diff options
Diffstat (limited to 'compiler/GHC/CoreToStg')
| -rw-r--r-- | compiler/GHC/CoreToStg/Prep.hs | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/compiler/GHC/CoreToStg/Prep.hs b/compiler/GHC/CoreToStg/Prep.hs index 9ca8bff0c9..2be595e8d4 100644 --- a/compiler/GHC/CoreToStg/Prep.hs +++ b/compiler/GHC/CoreToStg/Prep.hs @@ -112,6 +112,17 @@ The goal of this pass is to prepare for code generation. and doing so would be tiresome because then we'd need to substitute in types and coercions. + We need to clone ids for two reasons: + + Things associated with labels in the final code must be truly unique in + order to avoid labels being shadowed in the final output. + + Even binders without info tables like function arguments or alternative + bound binders must be unique at least in their type/unique combination. + We only emit a single declaration for each binder when compiling to C + so if binders are not unique we would either get duplicate declarations + or misstyped variables. The later happend in #22402. + + We heavily use unique-keyed maps in the backend which can go wrong when + ids with the same unique are meant to represent the same variable. + 7. Give each dynamic CCall occurrence a fresh unique; this is rather like the cloning step above. |