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Add support for storing code model to LLVM module IR

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This patch avoids undefined behavior by linking different object files.
Also this would it could be propagated properly to LTO.

See https://reviews.llvm.org/D52322 and https://reviews.llvm.org/D52323.

This patch is based on https://github.com/rust-lang/rust/pull/74002
This commit is contained in:
Hiroki Noda 2021-03-12 08:35:13 +09:00
parent 4a8b6f708c
commit 8357e57346
5 changed files with 36 additions and 1 deletions
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8
compiler/rustc_codegen_llvm/src/context.rs
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@ -1,4 +1,5 @@
use crate::attributes;
use crate::back::write::to_llvm_code_model;
use crate::callee::get_fn;
use crate::coverageinfo;
use crate::debuginfo;
@ -181,6 +182,13 @@ pub unsafe fn create_module(
}
}
// Linking object files with different code models is undefined behavior
// because the compiler would have to generate additional code (to span
// longer jumps) if a larger code model is used with a smaller one.
//
// See https://reviews.llvm.org/D52322 and https://reviews.llvm.org/D52323.
llvm::LLVMRustSetModuleCodeModel(llmod, to_llvm_code_model(sess.code_model()));
// If skipping the PLT is enabled, we need to add some module metadata
// to ensure intrinsic calls don't use it.
if !sess.needs_plt() {