Merge pull request #22230 from alexrp/lto-stuff

Disable LTO by default + some LTO fixes

7 files changed, 90 insertions, 69 deletions

diff --git a/src/Compilation.zig b/src/Compilation.zig
index 1a056c1c04..75b7f5e602 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -1881,18 +1881,6 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
                 comp.remaining_prelink_tasks += 1;
             }
 
-            if (target.isMinGW() and comp.config.any_non_single_threaded) {
-                // LLD might drop some symbols as unused during LTO and GCing, therefore,
-                // we force mark them for resolution here.
-
-                const tls_index_sym = switch (target.cpu.arch) {
-                    .x86 => "__tls_index",
-                    else => "_tls_index",
-                };
-
-                try comp.force_undefined_symbols.put(comp.gpa, tls_index_sym, {});
-            }
-
             if (comp.include_compiler_rt and capable_of_building_compiler_rt) {
                 if (is_exe_or_dyn_lib) {
                     log.debug("queuing a job to build compiler_rt_lib", .{});
@@ -3695,15 +3683,19 @@ fn performAllTheWorkInner(
     // In case it failed last time, try again. `clearMiscFailures` was already
     // called at the start of `update`.
     if (comp.queued_jobs.compiler_rt_lib and comp.compiler_rt_lib == null) {
-        comp.link_task_wait_group.spawnManager(buildRt, .{ comp, "compiler_rt.zig", .compiler_rt, .Lib, &comp.compiler_rt_lib, main_progress_node });
+        // LLVM disables LTO for its compiler-rt and we've had various issues with LTO of our
+        // compiler-rt due to LLD bugs as well, e.g.:
+        //
+        // https://github.com/llvm/llvm-project/issues/43698#issuecomment-2542660611
+        comp.link_task_wait_group.spawnManager(buildRt, .{ comp, "compiler_rt.zig", .compiler_rt, .Lib, false, &comp.compiler_rt_lib, main_progress_node });
     }
 
     if (comp.queued_jobs.compiler_rt_obj and comp.compiler_rt_obj == null) {
-        comp.link_task_wait_group.spawnManager(buildRt, .{ comp, "compiler_rt.zig", .compiler_rt, .Obj, &comp.compiler_rt_obj, main_progress_node });
+        comp.link_task_wait_group.spawnManager(buildRt, .{ comp, "compiler_rt.zig", .compiler_rt, .Obj, false, &comp.compiler_rt_obj, main_progress_node });
     }
 
     if (comp.queued_jobs.fuzzer_lib and comp.fuzzer_lib == null) {
-        comp.link_task_wait_group.spawnManager(buildRt, .{ comp, "fuzzer.zig", .libfuzzer, .Lib, &comp.fuzzer_lib, main_progress_node });
+        comp.link_task_wait_group.spawnManager(buildRt, .{ comp, "fuzzer.zig", .libfuzzer, .Lib, true, &comp.fuzzer_lib, main_progress_node });
     }
 
     if (comp.queued_jobs.glibc_shared_objects) {
@@ -4635,12 +4627,14 @@ fn buildRt(
     root_source_name: []const u8,
     misc_task: MiscTask,
     output_mode: std.builtin.OutputMode,
+    allow_lto: bool,
     out: *?CrtFile,
     prog_node: std.Progress.Node,
 ) void {
     comp.buildOutputFromZig(
         root_source_name,
         output_mode,
+        allow_lto,
         out,
         misc_task,
         prog_node,
@@ -4748,6 +4742,7 @@ fn buildZigLibc(comp: *Compilation, prog_node: std.Progress.Node) void {
     comp.buildOutputFromZig(
         "c.zig",
         .Lib,
+        true,
         &comp.libc_static_lib,
         .zig_libc,
         prog_node,
@@ -6453,6 +6448,7 @@ fn buildOutputFromZig(
     comp: *Compilation,
     src_basename: []const u8,
     output_mode: std.builtin.OutputMode,
+    allow_lto: bool,
     out: *?CrtFile,
     misc_task_tag: MiscTask,
     prog_node: std.Progress.Node,
@@ -6481,6 +6477,7 @@ fn buildOutputFromZig(
         .root_strip = strip,
         .link_libc = comp.config.link_libc,
         .any_unwind_tables = comp.root_mod.unwind_tables != .none,
+        .lto = if (allow_lto) comp.config.lto else .none,
     });
 
     const root_mod = try Package.Module.create(arena, .{
@@ -6581,6 +6578,8 @@ pub const CrtFileOptions = struct {
     unwind_tables: ?std.builtin.UnwindTables = null,
     pic: ?bool = null,
     no_builtin: ?bool = null,
+
+    allow_lto: bool = true,
 };
 
 pub fn build_crt_file(
@@ -6619,7 +6618,7 @@ pub fn build_crt_file(
         .link_libc = false,
         .any_unwind_tables = options.unwind_tables != .none,
         .lto = switch (output_mode) {
-            .Lib => comp.config.lto,
+            .Lib => if (options.allow_lto) comp.config.lto else .none,
             .Obj, .Exe => .none,
         },
     });
diff --git a/src/Compilation/Config.zig b/src/Compilation/Config.zig
index 41a8077203..ee175cce11 100644
--- a/src/Compilation/Config.zig
+++ b/src/Compilation/Config.zig
@@ -295,27 +295,8 @@ pub fn resolve(options: Options) ResolveError!Config {
         }
 
         if (options.lto) |x| break :b x;
-        if (!options.any_c_source_files) break :b .none;
-
-        // https://github.com/llvm/llvm-project/pull/116537
-        switch (target.abi) {
-            .gnuabin32,
-            .gnuilp32,
-            .gnux32,
-            .ilp32,
-            .muslabin32,
-            .muslx32,
-            => break :b .none,
-            else => {},
-        }
 
-        break :b switch (options.output_mode) {
-            .Lib, .Obj => .none,
-            .Exe => switch (root_optimize_mode) {
-                .Debug => .none,
-                .ReleaseSafe, .ReleaseFast, .ReleaseSmall => .full,
-            },
-        };
+        break :b .none;
     };
 
     const link_libcpp = b: {
diff --git a/src/libtsan.zig b/src/libtsan.zig
index 8b2427df1b..cd28b8694a 100644
--- a/src/libtsan.zig
+++ b/src/libtsan.zig
@@ -53,6 +53,8 @@ pub fn buildTsan(comp: *Compilation, prog_node: std.Progress.Node) BuildError!vo
     const optimize_mode = comp.compilerRtOptMode();
     const strip = comp.compilerRtStrip();
     const link_libcpp = target.isDarwin();
+    const unwind_tables: std.builtin.UnwindTables =
+        if (target.cpu.arch == .x86 and target.os.tag == .windows) .none else .@"async";
 
     const config = Compilation.Config.resolve(.{
         .output_mode = output_mode,
@@ -65,6 +67,9 @@ pub fn buildTsan(comp: *Compilation, prog_node: std.Progress.Node) BuildError!vo
         .root_strip = strip,
         .link_libc = true,
         .link_libcpp = link_libcpp,
+        .any_unwind_tables = unwind_tables != .none,
+        // LLVM disables LTO for its libtsan.
+        .lto = .none,
     }) catch |err| {
         comp.setMiscFailure(
             .libtsan,
@@ -95,6 +100,7 @@ pub fn buildTsan(comp: *Compilation, prog_node: std.Progress.Node) BuildError!vo
             .red_zone = comp.root_mod.red_zone,
             .omit_frame_pointer = optimize_mode != .Debug and !target.os.tag.isDarwin(),
             .valgrind = false,
+            .unwind_tables = unwind_tables,
             .optimize_mode = optimize_mode,
             .structured_cfg = comp.root_mod.structured_cfg,
             .pic = true,
diff --git a/src/link/Coff.zig b/src/link/Coff.zig
index 9bd3bd76e9..3b239246ca 100644
--- a/src/link/Coff.zig
+++ b/src/link/Coff.zig
@@ -1876,6 +1876,13 @@ fn linkWithLLD(coff: *Coff, arena: Allocator, tid: Zcu.PerThread.Id, prog_node:
         if (comp.version) |version| {
             try argv.append(try allocPrint(arena, "-VERSION:{}.{}", .{ version.major, version.minor }));
         }
+
+        if (target_util.llvmMachineAbi(target)) |mabi| {
+            try argv.append(try allocPrint(arena, "-MLLVM:-target-abi={s}", .{mabi}));
+        }
+
+        try argv.append(try allocPrint(arena, "-MLLVM:-float-abi={s}", .{if (target.abi.floatAbi() == .hard) "hard" else "soft"}));
+
         if (comp.config.lto != .none) {
             switch (optimize_mode) {
                 .Debug => {},
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index ea2fa56a5d..edd45f65ee 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -1700,6 +1700,18 @@ fn linkWithLLD(self: *Elf, arena: Allocator, tid: Zcu.PerThread.Id, prog_node: s
             try argv.append(try std.fmt.allocPrint(arena, "--sysroot={s}", .{sysroot}));
         }
 
+        if (target_util.llvmMachineAbi(target)) |mabi| {
+            try argv.appendSlice(&.{
+                "-mllvm",
+                try std.fmt.allocPrint(arena, "-target-abi={s}", .{mabi}),
+            });
+        }
+
+        try argv.appendSlice(&.{
+            "-mllvm",
+            try std.fmt.allocPrint(arena, "-float-abi={s}", .{if (target.abi.floatAbi() == .hard) "hard" else "soft"}),
+        });
+
         if (comp.config.lto != .none) {
             switch (comp.root_mod.optimize_mode) {
                 .Debug => {},
diff --git a/src/mingw.zig b/src/mingw.zig
index 47aff05133..17c0a49b11 100644
--- a/src/mingw.zig
+++ b/src/mingw.zig
@@ -175,6 +175,8 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
 
             return comp.build_crt_file("mingw32", .Lib, .@"mingw-w64 mingw32.lib", prog_node, c_source_files.items, .{
                 .unwind_tables = unwind_tables,
+                // https://github.com/llvm/llvm-project/issues/43698#issuecomment-2542660611
+                .allow_lto = false,
             });
         },
     }
diff --git a/src/target.zig b/src/target.zig
index 99e0fd1faa..546d10b0bc 100644
--- a/src/target.zig
+++ b/src/target.zig
@@ -482,16 +482,6 @@ pub fn arePointersLogical(target: std.Target, as: AddressSpace) bool {
 }
 
 pub fn llvmMachineAbi(target: std.Target) ?[:0]const u8 {
-    // This special-casing should be removed with LLVM 20.
-    switch (target.cpu.arch) {
-        .mips, .mipsel => return "o32",
-        .mips64, .mips64el => return switch (target.abi) {
-            .gnuabin32, .muslabin32 => "n32",
-            else => "n64",
-        },
-        else => {},
-    }
-
     // LLD does not support ELFv1. Rather than having LLVM produce ELFv1 code and then linking it
     // into a broken ELFv2 binary, just force LLVM to use ELFv2 as well. This will break when glibc
     // is linked as glibc only supports ELFv2 for little endian, but there's nothing we can do about
@@ -500,33 +490,57 @@ pub fn llvmMachineAbi(target: std.Target) ?[:0]const u8 {
     // Once our self-hosted linker can handle both ABIs, this hack should go away.
     if (target.cpu.arch == .powerpc64) return "elfv2";
 
-    switch (target.cpu.arch) {
-        .riscv64 => {
+    return switch (target.cpu.arch) {
+        .arm, .armeb, .thumb, .thumbeb => "aapcs",
+        // TODO: `muslsf` and `muslf32` in LLVM 20.
+        .loongarch64 => switch (target.abi) {
+            .gnusf => "lp64s",
+            .gnuf32 => "lp64f",
+            else => "lp64d",
+        },
+        .loongarch32 => switch (target.abi) {
+            .gnusf => "ilp32s",
+            .gnuf32 => "ilp32f",
+            else => "ilp32d",
+        },
+        .mips, .mipsel => "o32",
+        .mips64, .mips64el => switch (target.abi) {
+            .gnuabin32, .muslabin32 => "n32",
+            else => "n64",
+        },
+        .powerpc64 => switch (target.os.tag) {
+            .freebsd => if (target.os.version_range.semver.isAtLeast(.{ .major = 13, .minor = 0, .patch = 0 }) orelse false)
+                "elfv2"
+            else
+                "elfv1",
+            .openbsd => "elfv2",
+            else => if (target.abi.isMusl()) "elfv2" else "elfv1",
+        },
+        .powerpc64le => "elfv2",
+        .riscv64 => b: {
             const featureSetHas = std.Target.riscv.featureSetHas;
-            if (featureSetHas(target.cpu.features, .e)) {
-                return "lp64e";
-            } else if (featureSetHas(target.cpu.features, .d)) {
-                return "lp64d";
-            } else if (featureSetHas(target.cpu.features, .f)) {
-                return "lp64f";
-            } else {
-                return "lp64";
-            }
+            break :b if (featureSetHas(target.cpu.features, .e))
+                "lp64e"
+            else if (featureSetHas(target.cpu.features, .d))
+                "lp64d"
+            else if (featureSetHas(target.cpu.features, .f))
+                "lp64f"
+            else
+                "lp64";
         },
-        .riscv32 => {
+        .riscv32 => b: {
             const featureSetHas = std.Target.riscv.featureSetHas;
-            if (featureSetHas(target.cpu.features, .e)) {
-                return "ilp32e";
-            } else if (featureSetHas(target.cpu.features, .d)) {
-                return "ilp32d";
-            } else if (featureSetHas(target.cpu.features, .f)) {
-                return "ilp32f";
-            } else {
-                return "ilp32";
-            }
+            break :b if (featureSetHas(target.cpu.features, .e))
+                "ilp32e"
+            else if (featureSetHas(target.cpu.features, .d))
+                "ilp32d"
+            else if (featureSetHas(target.cpu.features, .f))
+                "ilp32f"
+            else
+                "ilp32";
         },
-        else => return null,
-    }
+        else => null,
+    };
 }
 
 /// This function returns 1 if function alignment is not observable or settable. Note that this