diff --git a/build.zig b/build.zig
index d53d823868..1ee8a21bda 100644
--- a/build.zig
+++ b/build.zig
@@ -19,7 +19,7 @@ pub fn build(b: *Builder) !void {
     const single_threaded = b.option(bool, "single-threaded", "Build artifacts that run in single threaded mode");
     const use_zig_libcxx = b.option(bool, "use-zig-libcxx", "If libc++ is needed, use zig's bundled version, don't try to integrate with the system") orelse false;
 
-    var docgen_exe = b.addExecutable("docgen", "doc/docgen.zig");
+    const docgen_exe = b.addExecutable("docgen", "doc/docgen.zig");
     docgen_exe.single_threaded = single_threaded;
 
     const rel_zig_exe = try fs.path.relative(b.allocator, b.build_root, b.zig_exe);
@@ -27,7 +27,7 @@ pub fn build(b: *Builder) !void {
         b.allocator,
         &[_][]const u8{ b.cache_root, "langref.html" },
     ) catch unreachable;
-    var docgen_cmd = docgen_exe.run();
+    const docgen_cmd = docgen_exe.run();
     docgen_cmd.addArgs(&[_][]const u8{
         rel_zig_exe,
         "doc" ++ fs.path.sep_str ++ "langref.html.in",
@@ -60,6 +60,7 @@ pub fn build(b: *Builder) !void {
     const skip_install_lib_files = b.option(bool, "skip-install-lib-files", "Do not copy lib/ files to installation prefix") orelse false;
 
     const only_install_lib_files = b.option(bool, "lib-files-only", "Only install library files") orelse false;
+
     const is_stage1 = b.option(bool, "stage1", "Build the stage1 compiler, put stage2 behind a feature flag") orelse false;
     const omit_stage2 = b.option(bool, "omit-stage2", "Do not include stage2 behind a feature flag inside stage1") orelse false;
     const static_llvm = b.option(bool, "static-llvm", "Disable integration with system-installed LLVM, Clang, LLD, and libc++") orelse false;
@@ -135,9 +136,9 @@ pub fn build(b: *Builder) !void {
         break :blk 4;
     };
 
-    const main_file = if (is_stage1) "src/stage1.zig" else "src/main.zig";
+    const main_file: ?[]const u8 = if (is_stage1) null else "src/main.zig";
 
-    var exe = b.addExecutable("zig", main_file);
+    const exe = b.addExecutable("zig", main_file);
     exe.strip = strip;
     exe.install();
     exe.setBuildMode(mode);
@@ -145,6 +146,7 @@ pub fn build(b: *Builder) !void {
     if (!skip_stage2_tests) {
         toolchain_step.dependOn(&exe.step);
     }
+
     b.default_step.dependOn(&exe.step);
     exe.single_threaded = single_threaded;
 
@@ -166,56 +168,6 @@ pub fn build(b: *Builder) !void {
     exe_options.addOption(bool, "llvm_has_arc", llvm_has_arc);
     exe_options.addOption(bool, "force_gpa", force_gpa);
 
-    if (enable_llvm) {
-        const cmake_cfg = if (static_llvm) null else findAndParseConfigH(b, config_h_path_option);
-
-        if (is_stage1) {
-            exe.addIncludePath("src");
-            exe.addIncludePath("deps/SoftFloat-3e/source/include");
-
-            test_stage2.addIncludePath("src");
-            test_stage2.addIncludePath("deps/SoftFloat-3e/source/include");
-            // This is intentionally a dummy path. stage1.zig tries to @import("compiler_rt") in case
-            // of being built by cmake. But when built by zig it's gonna get a compiler_rt so that
-            // is pointless.
-            exe.addPackagePath("compiler_rt", "src/empty.zig");
-            exe.defineCMacro("ZIG_LINK_MODE", "Static");
-            test_stage2.defineCMacro("ZIG_LINK_MODE", "Static");
-
-            const softfloat = b.addStaticLibrary("softfloat", null);
-            softfloat.setBuildMode(.ReleaseFast);
-            softfloat.setTarget(target);
-            softfloat.addIncludePath("deps/SoftFloat-3e-prebuilt");
-            softfloat.addIncludePath("deps/SoftFloat-3e/source/8086");
-            softfloat.addIncludePath("deps/SoftFloat-3e/source/include");
-            softfloat.addCSourceFiles(&softfloat_sources, &[_][]const u8{ "-std=c99", "-O3" });
-            softfloat.single_threaded = single_threaded;
-
-            exe.linkLibrary(softfloat);
-            test_stage2.linkLibrary(softfloat);
-
-            exe.addCSourceFiles(&stage1_sources, &exe_cflags);
-            exe.addCSourceFiles(&optimized_c_sources, &[_][]const u8{ "-std=c99", "-O3" });
-
-            test_stage2.addCSourceFiles(&stage1_sources, &exe_cflags);
-            test_stage2.addCSourceFiles(&optimized_c_sources, &[_][]const u8{ "-std=c99", "-O3" });
-        }
-        if (cmake_cfg) |cfg| {
-            // Inside this code path, we have to coordinate with system packaged LLVM, Clang, and LLD.
-            // That means we also have to rely on stage1 compiled c++ files. We parse config.h to find
-            // the information passed on to us from cmake.
-            if (cfg.cmake_prefix_path.len > 0) {
-                b.addSearchPrefix(cfg.cmake_prefix_path);
-            }
-
-            try addCmakeCfgOptionsToExe(b, cfg, exe, use_zig_libcxx);
-            try addCmakeCfgOptionsToExe(b, cfg, test_stage2, use_zig_libcxx);
-        } else {
-            // Here we are -Denable-llvm but no cmake integration.
-            try addStaticLlvmOptionsToExe(exe);
-            try addStaticLlvmOptionsToExe(test_stage2);
-        }
-    }
     if (link_libc) {
         exe.linkLibC();
         test_stage2.linkLibC();
@@ -227,12 +179,12 @@ pub fn build(b: *Builder) !void {
 
     const opt_version_string = b.option([]const u8, "version-string", "Override Zig version string. Default is to find out with git.");
     const version = if (opt_version_string) |version| version else v: {
-        const version_string = b.fmt("{d}.{d}.{d}", .{ zig_version.major, zig_version.minor, zig_version.patch });
-
         if (!std.process.can_spawn) {
             std.debug.print("error: version info cannot be retrieved from git. Zig version must be provided using -Dversion-string\n", .{});
             std.process.exit(1);
         }
+        const version_string = b.fmt("{d}.{d}.{d}", .{ zig_version.major, zig_version.minor, zig_version.patch });
+
         var code: u8 = undefined;
         const git_describe_untrimmed = b.execAllowFail(&[_][]const u8{
             "git", "-C", b.build_root, "describe", "--match", "*.*.*", "--tags",
@@ -280,6 +232,108 @@ pub fn build(b: *Builder) !void {
     };
     exe_options.addOption([:0]const u8, "version", try b.allocator.dupeZ(u8, version));
 
+    if (enable_llvm) {
+        const cmake_cfg = if (static_llvm) null else findAndParseConfigH(b, config_h_path_option);
+
+        if (is_stage1) {
+            const softfloat = b.addStaticLibrary("softfloat", null);
+            softfloat.setBuildMode(.ReleaseFast);
+            softfloat.setTarget(target);
+            softfloat.addIncludePath("deps/SoftFloat-3e-prebuilt");
+            softfloat.addIncludePath("deps/SoftFloat-3e/source/8086");
+            softfloat.addIncludePath("deps/SoftFloat-3e/source/include");
+            softfloat.addCSourceFiles(&softfloat_sources, &[_][]const u8{ "-std=c99", "-O3" });
+            softfloat.single_threaded = single_threaded;
+
+            const zig0 = b.addExecutable("zig0", null);
+            zig0.addCSourceFiles(&.{"src/stage1/zig0.cpp"}, &exe_cflags);
+            zig0.addIncludePath("zig-cache/tmp"); // for config.h
+            zig0.defineCMacro("ZIG_VERSION_MAJOR", b.fmt("{d}", .{zig_version.major}));
+            zig0.defineCMacro("ZIG_VERSION_MINOR", b.fmt("{d}", .{zig_version.minor}));
+            zig0.defineCMacro("ZIG_VERSION_PATCH", b.fmt("{d}", .{zig_version.patch}));
+            zig0.defineCMacro("ZIG_VERSION_STRING", b.fmt("\"{s}\"", .{version}));
+
+            for ([_]*std.build.LibExeObjStep{ zig0, exe }) |artifact| {
+                artifact.addIncludePath("src");
+                artifact.addIncludePath("deps/SoftFloat-3e/source/include");
+                artifact.addIncludePath("deps/SoftFloat-3e-prebuilt");
+
+                artifact.defineCMacro("ZIG_LINK_MODE", "Static");
+
+                artifact.addCSourceFiles(&stage1_sources, &exe_cflags);
+                artifact.addCSourceFiles(&optimized_c_sources, &[_][]const u8{ "-std=c99", "-O3" });
+
+                artifact.linkLibrary(softfloat);
+                artifact.linkLibCpp();
+            }
+
+            try addStaticLlvmOptionsToExe(zig0);
+
+            const zig1_obj_ext = target.getObjectFormat().fileExt(target.getCpuArch());
+            const zig1_obj_path = b.pathJoin(&.{ "zig-cache", "tmp", b.fmt("zig1{s}", .{zig1_obj_ext}) });
+            const zig1_compiler_rt_path = b.pathJoin(&.{ b.pathFromRoot("lib"), "std", "special", "compiler_rt.zig" });
+
+            const zig1_obj = zig0.run();
+            zig1_obj.addArgs(&.{
+                "src/stage1.zig",
+                "-target",
+                try target.zigTriple(b.allocator),
+                "-mcpu=baseline",
+                "--name",
+                "zig1",
+                "--zig-lib-dir",
+                b.pathFromRoot("lib"),
+                b.fmt("-femit-bin={s}", .{b.pathFromRoot(zig1_obj_path)}),
+                "-fcompiler-rt",
+                "-lc",
+            });
+            {
+                zig1_obj.addArgs(&.{ "--pkg-begin", "build_options" });
+                zig1_obj.addFileSourceArg(exe_options.getSource());
+                zig1_obj.addArgs(&.{ "--pkg-end", "--pkg-begin", "compiler_rt", zig1_compiler_rt_path, "--pkg-end" });
+            }
+            switch (mode) {
+                .Debug => {},
+                .ReleaseFast => {
+                    zig1_obj.addArg("-OReleaseFast");
+                    zig1_obj.addArg("--strip");
+                },
+                .ReleaseSafe => {
+                    zig1_obj.addArg("-OReleaseSafe");
+                    zig1_obj.addArg("--strip");
+                },
+                .ReleaseSmall => {
+                    zig1_obj.addArg("-OReleaseSmall");
+                    zig1_obj.addArg("--strip");
+                },
+            }
+            if (single_threaded orelse false) {
+                zig1_obj.addArg("-fsingle-threaded");
+            }
+
+            exe.step.dependOn(&zig1_obj.step);
+            exe.addObjectFile(zig1_obj_path);
+
+            // This is intentionally a dummy path. stage1.zig tries to @import("compiler_rt") in case
+            // of being built by cmake. But when built by zig it's gonna get a compiler_rt so that
+            // is pointless.
+            exe.addPackagePath("compiler_rt", "src/empty.zig");
+        }
+        if (cmake_cfg) |cfg| {
+            // Inside this code path, we have to coordinate with system packaged LLVM, Clang, and LLD.
+            // That means we also have to rely on stage1 compiled c++ files. We parse config.h to find
+            // the information passed on to us from cmake.
+            if (cfg.cmake_prefix_path.len > 0) {
+                b.addSearchPrefix(cfg.cmake_prefix_path);
+            }
+
+            try addCmakeCfgOptionsToExe(b, cfg, exe, use_zig_libcxx);
+        } else {
+            // Here we are -Denable-llvm but no cmake integration.
+            try addStaticLlvmOptionsToExe(exe);
+        }
+    }
+
     const semver = try std.SemanticVersion.parse(version);
     exe_options.addOption(std.SemanticVersion, "semver", semver);
 
@@ -548,7 +602,6 @@ fn addCxxKnownPath(
 ) !void {
     if (!std.process.can_spawn)
         return error.RequiredLibraryNotFound;
-
     const path_padded = try b.exec(&[_][]const u8{
         ctx.cxx_compiler,
         b.fmt("-print-file-name={s}", .{objname}),
@@ -695,15 +748,19 @@ fn toNativePathSep(b: *Builder, s: []const u8) []u8 {
 
 const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/8086/f128M_isSignalingNaN.c",
+    "deps/SoftFloat-3e/source/8086/extF80M_isSignalingNaN.c",
     "deps/SoftFloat-3e/source/8086/s_commonNaNToF128M.c",
+    "deps/SoftFloat-3e/source/8086/s_commonNaNToExtF80M.c",
     "deps/SoftFloat-3e/source/8086/s_commonNaNToF16UI.c",
     "deps/SoftFloat-3e/source/8086/s_commonNaNToF32UI.c",
     "deps/SoftFloat-3e/source/8086/s_commonNaNToF64UI.c",
     "deps/SoftFloat-3e/source/8086/s_f128MToCommonNaN.c",
+    "deps/SoftFloat-3e/source/8086/s_extF80MToCommonNaN.c",
     "deps/SoftFloat-3e/source/8086/s_f16UIToCommonNaN.c",
     "deps/SoftFloat-3e/source/8086/s_f32UIToCommonNaN.c",
     "deps/SoftFloat-3e/source/8086/s_f64UIToCommonNaN.c",
     "deps/SoftFloat-3e/source/8086/s_propagateNaNF128M.c",
+    "deps/SoftFloat-3e/source/8086/s_propagateNaNExtF80M.c",
     "deps/SoftFloat-3e/source/8086/s_propagateNaNF16UI.c",
     "deps/SoftFloat-3e/source/8086/softfloat_raiseFlags.c",
     "deps/SoftFloat-3e/source/f128M_add.c",
@@ -723,6 +780,7 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/f128M_to_f16.c",
     "deps/SoftFloat-3e/source/f128M_to_f32.c",
     "deps/SoftFloat-3e/source/f128M_to_f64.c",
+    "deps/SoftFloat-3e/source/f128M_to_extF80M.c",
     "deps/SoftFloat-3e/source/f128M_to_i32.c",
     "deps/SoftFloat-3e/source/f128M_to_i32_r_minMag.c",
     "deps/SoftFloat-3e/source/f128M_to_i64.c",
@@ -731,6 +789,20 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/f128M_to_ui32_r_minMag.c",
     "deps/SoftFloat-3e/source/f128M_to_ui64.c",
     "deps/SoftFloat-3e/source/f128M_to_ui64_r_minMag.c",
+    "deps/SoftFloat-3e/source/extF80M_add.c",
+    "deps/SoftFloat-3e/source/extF80M_div.c",
+    "deps/SoftFloat-3e/source/extF80M_eq.c",
+    "deps/SoftFloat-3e/source/extF80M_le.c",
+    "deps/SoftFloat-3e/source/extF80M_lt.c",
+    "deps/SoftFloat-3e/source/extF80M_mul.c",
+    "deps/SoftFloat-3e/source/extF80M_rem.c",
+    "deps/SoftFloat-3e/source/extF80M_roundToInt.c",
+    "deps/SoftFloat-3e/source/extF80M_sqrt.c",
+    "deps/SoftFloat-3e/source/extF80M_sub.c",
+    "deps/SoftFloat-3e/source/extF80M_to_f16.c",
+    "deps/SoftFloat-3e/source/extF80M_to_f32.c",
+    "deps/SoftFloat-3e/source/extF80M_to_f64.c",
+    "deps/SoftFloat-3e/source/extF80M_to_f128M.c",
     "deps/SoftFloat-3e/source/f16_add.c",
     "deps/SoftFloat-3e/source/f16_div.c",
     "deps/SoftFloat-3e/source/f16_eq.c",
@@ -742,9 +814,12 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/f16_roundToInt.c",
     "deps/SoftFloat-3e/source/f16_sqrt.c",
     "deps/SoftFloat-3e/source/f16_sub.c",
+    "deps/SoftFloat-3e/source/f16_to_extF80M.c",
     "deps/SoftFloat-3e/source/f16_to_f128M.c",
     "deps/SoftFloat-3e/source/f16_to_f64.c",
+    "deps/SoftFloat-3e/source/f32_to_extF80M.c",
     "deps/SoftFloat-3e/source/f32_to_f128M.c",
+    "deps/SoftFloat-3e/source/f64_to_extF80M.c",
     "deps/SoftFloat-3e/source/f64_to_f128M.c",
     "deps/SoftFloat-3e/source/f64_to_f16.c",
     "deps/SoftFloat-3e/source/i32_to_f128M.c",
@@ -752,6 +827,7 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/s_addCarryM.c",
     "deps/SoftFloat-3e/source/s_addComplCarryM.c",
     "deps/SoftFloat-3e/source/s_addF128M.c",
+    "deps/SoftFloat-3e/source/s_addExtF80M.c",
     "deps/SoftFloat-3e/source/s_addM.c",
     "deps/SoftFloat-3e/source/s_addMagsF16.c",
     "deps/SoftFloat-3e/source/s_addMagsF32.c",
@@ -762,12 +838,14 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/s_approxRecip_1Ks.c",
     "deps/SoftFloat-3e/source/s_compare128M.c",
     "deps/SoftFloat-3e/source/s_compare96M.c",
+    "deps/SoftFloat-3e/source/s_compareNonnormExtF80M.c",
     "deps/SoftFloat-3e/source/s_countLeadingZeros16.c",
     "deps/SoftFloat-3e/source/s_countLeadingZeros32.c",
     "deps/SoftFloat-3e/source/s_countLeadingZeros64.c",
     "deps/SoftFloat-3e/source/s_countLeadingZeros8.c",
     "deps/SoftFloat-3e/source/s_eq128.c",
     "deps/SoftFloat-3e/source/s_invalidF128M.c",
+    "deps/SoftFloat-3e/source/s_invalidExtF80M.c",
     "deps/SoftFloat-3e/source/s_isNaNF128M.c",
     "deps/SoftFloat-3e/source/s_le128.c",
     "deps/SoftFloat-3e/source/s_lt128.c",
@@ -778,7 +856,9 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/s_mulAddF32.c",
     "deps/SoftFloat-3e/source/s_mulAddF64.c",
     "deps/SoftFloat-3e/source/s_negXM.c",
+    "deps/SoftFloat-3e/source/s_normExtF80SigM.c",
     "deps/SoftFloat-3e/source/s_normRoundPackMToF128M.c",
+    "deps/SoftFloat-3e/source/s_normRoundPackMToExtF80M.c",
     "deps/SoftFloat-3e/source/s_normRoundPackToF16.c",
     "deps/SoftFloat-3e/source/s_normRoundPackToF32.c",
     "deps/SoftFloat-3e/source/s_normRoundPackToF64.c",
@@ -789,6 +869,7 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/s_remStepMBy32.c",
     "deps/SoftFloat-3e/source/s_roundMToI64.c",
     "deps/SoftFloat-3e/source/s_roundMToUI64.c",
+    "deps/SoftFloat-3e/source/s_roundPackMToExtF80M.c",
     "deps/SoftFloat-3e/source/s_roundPackMToF128M.c",
     "deps/SoftFloat-3e/source/s_roundPackToF16.c",
     "deps/SoftFloat-3e/source/s_roundPackToF32.c",
@@ -817,9 +898,12 @@ const softfloat_sources = [_][]const u8{
     "deps/SoftFloat-3e/source/s_subMagsF32.c",
     "deps/SoftFloat-3e/source/s_subMagsF64.c",
     "deps/SoftFloat-3e/source/s_tryPropagateNaNF128M.c",
+    "deps/SoftFloat-3e/source/s_tryPropagateNaNExtF80M.c",
     "deps/SoftFloat-3e/source/softfloat_state.c",
     "deps/SoftFloat-3e/source/ui32_to_f128M.c",
     "deps/SoftFloat-3e/source/ui64_to_f128M.c",
+    "deps/SoftFloat-3e/source/ui32_to_extF80M.c",
+    "deps/SoftFloat-3e/source/ui64_to_extF80M.c",
 };
 
 const stage1_sources = [_][]const u8{