Remove deprecated LLVM-style inline assembly

[tmiasko]

The llvm_asm! was deprecated back in #87590 1.56.0, with intention to remove
it once asm! was stabilized, which already happened in #91728 1.59.0. Now it
is time to remove llvm_asm! to avoid continued maintenance cost.

Closes #70173.
Closes #92794.
Closes #87612.
Closes #82065.

cc @rust-lang/wg-inline-asm

r? @Amanieu

[rust-highfive]

Some changes occured to the CTFE / Miri engine

cc @rust-lang/miri

Some changes occured to rustc_codegen_cranelift

cc @bjorn3

Some changes occured to rustc_codegen_gcc

cc @antoyo

[Amanieu]

compiler/rustc_builtin_macros/src/asm.rs has a suggestion to use llvm_asm! if it detects the legacy syntax. I think this detection code should just be removed entirely since the renaming of the old asm! to llvm_asm! happened 2 years ago.

[tmiasko]

compiler/rustc_builtin_macros/src/asm.rs has a suggestion to use llvm_asm! if it detects the legacy syntax. I think this detection code should just be removed entirely since the renaming of the old asm! to llvm_asm! happened 2 years ago.

Thanks. Removed.

[Amanieu]

@bors r+ rollup=never

[bors]

📌 Commit b085eb0 has been approved by Amanieu

[bors]

⌛ Testing commit b085eb0 with merge a34c079...

[bors]

☀️ Test successful - checks-actions
Approved by: Amanieu
Pushing a34c079 to master...

[rust-timer]

Finished benchmarking commit (a34c079): comparison url.

Summary: This change led to very large relevant mixed results 🤷 in compiler performance.

• Very large improvement in instruction counts (up to -7.5% on full builds of keccak check)
• Moderate regression in instruction counts (up to 1.0% on incr-unchanged builds of ctfe-stress-4 check)

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression

[bjorn3]

Those are nice perf improvements!

[Amanieu]

I was honestly not expecting that. It seems that MIR borrowck somehow got a speedup, most likely due to the removal of MutateMode?

[tmiasko]

In keccak-Chec-Full perf difference seems incidental, code generated for a very hot loop in iterate_to_fixpoint improved quite a bit):

--------------------------------------------------------------------------------
Ir             
--------------------------------------------------------------------------------
-1,715,117,584  PROGRAM TOTALS

--------------------------------------------------------------------------------
Ir             file:function
--------------------------------------------------------------------------------
 -596,852,099  ???:<rustc_mir_dataflow::framework::engine::Engine<rustc_mir_dataflow::impls::MaybeInitializedPlaces>>::iterate_to_fixpoint
 -596,805,748  ???:<rustc_mir_dataflow::framework::engine::Engine<rustc_mir_dataflow::impls::MaybeUninitializedPlaces>>::iterate_to_fixpoint
 -523,105,586  ???:<rustc_mir_dataflow::framework::engine::Engine<rustc_mir_dataflow::impls::EverInitializedPlaces>>::iterate_to_fixpoint

This seems more or less what happened in a different PR (similar diff / codegen change) https://perf.rust-lang.org/compare.html?start=38c22af0153cf8f920c01ef04493e8878401fd18&end=8c4a951b919d548bba16b6f209ed05b1647eba2c.

cc @oli-obk I suspect that in #92928 & #93007 you might be chasing a regression that is no longer there.