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LLVM 18 x86 data layout update

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With https://reviews.llvm.org/D86310 LLVM now has i128 aligned to
16-bytes on x86 based platforms. This will be in LLVM-18. This patch
updates all our spec targets to be 16-byte aligned, and removes the
alignment when speaking to older LLVM.

This results in Rust overaligning things relative to LLVM on older LLVMs.

This alignment change was discussed in rust-lang/compiler-team#683

See #54341 for additional information about why this is happening and
where this will be useful in the future.

This *does not* stabilize `i128`/`u128` for FFI.
This commit is contained in:
Matthew Maurer 2023-10-12 17:36:01 +00:00 • committed by Nikita Popov
parent 16fadb3f25
commit dbff90c2a7
51 changed files with 103 additions and 85 deletions
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8
compiler/rustc_codegen_llvm/src/context.rs
View file

@ -145,6 +145,14 @@ pub unsafe fn create_module<'ll>(
.replace("-Fi64", "");
}
}
if llvm_version < (18, 0, 0) {
if sess.target.arch == "x86" || sess.target.arch == "x86_64" {
// LLVM 18 adjusts i128 to be 128-bit aligned on x86 variants.
// Earlier LLVMs leave this as default alignment, so remove it.
// See https://reviews.llvm.org/D86310
target_data_layout = target_data_layout.replace("-i128:128", "");
}
}
// Ensure the data-layout values hardcoded remain the defaults.
if sess.target.is_builtin {