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build: add -Donly-c option
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This option can be used to produce a C backend build of the self-hosted
compiler, which only has the C backend enabled. Once the C backend is
capable of self-hosting, this will be a way for us to replace our stage1
codebase with a C backend build of self-hosted, which we can then use
for bootstrapping. See #5246 for more details.

Using this option right now results in a crash because the C backend is
not yet passing all the behavior tests.
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@andrewrk
andrewrk committed Oct 23, 2022
1 parent 828735a commit 9148be4
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Showing 3 changed files with 91 additions and 14 deletions.
10 changes: 9 additions & 1 deletion build.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,8 @@ pub fn build(b: *Builder) !void {

const fmt_build_zig = b.addFmt(&[_][]const u8{"build.zig"});

const only_c = b.option(bool, "only-c", "Translate the Zig compiler to C code, with only the C backend enabled") orelse false;

const skip_debug = b.option(bool, "skip-debug", "Main test suite skips debug builds") orelse false;
const skip_release = b.option(bool, "skip-release", "Main test suite skips release builds") orelse false;
const skip_release_small = b.option(bool, "skip-release-small", "Main test suite skips release-small builds") orelse skip_release;
Expand Down Expand Up @@ -123,7 +125,7 @@ pub fn build(b: *Builder) !void {
const tracy_callstack = b.option(bool, "tracy-callstack", "Include callstack information with Tracy data. Does nothing if -Dtracy is not provided") orelse false;
const tracy_allocation = b.option(bool, "tracy-allocation", "Include allocation information with Tracy data. Does nothing if -Dtracy is not provided") orelse false;
const force_gpa = b.option(bool, "force-gpa", "Force the compiler to use GeneralPurposeAllocator") orelse false;
const link_libc = b.option(bool, "force-link-libc", "Force self-hosted compiler to link libc") orelse enable_llvm;
const link_libc = b.option(bool, "force-link-libc", "Force self-hosted compiler to link libc") orelse (enable_llvm or only_c);
const sanitize_thread = b.option(bool, "sanitize-thread", "Enable thread-sanitization") orelse false;
const strip = b.option(bool, "strip", "Omit debug information") orelse false;
const use_zig0 = b.option(bool, "zig0", "Bootstrap using zig0") orelse false;
Expand Down Expand Up @@ -166,6 +168,10 @@ pub fn build(b: *Builder) !void {
test_cases.want_lto = false;
}

if (only_c) {
exe.ofmt = .c;
}

const exe_options = b.addOptions();
exe.addOptions("build_options", exe_options);

Expand All @@ -176,6 +182,7 @@ pub fn build(b: *Builder) !void {
exe_options.addOption(bool, "llvm_has_csky", llvm_has_csky);
exe_options.addOption(bool, "llvm_has_arc", llvm_has_arc);
exe_options.addOption(bool, "force_gpa", force_gpa);
exe_options.addOption(bool, "only_c", only_c);

if (link_libc) {
exe.linkLibC();
Expand Down Expand Up @@ -408,6 +415,7 @@ pub fn build(b: *Builder) !void {
test_cases_options.addOption(bool, "llvm_has_csky", llvm_has_csky);
test_cases_options.addOption(bool, "llvm_has_arc", llvm_has_arc);
test_cases_options.addOption(bool, "force_gpa", force_gpa);
test_cases_options.addOption(bool, "only_c", only_c);
test_cases_options.addOption(bool, "enable_qemu", b.enable_qemu);
test_cases_options.addOption(bool, "enable_wine", b.enable_wine);
test_cases_options.addOption(bool, "enable_wasmtime", b.enable_wasmtime);
Expand Down
1 change: 1 addition & 0 deletions src/config.zig.in
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,3 +10,4 @@ pub const enable_tracy = false;
pub const value_tracing = false;
pub const have_stage1 = true;
pub const skip_non_native = false;
pub const only_c = false;
94 changes: 81 additions & 13 deletions src/link.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -284,7 +284,8 @@ pub const File = struct {
/// rewriting it. A malicious file is detected as incremental link failure
/// and does not cause Illegal Behavior. This operation is not atomic.
pub fn openPath(allocator: Allocator, options: Options) !*File {
if (options.target.ofmt == .macho) {
const have_macho = !build_options.only_c;
if (have_macho and options.target.ofmt == .macho) {
return &(try MachO.openPath(allocator, options)).base;
}

Expand Down Expand Up @@ -332,18 +333,40 @@ pub const File = struct {
} else emit.sub_path;
errdefer if (use_lld) allocator.free(sub_path);

const file: *File = switch (options.target.ofmt) {
.coff => &(try Coff.openPath(allocator, sub_path, options)).base,
.elf => &(try Elf.openPath(allocator, sub_path, options)).base,
.macho => unreachable,
.plan9 => &(try Plan9.openPath(allocator, sub_path, options)).base,
.wasm => &(try Wasm.openPath(allocator, sub_path, options)).base,
.c => &(try C.openPath(allocator, sub_path, options)).base,
.spirv => &(try SpirV.openPath(allocator, sub_path, options)).base,
.nvptx => &(try NvPtx.openPath(allocator, sub_path, options)).base,
.hex => return error.HexObjectFormatUnimplemented,
.raw => return error.RawObjectFormatUnimplemented,
.dxcontainer => return error.DirectXContainerObjectFormatUnimplemented,
const file: *File = f: {
switch (options.target.ofmt) {
.coff => {
if (build_options.only_c) unreachable;
break :f &(try Coff.openPath(allocator, sub_path, options)).base;
},
.elf => {
if (build_options.only_c) unreachable;
break :f &(try Elf.openPath(allocator, sub_path, options)).base;
},
.macho => unreachable,
.plan9 => {
if (build_options.only_c) unreachable;
break :f &(try Plan9.openPath(allocator, sub_path, options)).base;
},
.wasm => {
if (build_options.only_c) unreachable;
break :f &(try Wasm.openPath(allocator, sub_path, options)).base;
},
.c => {
break :f &(try C.openPath(allocator, sub_path, options)).base;
},
.spirv => {
if (build_options.only_c) unreachable;
break :f &(try SpirV.openPath(allocator, sub_path, options)).base;
},
.nvptx => {
if (build_options.only_c) unreachable;
break :f &(try NvPtx.openPath(allocator, sub_path, options)).base;
},
.hex => return error.HexObjectFormatUnimplemented,
.raw => return error.RawObjectFormatUnimplemented,
.dxcontainer => return error.DirectXContainerObjectFormatUnimplemented,
}
};

if (use_lld) {
Expand All @@ -366,6 +389,7 @@ pub const File = struct {
pub fn makeWritable(base: *File) !void {
switch (base.tag) {
.coff, .elf, .macho, .plan9, .wasm => {
if (build_options.only_c) unreachable;
if (base.file != null) return;
const emit = base.options.emit orelse return;
base.file = try emit.directory.handle.createFile(emit.sub_path, .{
Expand All @@ -389,6 +413,7 @@ pub const File = struct {
}
switch (base.tag) {
.macho => if (base.file) |f| {
if (build_options.only_c) unreachable;
if (comptime builtin.target.isDarwin() and builtin.target.cpu.arch == .aarch64) {
if (base.options.target.cpu.arch == .aarch64) {
// XNU starting with Big Sur running on arm64 is caching inodes of running binaries.
Expand All @@ -407,6 +432,7 @@ pub const File = struct {
base.file = null;
},
.coff, .elf, .plan9, .wasm => if (base.file) |f| {
if (build_options.only_c) unreachable;
if (base.intermediary_basename != null) {
// The file we have open is not the final file that we want to
// make executable, so we don't have to close it.
Expand Down Expand Up @@ -454,6 +480,7 @@ pub const File = struct {
/// constant. Returns the symbol index of the lowered constant in the read-only section
/// of the final binary.
pub fn lowerUnnamedConst(base: *File, tv: TypedValue, decl_index: Module.Decl.Index) UpdateDeclError!u32 {
if (build_options.only_c) @compileError("unreachable");
const decl = base.options.module.?.declPtr(decl_index);
log.debug("lowerUnnamedConst {*} ({s})", .{ decl, decl.name });
switch (base.tag) {
Expand All @@ -474,6 +501,7 @@ pub const File = struct {
/// If no symbol exists yet with this name, a new undefined global symbol will
/// be created. This symbol may get resolved once all relocatables are (re-)linked.
pub fn getGlobalSymbol(base: *File, name: []const u8) UpdateDeclError!u32 {
if (build_options.only_c) @compileError("unreachable");
log.debug("getGlobalSymbol '{s}'", .{name});
switch (base.tag) {
// zig fmt: off
Expand All @@ -495,6 +523,10 @@ pub const File = struct {
const decl = module.declPtr(decl_index);
log.debug("updateDecl {*} ({s}), type={}", .{ decl, decl.name, decl.ty.fmtDebug() });
assert(decl.has_tv);
if (build_options.only_c) {
assert(base.tag == .c);
return @fieldParentPtr(C, "base", base).updateDecl(module, decl_index);
}
switch (base.tag) {
// zig fmt: off
.coff => return @fieldParentPtr(Coff, "base", base).updateDecl(module, decl_index),
Expand All @@ -516,6 +548,10 @@ pub const File = struct {
log.debug("updateFunc {*} ({s}), type={}", .{
owner_decl, owner_decl.name, owner_decl.ty.fmtDebug(),
});
if (build_options.only_c) {
assert(base.tag == .c);
return @fieldParentPtr(C, "base", base).updateFunc(module, func, air, liveness);
}
switch (base.tag) {
// zig fmt: off
.coff => return @fieldParentPtr(Coff, "base", base).updateFunc(module, func, air, liveness),
Expand All @@ -535,6 +571,10 @@ pub const File = struct {
decl, decl.name, decl.src_line + 1,
});
assert(decl.has_tv);
if (build_options.only_c) {
assert(base.tag == .c);
return @fieldParentPtr(C, "base", base).updateDeclLineNumber(module, decl);
}
switch (base.tag) {
.coff => return @fieldParentPtr(Coff, "base", base).updateDeclLineNumber(module, decl),
.elf => return @fieldParentPtr(Elf, "base", base).updateDeclLineNumber(module, decl),
Expand All @@ -554,6 +594,10 @@ pub const File = struct {
pub fn allocateDeclIndexes(base: *File, decl_index: Module.Decl.Index) error{OutOfMemory}!void {
const decl = base.options.module.?.declPtr(decl_index);
log.debug("allocateDeclIndexes {*} ({s})", .{ decl, decl.name });
if (build_options.only_c) {
assert(base.tag == .c);
return;
}
switch (base.tag) {
.coff => return @fieldParentPtr(Coff, "base", base).allocateDeclIndexes(decl_index),
.elf => return @fieldParentPtr(Elf, "base", base).allocateDeclIndexes(decl_index),
Expand Down Expand Up @@ -584,16 +628,19 @@ pub const File = struct {
base.options.system_libs.deinit(base.allocator);
switch (base.tag) {
.coff => {
if (build_options.only_c) unreachable;
const parent = @fieldParentPtr(Coff, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.elf => {
if (build_options.only_c) unreachable;
const parent = @fieldParentPtr(Elf, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.macho => {
if (build_options.only_c) unreachable;
const parent = @fieldParentPtr(MachO, "base", base);
parent.deinit();
base.allocator.destroy(parent);
Expand All @@ -604,21 +651,25 @@ pub const File = struct {
base.allocator.destroy(parent);
},
.wasm => {
if (build_options.only_c) unreachable;
const parent = @fieldParentPtr(Wasm, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.spirv => {
if (build_options.only_c) unreachable;
const parent = @fieldParentPtr(SpirV, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.plan9 => {
if (build_options.only_c) unreachable;
const parent = @fieldParentPtr(Plan9, "base", base);
parent.deinit();
base.allocator.destroy(parent);
},
.nvptx => {
if (build_options.only_c) unreachable;
const parent = @fieldParentPtr(NvPtx, "base", base);
parent.deinit();
base.allocator.destroy(parent);
Expand All @@ -629,6 +680,10 @@ pub const File = struct {
/// Commit pending changes and write headers. Takes into account final output mode
/// and `use_lld`, not only `effectiveOutputMode`.
pub fn flush(base: *File, comp: *Compilation, prog_node: *std.Progress.Node) !void {
if (build_options.only_c) {
assert(base.tag == .c);
return @fieldParentPtr(C, "base", base).flush(comp, prog_node);
}
if (comp.clang_preprocessor_mode == .yes) {
const emit = base.options.emit orelse return; // -fno-emit-bin
// TODO: avoid extra link step when it's just 1 object file (the `zig cc -c` case)
Expand Down Expand Up @@ -663,6 +718,10 @@ pub const File = struct {
/// Commit pending changes and write headers. Works based on `effectiveOutputMode`
/// rather than final output mode.
pub fn flushModule(base: *File, comp: *Compilation, prog_node: *std.Progress.Node) !void {
if (build_options.only_c) {
assert(base.tag == .c);
return @fieldParentPtr(C, "base", base).flushModule(comp, prog_node);
}
switch (base.tag) {
.coff => return @fieldParentPtr(Coff, "base", base).flushModule(comp, prog_node),
.elf => return @fieldParentPtr(Elf, "base", base).flushModule(comp, prog_node),
Expand All @@ -677,6 +736,10 @@ pub const File = struct {

/// Called when a Decl is deleted from the Module.
pub fn freeDecl(base: *File, decl_index: Module.Decl.Index) void {
if (build_options.only_c) {
assert(base.tag == .c);
return @fieldParentPtr(C, "base", base).freeDecl(decl_index);
}
switch (base.tag) {
.coff => @fieldParentPtr(Coff, "base", base).freeDecl(decl_index),
.elf => @fieldParentPtr(Elf, "base", base).freeDecl(decl_index),
Expand Down Expand Up @@ -716,6 +779,10 @@ pub const File = struct {
const decl = module.declPtr(decl_index);
log.debug("updateDeclExports {*} ({s})", .{ decl, decl.name });
assert(decl.has_tv);
if (build_options.only_c) {
assert(base.tag == .c);
return @fieldParentPtr(C, "base", base).updateDeclExports(module, decl_index, exports);
}
switch (base.tag) {
.coff => return @fieldParentPtr(Coff, "base", base).updateDeclExports(module, decl_index, exports),
.elf => return @fieldParentPtr(Elf, "base", base).updateDeclExports(module, decl_index, exports),
Expand All @@ -739,6 +806,7 @@ pub const File = struct {
/// memory buffer, `offset`, so that it can make a note of potential relocation sites, should the
/// `Decl`'s address was not yet resolved, or the containing atom gets moved in virtual memory.
pub fn getDeclVAddr(base: *File, decl_index: Module.Decl.Index, reloc_info: RelocInfo) !u64 {
if (build_options.only_c) unreachable;
switch (base.tag) {
.coff => return @fieldParentPtr(Coff, "base", base).getDeclVAddr(decl_index, reloc_info),
.elf => return @fieldParentPtr(Elf, "base", base).getDeclVAddr(decl_index, reloc_info),
Expand Down

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