src/librustc_trans/cabi_arm.rs

   1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use abi::{FnType, ArgType, LayoutExt, Reg, RegKind, Uniform};
  12 use context::CrateContext;
  13 use llvm::CallConv;
  14
  15 fn is_homogeneous_aggregate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, arg: &mut ArgType<'tcx>)
  16                                      -> Option<Uniform> {
  17     arg.layout.homogeneous_aggregate(ccx).and_then(|unit| {
  18         let size = arg.layout.size(ccx);
  19
  20         // Ensure we have at most four uniquely addressable members.
  21         if size > unit.size.checked_mul(4, ccx).unwrap() {
  22             return None;
  23         }
  24
  25         let valid_unit = match unit.kind {
  26             RegKind::Integer => false,
  27             RegKind::Float => true,
  28             RegKind::Vector => size.bits() == 64 || size.bits() == 128
  29         };
  30
  31         if valid_unit {
  32             Some(Uniform {
  33                 unit,
  34                 total: size
  35             })
  36         } else {
  37             None
  38         }
  39     })
  40 }
  41
  42 fn classify_ret_ty<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ret: &mut ArgType<'tcx>, vfp: bool) {
  43     if !ret.layout.is_aggregate() {
  44         ret.extend_integer_width_to(32);
  45         return;
  46     }
  47
  48     if vfp {
  49         if let Some(uniform) = is_homogeneous_aggregate(ccx, ret) {
  50             ret.cast_to(ccx, uniform);
  51             return;
  52         }
  53     }
  54
  55     let size = ret.layout.size(ccx);
  56     let bits = size.bits();
  57     if bits <= 32 {
  58         let unit = if bits <= 8 {
  59             Reg::i8()
  60         } else if bits <= 16 {
  61             Reg::i16()
  62         } else {
  63             Reg::i32()
  64         };
  65         ret.cast_to(ccx, Uniform {
  66             unit,
  67             total: size
  68         });
  69         return;
  70     }
  71     ret.make_indirect(ccx);
  72 }
  73
  74 fn classify_arg_ty<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, arg: &mut ArgType<'tcx>, vfp: bool) {
  75     if !arg.layout.is_aggregate() {
  76         arg.extend_integer_width_to(32);
  77         return;
  78     }
  79
  80     if vfp {
  81         if let Some(uniform) = is_homogeneous_aggregate(ccx, arg) {
  82             arg.cast_to(ccx, uniform);
  83             return;
  84         }
  85     }
  86
  87     let align = arg.layout.align(ccx).abi();
  88     let total = arg.layout.size(ccx);
  89     arg.cast_to(ccx, Uniform {
  90         unit: if align <= 4 { Reg::i32() } else { Reg::i64() },
  91         total
  92     });
  93 }
  94
  95 pub fn compute_abi_info<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, fty: &mut FnType<'tcx>) {
  96     // If this is a target with a hard-float ABI, and the function is not explicitly
  97     // `extern "aapcs"`, then we must use the VFP registers for homogeneous aggregates.
  98     let vfp = ccx.sess().target.target.llvm_target.ends_with("hf")
  99         && fty.cconv != CallConv::ArmAapcsCallConv
 100         && !fty.variadic;
 101
 102     if !fty.ret.is_ignore() {
 103         classify_ret_ty(ccx, &mut fty.ret, vfp);
 104     }
 105
 106     for arg in &mut fty.args {
 107         if arg.is_ignore() { continue; }
 108         classify_arg_ty(ccx, arg, vfp);
 109     }
 110 }