Posts tagged "compilers"

I followed one u8 through the four stages of the Rust compiler: HIR, MIR, LLVM IR, and assembly. The type is a word, then a field, then a width, then nothing. The u8 and u32 versions of the same function compile to the same two instructions, and the one check a type does produce is the debug overflow guard.

Two identifiers, two different jobs. DefId names a definition across the whole compiler pipeline and across crates. HirId points to a node in the syntax tree of the current crate. Mixing them up is the first stumbling block when reading rustc source code.