Compiling rustc with -Zrandomize-layout triggers assert in rustc_codegen_llvm/src/type_of.rs

[the8472]

#101339 aims to enable -Zrandomize-layout in CI. Attempting to merge it results in this build failure.

It reproduces locally by checking out merge commit 7613125631f18e024b670e1764b3eeeca257045e and running ./src/ci/docker/run.sh x86_64-gnu-llvm-13.

With RUSTC_LOG=rustc_codegen_llvm::type_of=debug I get

DEBUG rustc_codegen_llvm::type_of struct_llfields: TyAndLayout {
    ty: debuginfo::metadata::type_map::UniqueTypeId,
    layout: Layout {
        size: Size(32 bytes),
        align: AbiAndPrefAlign {
            abi: Align(8 bytes),
            pref: Align(8 bytes),
        },
        abi: Aggregate {
            sized: true,
        },
        fields: Arbitrary {
            offsets: [
                Size(24 bytes),
                Size(16 bytes),
                Size(4 bytes),
            ],
            memory_index: [
                2,
                0,
                1,
            ],
        },
        largest_niche: None,
        variants: Single {
            index: 3,
        },
    },
}
DEBUG rustc_codegen_llvm::type_of struct_llfields: 1: TyAndLayout { ty: rustc_target::abi::VariantIdx, layout: Layout { size: Size(4 bytes), align: AbiAndPrefAlign { abi: Align(4 bytes), pref: Align(8 bytes) }, abi: Scalar(Initialized { value: Int(I32, false), valid_range: 0..=4294967040 }), fields: Arbitrary { offsets: [Size(0 bytes)], memory_index: [0] }, largest_niche: Some(Niche { offset: Size(0 bytes), value: Int(I32, false), valid_range: 0..=4294967040 }), variants: Single { index: 0 } } } offset: Size(0 bytes) target_offset: Size(16 bytes) effective_field_align: 4
DEBUG rustc_codegen_llvm::type_of     padding before: Size(16 bytes)
DEBUG rustc_codegen_llvm::type_of struct_llfields: 2: TyAndLayout { ty: debuginfo::metadata::type_map::private::HiddenZst, layout: Layout { size: Size(0 bytes), align: AbiAndPrefAlign { abi: Align(1 bytes), pref: Align(8 bytes) }, abi: Aggregate { sized: true }, fields: Arbitrary { offsets: [], memory_index: [] }, largest_niche: None, variants: Single { index: 0 } } } offset: Size(20 bytes) target_offset: Size(4 bytes) effective_field_align: 1
thread 'rustc' panicked at 'assertion failed: target_offset >= offset', compiler/rustc_codegen_llvm/src/type_of.rs:129:9
stack backtrace:
   0:     0x7f282b105efd - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::heec03eb9b2106f99
   1:     0x7f282b16bf79 - core::fmt::write::hdc2190284bc6d0d4
   2:     0x7f282b0f6e41 - std::io::Write::write_fmt::h42741f15affd0ecb
   3:     0x7f282b108f0e - std::panicking::default_hook::{{closure}}::ha3e47422d6cfd2aa
   4:     0x7f282b108bd7 - std::panicking::default_hook::h06e3da70e0c4e264
   5:     0x7f282bafaa74 - rustc_driver[3636f0421e6d8c75]::DEFAULT_HOOK::{closure#0}::{closure#0}
   6:     0x7f282b1096b7 - std::panicking::rust_panic_with_hook::h332b5ce1ed540d19
   7:     0x7f282b1094aa - std::panicking::begin_panic_handler::{{closure}}::hf2b83e53a3e49fbf
   8:     0x7f282b106464 - std::sys_common::backtrace::__rust_end_short_backtrace::hc87a83fccecce6d2
   9:     0x7f282b1091a2 - rust_begin_unwind
  10:     0x7f282b0bcc23 - core::panicking::panic_fmt::h55dfedac6f6597d4
  11:     0x7f282b0bcaf3 - core::panicking::panic::h858d0a26258d295c
  12:     0x7f282bd37d83 - rustc_codegen_llvm[7b6a0d1032d5a3f0]::type_of::struct_llfields
  13:     0x7f282bd20b65 - <rustc_target[8d82747607a543bd]::abi::TyAndLayout<rustc_middle[10b8fe355026857d]::ty::Ty> as rustc_codegen_llvm[7b6a0d1032d5a3f0]::type_of::LayoutLlvmExt>::llvm_type
  14:     0x7f282bd258ba - <rustc_codegen_ssa[ace718b546837800]::mir::place::PlaceRef<&rustc_codegen_llvm[7b6a0d1032d5a3f0]::llvm_::ffi::Value>>::project_downcast::<rustc_codegen_llvm[7b6a0d1032d5a3f0]::builder::Builder>
  15:     0x7f282be56507 - <rustc_codegen_ssa[ace718b546837800]::mir::FunctionCx<rustc_codegen_llvm[7b6a0d1032d5a3f0]::builder::Builder>>::codegen_place
  16:     0x7f282be47b7d - <rustc_codegen_ssa[ace718b546837800]::mir::FunctionCx<rustc_codegen_llvm[7b6a0d1032d5a3f0]::builder::Builder>>::codegen_rvalue_operand
  17:     0x7f282be4e74a - <rustc_codegen_ssa[ace718b546837800]::mir::FunctionCx<rustc_codegen_llvm[7b6a0d1032d5a3f0]::builder::Builder>>::codegen_block
  18:     0x7f282be43446 - rustc_codegen_ssa[ace718b546837800]::mir::codegen_mir::<rustc_codegen_llvm[7b6a0d1032d5a3f0]::builder::Builder>
  19:     0x7f282bd57937 - rustc_codegen_ssa[ace718b546837800]::base::codegen_instance::<rustc_codegen_llvm[7b6a0d1032d5a3f0]::builder::Builder>

CC @Kixiron

[Kixiron]

I'm fairly sure I fixed this in #97861 but I haven't worked on that PR in a while

[WaffleLapkin]

is this still happening?

[the8472]

No longer seems to happen.