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Comment by ChrisSD | Hacker News Reader

Is there anything of particular interest to Rust? I'm know Rust is built on LLVM (for both good and ill but mostly good).

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Rust updates LLVM more commonly than LLVM does stable releases, so it has been using a version somewhere between LLVM 6 and LLVM 7 for a while already.

I think one of the main areas that improved in LLVM 7 relative to LLVM 6 that Rust cares about is better support for WASM in LLD.

We also had to turn off noalias for &mut T for a while, due to bugs, and that was fixed fairly recently, and we turned it back on. I think that was post LLVM 6, but I can't quite remember.

Looks like it was as of LLVM 6: https://github.com/rust-lang/rust/pull/50744

Rust 1.30 (now in beta) has already moved to a newer snapshot of trunk, LLVM 8ish.

According to the "Update to LLVM 7" ticket for Rust (https://github.com/rust-lang/rust/issues/50543), many of the points of interest are in LLD, especially in WASM support:

    LLD has implemented --gc-sections for wasm
    LLD has implemented DWARF debugging information sections for wasm
    LLD has natively implemented concatenation of custom sections for wasm
    LLD has gained the ability to place the stack first in a wasm module's memory layout, reducing the corruption that happens on a stack overflow
    LLD option to not merge data segments
    Some SIMD generic float intrinsics have been fixed
    LLD optimizing further the size of release binaries
    LLD supports @-file syntax

Other things which mention LLVM 7 in the Rust bug tracker:

https://github.com/rust-lang/rust/issues/52457 "use funnel shift intrinsic to implement rotates"

https://github.com/rust-lang/rust/issues/52323 "emscripten already supports the wasm backend in LLVM7, so we should move the current emscripten-llvm from version 4.0 to that, so that we can remove all the workarounds lying around for LLVM < 5.0 (LLVM 5 is the new minimum supported version)."

https://github.com/rust-lang/rust/issues/49740 "Use separate memcpy source/dest alignments in LLVM 7"

https://github.com/rust-lang/rust/issues/51872 "Simplify u128->f32 casts thanks to LLVM r334777"

edit to add: rustc stable 1.29.0 already uses LLVM 7, and nightly is already using LLVM 8; rustc frequently switches to the new LLVM release when it is branched, it doesn't wait until it is released:

  $ rustc +stable --version --verbose
  rustc 1.29.0 (aa3ca1994 2018-09-11)
  binary: rustc
  commit-hash: aa3ca1994904f2e056679fce1f185db8c7ed2703
  commit-date: 2018-09-11
  host: x86_64-apple-darwin
  release: 1.29.0
  LLVM version: 7.0
  $ rustc +nightly --version --verbose
  rustc 1.30.0-nightly (79fcc58b2 2018-09-18)
  binary: rustc
  commit-hash: 79fcc58b24d85743d025fd880fca55748662ed3e
  commit-date: 2018-09-18
  host: x86_64-apple-darwin
  release: 1.30.0-nightly
  LLVM version: 8.0

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