .visibility = .default,
             });
             const w = o.writer();
-            if (variable.is_weak_linkage) try w.writeAll("zig_weak_linkage ");
             if (variable.is_threadlocal and !o.dg.mod.single_threaded) try w.writeAll("zig_threadlocal ");
             if (nav.status.fully_resolved.@"linksection".toSlice(&zcu.intern_pool)) |s|
                 try w.print("zig_linksection({s}) ", .{fmtStringLiteral(s, null)});
@@ -3467,7 +3477,7 @@ fn genBodyInner(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail,
             .error_set_has_value => return f.fail("TODO: C backend: implement error_set_has_value", .{}),
             .vector_store_elem => return f.fail("TODO: C backend: implement vector_store_elem", .{}),
 
-            .tlv_dllimport_ptr => try airTlvDllimportPtr(f, inst),
+            .runtime_nav_ptr => try airRuntimeNavPtr(f, inst),
 
             .c_va_start => try airCVaStart(f, inst),
             .c_va_arg => try airCVaArg(f, inst),
@@ -7672,7 +7682,7 @@ fn airMulAdd(f: *Function, inst: Air.Inst.Index) !CValue {
     return local;
 }
 
-fn airTlvDllimportPtr(f: *Function, inst: Air.Inst.Index) !CValue {
+fn airRuntimeNavPtr(f: *Function, inst: Air.Inst.Index) !CValue {
     const ty_nav = f.air.instructions.items(.data)[@intFromEnum(inst)].ty_nav;
     const writer = f.object.writer();
     const local = try f.allocLocal(inst, .fromInterned(ty_nav.ty));
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 7790840d20..3fc6250d3f 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -2979,36 +2979,49 @@ pub const Object = struct {
         const zcu = pt.zcu;
         const ip = &zcu.intern_pool;
         const nav = ip.getNav(nav_index);
-        const is_extern, const is_threadlocal, const is_weak_linkage, const is_dll_import = switch (nav.status) {
+        const linkage: std.builtin.GlobalLinkage, const visibility: Builder.Visibility, const is_threadlocal, const is_dll_import = switch (nav.status) {
             .unresolved => unreachable,
             .fully_resolved => |r| switch (ip.indexToKey(r.val)) {
-                .variable => |variable| .{ false, variable.is_threadlocal, variable.is_weak_linkage, false },
-                .@"extern" => |@"extern"| .{ true, @"extern".is_threadlocal, @"extern".is_weak_linkage, @"extern".is_dll_import },
-                else => .{ false, false, false, false },
+                .variable => |variable| .{ .internal, .default, variable.is_threadlocal, false },
+                .@"extern" => |@"extern"| .{ @"extern".linkage, .fromSymbolVisibility(@"extern".visibility), @"extern".is_threadlocal, @"extern".is_dll_import },
+                else => .{ .internal, .default, false, false },
             },
             // This means it's a source declaration which is not `extern`!
-            .type_resolved => |r| .{ false, r.is_threadlocal, false, false },
+            .type_resolved => |r| .{ .internal, .default, r.is_threadlocal, false },
         };
 
         const variable_index = try o.builder.addVariable(
-            try o.builder.strtabString((if (is_extern) nav.name else nav.fqn).toSlice(ip)),
+            try o.builder.strtabString(switch (linkage) {
+                .internal => nav.fqn,
+                .strong, .weak => nav.name,
+                .link_once => unreachable,
+            }.toSlice(ip)),
             try o.lowerType(Type.fromInterned(nav.typeOf(ip))),
             toLlvmGlobalAddressSpace(nav.getAddrspace(), zcu.getTarget()),
         );
         gop.value_ptr.* = variable_index.ptrConst(&o.builder).global;
 
         // This is needed for declarations created by `@extern`.
-        if (is_extern) {
-            variable_index.setLinkage(.external, &o.builder);
-            variable_index.setUnnamedAddr(.default, &o.builder);
-            if (is_threadlocal and !zcu.navFileScope(nav_index).mod.?.single_threaded)
-                variable_index.setThreadLocal(.generaldynamic, &o.builder);
-            if (is_weak_linkage) variable_index.setLinkage(.extern_weak, &o.builder);
-            if (is_dll_import) variable_index.setDllStorageClass(.dllimport, &o.builder);
-        } else {
-            variable_index.setLinkage(.internal, &o.builder);
-            variable_index.setUnnamedAddr(.unnamed_addr, &o.builder);
-        }
+        switch (linkage) {
+            .internal => {
+                variable_index.setLinkage(.internal, &o.builder);
+                variable_index.setUnnamedAddr(.unnamed_addr, &o.builder);
+            },
+            .strong, .weak => {
+                variable_index.setLinkage(switch (linkage) {
+                    .internal => unreachable,
+                    .strong => .external,
+                    .weak => .extern_weak,
+                    .link_once => unreachable,
+                }, &o.builder);
+                variable_index.setUnnamedAddr(.default, &o.builder);
+                if (is_threadlocal and !zcu.navFileScope(nav_index).mod.?.single_threaded)
+                    variable_index.setThreadLocal(.generaldynamic, &o.builder);
+                if (is_dll_import) variable_index.setDllStorageClass(.dllimport, &o.builder);
+            },
+            .link_once => unreachable,
+        }
+        variable_index.setVisibility(visibility, &o.builder);
         return variable_index;
     }
 
@@ -4530,14 +4543,14 @@ pub const NavGen = struct {
         const nav = ip.getNav(nav_index);
         const resolved = nav.status.fully_resolved;
 
-        const is_extern, const lib_name, const is_threadlocal, const is_weak_linkage, const is_dll_import, const is_const, const init_val, const owner_nav = switch (ip.indexToKey(resolved.val)) {
-            .variable => |variable| .{ false, .none, variable.is_threadlocal, variable.is_weak_linkage, false, false, variable.init, variable.owner_nav },
-            .@"extern" => |@"extern"| .{ true, @"extern".lib_name, @"extern".is_threadlocal, @"extern".is_weak_linkage, @"extern".is_dll_import, @"extern".is_const, .none, @"extern".owner_nav },
-            else => .{ false, .none, false, false, false, true, resolved.val, nav_index },
+        const lib_name, const linkage, const visibility: Builder.Visibility, const is_threadlocal, const is_dll_import, const is_const, const init_val, const owner_nav = switch (ip.indexToKey(resolved.val)) {
+            .variable => |variable| .{ .none, .internal, .default, variable.is_threadlocal, false, false, variable.init, variable.owner_nav },
+            .@"extern" => |@"extern"| .{ @"extern".lib_name, @"extern".linkage, .fromSymbolVisibility(@"extern".visibility), @"extern".is_threadlocal, @"extern".is_dll_import, @"extern".is_const, .none, @"extern".owner_nav },
+            else => .{ .none, .internal, .default, false, false, true, resolved.val, nav_index },
         };
         const ty = Type.fromInterned(nav.typeOf(ip));
 
-        if (is_extern and ip.isFunctionType(ty.toIntern())) {
+        if (linkage != .internal and ip.isFunctionType(ty.toIntern())) {
             _ = try o.resolveLlvmFunction(owner_nav);
         } else {
             const variable_index = try o.resolveGlobalNav(nav_index);
@@ -4549,6 +4562,7 @@ pub const NavGen = struct {
                 .none => .no_init,
                 else => try o.lowerValue(init_val),
             }, &o.builder);
+            variable_index.setVisibility(visibility, &o.builder);
 
             const file_scope = zcu.navFileScopeIndex(nav_index);
             const mod = zcu.fileByIndex(file_scope).mod.?;
@@ -4568,7 +4582,7 @@ pub const NavGen = struct {
                     line_number,
                     try o.lowerDebugType(ty),
                     variable_index,
-                    .{ .local = !is_extern },
+                    .{ .local = linkage == .internal },
                 );
 
                 const debug_expression = try o.builder.debugExpression(&.{});
@@ -4583,38 +4597,47 @@ pub const NavGen = struct {
             }
         }
 
-        if (is_extern) {
-            const global_index = o.nav_map.get(nav_index).?;
+        switch (linkage) {
+            .internal => {},
+            .strong, .weak => {
+                const global_index = o.nav_map.get(nav_index).?;
 
-            const decl_name = decl_name: {
-                if (zcu.getTarget().cpu.arch.isWasm() and ty.zigTypeTag(zcu) == .@"fn") {
-                    if (lib_name.toSlice(ip)) |lib_name_slice| {
-                        if (!std.mem.eql(u8, lib_name_slice, "c")) {
-                            break :decl_name try o.builder.strtabStringFmt("{}|{s}", .{ nav.name.fmt(ip), lib_name_slice });
+                const decl_name = decl_name: {
+                    if (zcu.getTarget().cpu.arch.isWasm() and ty.zigTypeTag(zcu) == .@"fn") {
+                        if (lib_name.toSlice(ip)) |lib_name_slice| {
+                            if (!std.mem.eql(u8, lib_name_slice, "c")) {
+                                break :decl_name try o.builder.strtabStringFmt("{}|{s}", .{ nav.name.fmt(ip), lib_name_slice });
+                            }
                         }
                     }
-                }
-                break :decl_name try o.builder.strtabString(nav.name.toSlice(ip));
-            };
+                    break :decl_name try o.builder.strtabString(nav.name.toSlice(ip));
+                };
 
-            if (o.builder.getGlobal(decl_name)) |other_global| {
-                if (other_global != global_index) {
-                    // Another global already has this name; just use it in place of this global.
-                    try global_index.replace(other_global, &o.builder);
-                    return;
+                if (o.builder.getGlobal(decl_name)) |other_global| {
+                    if (other_global != global_index) {
+                        // Another global already has this name; just use it in place of this global.
+                        try global_index.replace(other_global, &o.builder);
+                        return;
+                    }
                 }
-            }
 
-            try global_index.rename(decl_name, &o.builder);
-            global_index.setLinkage(.external, &o.builder);
-            global_index.setUnnamedAddr(.default, &o.builder);
-            if (is_dll_import) {
-                global_index.setDllStorageClass(.dllimport, &o.builder);
-            } else if (zcu.comp.config.dll_export_fns) {
-                global_index.setDllStorageClass(.default, &o.builder);
-            }
+                try global_index.rename(decl_name, &o.builder);
+                global_index.setUnnamedAddr(.default, &o.builder);
+                if (is_dll_import) {
+                    global_index.setDllStorageClass(.dllimport, &o.builder);
+                } else if (zcu.comp.config.dll_export_fns) {
+                    global_index.setDllStorageClass(.default, &o.builder);
+                }
 
-            if (is_weak_linkage) global_index.setLinkage(.extern_weak, &o.builder);
+                global_index.setLinkage(switch (linkage) {
+                    .internal => unreachable,
+                    .strong => .external,
+                    .weak => .extern_weak,
+                    .link_once => unreachable,
+                }, &o.builder);
+                global_index.setVisibility(visibility, &o.builder);
+            },
+            .link_once => unreachable,
         }
     }
 };
@@ -5023,7 +5046,7 @@ pub const FuncGen = struct {
 
                 .vector_store_elem => try self.airVectorStoreElem(inst),
 
-                .tlv_dllimport_ptr => try self.airTlvDllimportPtr(inst),
+                .runtime_nav_ptr => try self.airRuntimeNavPtr(inst),
 
                 .inferred_alloc, .inferred_alloc_comptime => unreachable,
 
@@ -8122,7 +8145,7 @@ pub const FuncGen = struct {
         return .none;
     }
 
-    fn airTlvDllimportPtr(fg: *FuncGen, inst: Air.Inst.Index) !Builder.Value {
+    fn airRuntimeNavPtr(fg: *FuncGen, inst: Air.Inst.Index) !Builder.Value {
         const o = fg.ng.object;
         const ty_nav = fg.air.instructions.items(.data)[@intFromEnum(inst)].ty_nav;
         const llvm_ptr_const = try o.lowerNavRefValue(ty_nav.nav);