bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #87916 - nbdd0121:black_box, r=nagisa

Browse source 
Implement `black_box` using intrinsic

Introduce `black_box` intrinsic, as suggested in https://github.com/rust-lang/rust/pull/87590#discussion_r680468700.

This is still codegenned as empty inline assembly for LLVM. For MIR interpretation and cranelift it's treated as identity.

cc `@Amanieu` as this is related to inline assembly
cc `@bjorn3` for rustc_codegen_cranelift changes
cc `@RalfJung` as this affects MIRI

r? `@nagisa` I suppose
This commit is contained in:
bors 2021-08-12 21:04:07 +00:00
commit 0fa3190394
9 changed files with 52 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

2
compiler/rustc_mir/src/interpret/intrinsics.rs
View file

@ -465,7 +465,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
);
self.copy_op(&self.operand_index(&args[0], index)?, dest)?;
}
sym::likely | sym::unlikely => {
sym::likely | sym::unlikely | sym::black_box => {
// These just return their argument
self.copy_op(&args[0], dest)?;
}