src/librustc_target/abi/call/riscv.rs

   1 // Reference: RISC-V ELF psABI specification
   2 // https://github.com/riscv/riscv-elf-psabi-doc
   3
   4 use crate::abi::call::{ArgType, FnType};
   5
   6 fn classify_ret_ty<Ty>(arg: &mut ArgType<'_, Ty>, xlen: u64) {
   7     // "Scalars wider than 2✕XLEN are passed by reference and are replaced in
   8     // the argument list with the address."
   9     // "Aggregates larger than 2✕XLEN bits are passed by reference and are
  10     // replaced in the argument list with the address, as are C++ aggregates
  11     // with nontrivial copy constructors, destructors, or vtables."
  12     if arg.layout.size.bits() > 2 * xlen {
  13         arg.make_indirect();
  14     }
  15
  16     // "When passed in registers, scalars narrower than XLEN bits are widened
  17     // according to the sign of their type up to 32 bits, then sign-extended to
  18     // XLEN bits."
  19     arg.extend_integer_width_to(xlen); // this method only affects integer scalars
  20 }
  21
  22 fn classify_arg_ty<Ty>(arg: &mut ArgType<'_, Ty>, xlen: u64) {
  23     // "Scalars wider than 2✕XLEN are passed by reference and are replaced in
  24     // the argument list with the address."
  25     // "Aggregates larger than 2✕XLEN bits are passed by reference and are
  26     // replaced in the argument list with the address, as are C++ aggregates
  27     // with nontrivial copy constructors, destructors, or vtables."
  28     if arg.layout.size.bits() > 2 * xlen {
  29         arg.make_indirect();
  30     }
  31
  32     // "When passed in registers, scalars narrower than XLEN bits are widened
  33     // according to the sign of their type up to 32 bits, then sign-extended to
  34     // XLEN bits."
  35     arg.extend_integer_width_to(xlen); // this method only affects integer scalars
  36 }
  37
  38 pub fn compute_abi_info<Ty>(fty: &mut FnType<'_, Ty>, xlen: u64) {
  39     if !fty.ret.is_ignore() {
  40         classify_ret_ty(&mut fty.ret, xlen);
  41     }
  42
  43     for arg in &mut fty.args {
  44         if arg.is_ignore() {
  45             continue;
  46         }
  47         classify_arg_ty(arg, xlen);
  48     }
  49 }