Refactor call & function handling in trans, enable MIR bootstrap.

[eddyb]

Non-Rust and Rust ABIs were combined into a common codepath, which means:

• The ugly __rust_abi "clown shoes" shim for C->Rust FFI is gone, fixes #10116.
• Methods, including virtual ones support non-Rust ABIs, closes #30235.
• Non-Rust ABIs also pass fat pointers in two arguments; the result should be identical.
• Zero-sized types are never passed as arguments; again, behavior shouldn't change.

Additionally, MIR support for calling intrinsics (through old trans) was implemented.
Alongside assorted fixes, it enabled MIR to launch 🚀 and do a complete bootstrap.
To try it yourself, ./configure --enable-orbit or make RUSTFLAGS="-Z orbit".

[alexcrichton]

r? @nikomatsakis

(just making sure an assignment is given, feel free to delegate elsewhere)

[bors]

☔️ The latest upstream changes (presumably #31606) made this pull request unmergeable. Please resolve the merge conflicts.

[eddyb]

Status: I can build snap-stage3 with MIR forced on for everything.
These are the common run-pass failures for stage1 and stage2:
(that means they are likely MIR trans bugs and not due to miscompiled rustc)

failures:
    [run-pass] run-pass/allocator-override.rs
    [run-pass] run-pass/asm-in-out-operand.rs
    [run-pass] run-pass/asm-indirect-memory.rs
    [run-pass] run-pass/asm-out-assign.rs
    [run-pass] run-pass/associated-const-type-parameters.rs
    [run-pass] run-pass/backtrace-debuginfo.rs
    [run-pass] run-pass/const-str-ptr.rs
    [run-pass] run-pass/ignore-all-the-things.rs
    [run-pass] run-pass/int-abs-overflow.rs
    [run-pass] run-pass/issue-14936.rs
    [run-pass] run-pass/issue-15080.rs
    [run-pass] run-pass/issue-15104.rs
    [run-pass] run-pass/issue-23338-ensure-param-drop-order.rs
    [run-pass] run-pass/issue-7784.rs
    [run-pass] run-pass/issue-8460.rs
    [run-pass] run-pass/issue-8860.rs
    [run-pass] run-pass/match-vec-alternatives.rs
    [run-pass] run-pass/mir_raw_fat_ptr.rs
    [run-pass] run-pass/num-wrapping.rs
    [run-pass] run-pass/out-of-stack.rs
    [run-pass] run-pass/simd-intrinsic-generic-cast.rs
    [run-pass] run-pass/simd-intrinsic-generic-elements.rs
    [run-pass] run-pass/super-fast-paren-parsing.rs
    [run-pass] run-pass/vec-matching-fixed.rs
    [run-pass] run-pass/vec-matching-fold.rs
    [run-pass] run-pass/vec-matching-legal-tail-element-borrow.rs
    [run-pass] run-pass/vec-matching.rs
    [run-pass] run-pass/vec-tail-matching.rs
    [run-pass] run-pass/zero-size-type-destructors.rs

The only run-pass test that only fails in stage2 is run-pass/super-fast-paren-parsing.rs, which ends up in a stack overflow in rustc (@arielb1 was talking about needing llvm lifetime intrinsics to prevent this, I think).

@rust-lang/tools If I provide a flag to enable MIR trans for everything, and an attribute to mark functions which can't be yet properly translated via MIR, would it be possible to have buildbot ensure MIR doesn't regress?

[nikomatsakis]

‼️ 😲

[alexcrichton]

@eddyb I'd be fine at least adding a MIR bot! If it's a ./configure switch just lemme know and I can set up something like auto-linux-64-opt-mir or something like that.

Do you think MIR will want platform coverage as well? A Linux/OSX/Windows builder, or just one with it enabled?

[eddyb]

@alexcrichton Before the next snapshot, make RUSTFLAGS_STAGE1="-Z orbit" RUSTFLAGS_STAGE2=-"Z orbit", after that just make RUSTFLAGS="-Z orbit".

Sadly, it doesn't look like tests inherit RUSTFLAGS_STAGEn, just RUSTFLAGS, so we might need a snapshot anyway.

We'll want at least a non-MSVC and a MSVC builder, because of the differences in how unwinding works there.

[alexcrichton]

Ok, sounds like a linux + MSVC builder, and can you add this as a ./configure option? That'll be easiest to add to our build matrix.

[eddyb]

@alexcrichton Does that last commit look good?

[alexcrichton]

Looks good to me!

[eddyb]

Down to 9 run-pass MIR failures:

    [run-pass] run-pass/backtrace-debuginfo.rs
    [run-pass] run-pass/const-str-ptr.rs
    [run-pass] run-pass/int-abs-overflow.rs
    [run-pass] run-pass/issue-23338-ensure-param-drop-order.rs
    [run-pass] run-pass/issue-8460.rs
    [run-pass] run-pass/issue-8860.rs
    [run-pass] run-pass/mir_raw_fat_ptr.rs
    [run-pass] run-pass/simd-intrinsic-generic-elements.rs
    [run-pass] run-pass/zero-size-type-destructors.rs

I'll just start tagging them with #[rustc_no_mir], this PR is getting kind of long...

[eddyb]

@bors r=nikomatsakis force

[bors]

📌 Commit e177207 has been approved by nikomatsakis

[bors]

⌛️ Testing commit e177207 with merge 3c572b6...

[bors]

💔 Test failed - auto-win-gnu-64-opt

[eddyb]

@bors r=nikomatsakis force

[bors]

📌 Commit b12dcde has been approved by nikomatsakis

[bors]

⌛️ Testing commit b12dcde with merge 235d774...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild

[jonas-schievink]

---

It's doing strictly more work, AFAICT, because we emit more IR (not sure exactly why yet).

Pretty impressive that translation still ends up being faster!