capy-language
Store some variables in registers instead of always using the stack
Problem
Currently, all local variables are stored in stack slots. This can create unnecessary stack stores and loads even when a variable's address is never obtained
Proposed Solution
codegen should check to see if a variable is ever aliased with ^. This could probably be done in either the hir or hir_ty crates during lowering or type checking. Maybe when an Expr::Ref is created/parsed it would check to see if it's inner expression was a Variable before marking that variable as "aliased".
codegen would then check this flag (and Ty::is_aggregate) to know if it should allocate stack space for the variable or if it should instead use cranelift_frontend::Variable
Notes
Future optimizations could probably be made if it's known that a variable is never aliased. Structs could be split up into separate cranelift_frontend::Variables for their different fields. Although this would also need to check if a variable was passed as an argument.
In the same stroke it would probably be good to perform stack_addr instructions only when absolutely necessary.
probably would lead to cranelift having to use less fuel on analyzing them.
This would probably be possible by having functions like compile_expr_with_args return an enum containing either a stack slot or a value.
