missing async spill when returning a function call of async fn with error union return value

[andrewrk]

const std = @import("std");
const expect = std.testing.expect;

var global_frame: anyframe = undefined;

test "try async call" {
    var f = async atest();
    resume global_frame;
    // TODO need https://github.com/ziglang/zig/issues/3157 for this next line
    //expect((noasync await f) == 1234);
}

fn atest() !i32 {
    return fallible1();
}

fn fallible1() anyerror!i32 {
    suspend {
        global_frame = @frame();
    }
    return 1234;
}

Expected to pass. Actual output:

Instruction does not dominate all uses!
  %20 = load { i32, i16 }*, { i32, i16 }** %3, align 8, !dbg !1039
  %31 = bitcast { i32, i16 }* %20 to i8*, !dbg !1039
LLVM ERROR: Broken module found, compilation aborted!

Related: #3157 (for the convenience of the test case)

[Vexu]

This still seems to be happening.

test "correctly spill when returning the error union result of another async fn" {
    const S = struct {
        const Self = @This();
        term: ?(SpawnError!Term),

        pub const SpawnError = error{OutOfMemory};

        pub const Term = union(enum) {
            Exited: u32,
            Signal: u32,
            Stopped: u32,
            Unknown: u32,
        };

        var global_frame: anyframe = undefined;

        fn doTheTest(self: *Self) void {
            atest(self);
            if ((self.term.? catch unreachable) != .Exited) unreachable;
        }

        fn atest(self: *Self) void {
            self.term = fallible1(self);
        }

        fn fallible1(self: *Self) SpawnError!Term {
            suspend {
                global_frame = @frame();
            }
            return Term{.Exited = 0};
        }
    };
    var s = S {.term = undefined};
    _ = async s.doTheTest();
    resume S.global_frame;
}

Results in

broken LLVM module found: Instruction does not dominate all uses!
  %26 = load { %Term, i16 }*, { %Term, i16 }** %5, align 8, !dbg !1858
  %37 = bitcast { %Term, i16 }* %26 to i8*, !dbg !1858

[andrewrk]

Fixed by #4404

[andrewrk]

Landed in 014f66e

[czipperz]

@andrewrk Should you remove this comment

zig/lib/std/child_process.zig

Line 273 in 49f3def

// TODO https://github.com/ziglang/zig/issues/3190

?

[czipperz]

Unrelated but this looks like dead code

zig/lib/std/child_process.zig

Line 113 in 49f3def

errdefer allocator.destroy(child);

[andrewrk]

@andrewrk Should you remove this comment

Yes and collapse those 2 lines back into 1.

Unrelated but this looks like dead code

I think dead code in errdefers are ok. They document resource cleanup that would need to happen if you added additional code after that line.