unable to build zig with x86 backend using ReleaseFast optimization mode

[andrewrk]

1b0b46a

$ ./zig2 build --zig-lib-dir lib -Doptimize=ReleaseFast -Dstrip -Dno-langref -Dno-autodocs
zig build-exe zig ReleaseFast native: error: error(x86_64_encoder): no encoding found for: none mov m128 r64 none none
error(x86_64_encoder): no encoding found for: none mov m128 r64 none none
error(x86_64_encoder): no encoding found for: none mov m128 r64 none none
error(x86_64_encoder): no encoding found for: none mov m128 r64 none none
error(x86_64_encoder): no encoding found for: none mov m256 r64 none none
error(x86_64_encoder): no encoding found for: none mov m128 r64 none none
error(x86_64_encoder): no encoding found for: none mov m128 r64 none none
error(x86_64_encoder): no encoding found for: none mov m128 r64 none none
error(x86_64_encoder): no encoding found for: none mov m128 r64 none none

zig build-exe zig ReleaseFast native: error: the following command failed with 9 compilation errors:
/home/andy/Downloads/zig/zig2 build-exe --stack 33554432 /home/andy/Downloads/zig/src/main.zig -fstrip -OReleaseFast --cache-dir /home/andy/Downloads/zig/zig-cache --global-cache-dir /home/andy/.cache/zig --name zig --mod aro::/home/andy/Downloads/zig/deps/aro/lib.zig --mod build_options::/home/andy/Downloads/zig/zig-cache/c/b0a3e19e067b3b3c4957215274d0ade5/options.zig --deps aro,build_options --zig-lib-dir /home/andy/Downloads/zig/lib --listen=- 
Build Summary: 2/5 steps succeeded; 1 failed (disable with --summary none)
install transitive failure
└─ install zig transitive failure
   └─ zig build-exe zig ReleaseFast native 9 errors
deps/aro/Attribute.zig:1281:1: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
fn applyAligned(attr: Attribute, p: *Parser, ty: Type, tag: ?Diagnostics.Tag) !void {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Parser.zig:224:1: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
fn validateExtendedIdentifier(p: *Parser) !bool {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Parser.zig:7617:1: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
fn parseNumberEscape(p: *Parser, tok: TokenIndex, base: u8, slice: []const u8, i: *usize) !u8 {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Parser.zig:7634:1: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
fn parseUnicodeEscape(p: *Parser, tok: TokenIndex, count: u8, slice: []const u8, i: *usize) !void {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Attribute.zig:922:5: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
pub fn initArguments(tag: Tag, name_tok: TokenIndex) Arguments {
~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Parser.zig:4240:1: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
fn labeledStmt(p: *Parser) Error!?NodeIndex {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Attribute.zig:223:5: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
pub fn diagnoseAlignment(attr: Tag, arguments: *Arguments, arg_idx: u32, val: Value, ty: Type, comp: *Compilation) ?Diagnostics.Message {
~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Parser.zig:358:1: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
fn errOverflow(p: *Parser, op_tok: TokenIndex, res: Result) !void {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
deps/aro/Parser.zig:7212:1: error: CodeGen failed to find a viable instruction. This is a bug in the Zig compiler.
fn checkArrayBounds(p: *Parser, index: Result, array: Result, tok: TokenIndex) !void {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

target CPU and OS info:

pub const cpu: std.Target.Cpu = .{
    .arch = .x86_64,
    .model = &std.Target.x86.cpu.skylake,
    .features = std.Target.x86.featureSet(&[_]std.Target.x86.Feature{
        .@"64bit",
        .adx,
        .aes,
        .allow_light_256_bit,
        .avx,
        .avx2,
        .bmi,
        .bmi2,
        .clflushopt,
        .cmov,
        .crc32,
        .cx16,
        .cx8,
        .ermsb,
        .f16c,
        .false_deps_popcnt,
        .fast_15bytenop,
        .fast_gather,
        .fast_scalar_fsqrt,
        .fast_shld_rotate,
        .fast_variable_crosslane_shuffle,
        .fast_variable_perlane_shuffle,
        .fast_vector_fsqrt,
        .fma,
        .fsgsbase,
        .fxsr,
        .idivq_to_divl,
        .invpcid,
        .lzcnt,
        .macrofusion,
        .mmx,
        .movbe,
        .no_bypass_delay_blend,
        .no_bypass_delay_mov,
        .no_bypass_delay_shuffle,
        .nopl,
        .pclmul,
        .popcnt,
        .prfchw,
        .rdrnd,
        .rdseed,
        .sahf,
        .sgx,
        .slow_3ops_lea,
        .sse,
        .sse2,
        .sse3,
        .sse4_1,
        .sse4_2,
        .ssse3,
        .vzeroupper,
        .x87,
        .xsave,
        .xsavec,
        .xsaveopt,
        .xsaves,
    }),
};
pub const os = std.Target.Os{
    .tag = .linux,
    .version_range = .{ .linux = .{
        .range = .{
            .min = .{
                .major = 6,
                .minor = 1,
                .patch = 53,
            },
            .max = .{
                .major = 6,
                .minor = 1,
                .patch = 53,
            },
        },
        .glibc = .{
            .major = 2,
            .minor = 36,
            .patch = 0,
        },
    }},
};

[jacobly0]

I see your backend assert and raise you a new Module assert.

diff --git a/src/Module.zig b/src/Module.zig
index eda4624bd0..d53393ba61 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -6382,6 +6382,12 @@ pub const UnionLayout = struct {
 };
 
 pub fn getUnionLayout(mod: *Module, u: InternPool.UnionType) UnionLayout {
+    const layout = mod.getUnionLayoutInner(u);
+    assert(layout.abi_align.check(layout.abi_size));
+    return layout;
+}
+
+fn getUnionLayoutInner(mod: *Module, u: InternPool.UnionType) UnionLayout {
     const ip = &mod.intern_pool;
     assert(u.haveLayout(ip));
     var most_aligned_field: u32 = undefined;

The first time I hit this assert is on this result, which I can't make heads or tails of (yes alignments are being displayed correctly as their tag name, not integer value):

(Module.UnionLayout) layout = {
  abi_size = 7
  abi_align = 8
  most_aligned_field = 1
  most_aligned_field_size = 56
  biggest_field = 1
  payload_size = 56
  payload_align = 8
  tag_align = 1
  tag_size = 1
  padding = 7
}