src/librustc_codegen_llvm/va_arg.rs

   1 use builder::Builder;
   2 use rustc_codegen_ssa::mir::operand::OperandRef;
   3 use rustc_codegen_ssa::traits::{BaseTypeMethods, BuilderMethods, ConstMethods, DerivedTypeMethods};
   4 use rustc::ty::layout::{Align, HasDataLayout, HasTyCtxt, LayoutOf, Size};
   5 use rustc::ty::Ty;
   6 use type_::Type;
   7 use type_of::LayoutLlvmExt;
   8 use value::Value;
   9
  10 #[allow(dead_code)]
  11 fn round_pointer_up_to_alignment(
  12     bx: &mut Builder<'a, 'll, 'tcx>,
  13     addr: &'ll Value,
  14     align: Align,
  15     ptr_ty: &'ll Type
  16 ) -> &'ll Value {
  17     let mut ptr_as_int = bx.ptrtoint(addr, bx.cx().type_isize());
  18     ptr_as_int = bx.add(ptr_as_int, bx.cx().const_i32(align.bytes() as i32 - 1));
  19     ptr_as_int = bx.and(ptr_as_int, bx.cx().const_i32(-(align.bytes() as i32)));
  20     bx.inttoptr(ptr_as_int, ptr_ty)
  21 }
  22
  23 fn emit_direct_ptr_va_arg(
  24     bx: &mut Builder<'a, 'll, 'tcx>,
  25     list: OperandRef<'tcx, &'ll Value>,
  26     llty: &'ll Type,
  27     size: Size,
  28     align: Align,
  29     slot_size: Align,
  30     allow_higher_align: bool
  31 ) -> (&'ll Value, Align) {
  32     let va_list_ptr_ty = bx.cx().type_ptr_to(bx.cx.type_i8p());
  33     let va_list_addr = if list.layout.llvm_type(bx.cx) != va_list_ptr_ty {
  34         bx.bitcast(list.immediate(), va_list_ptr_ty)
  35     } else {
  36         list.immediate()
  37     };
  38
  39     let ptr = bx.load(va_list_addr, bx.tcx().data_layout.pointer_align.abi);
  40
  41     let (addr, addr_align) = if allow_higher_align && align > slot_size {
  42         (round_pointer_up_to_alignment(bx, ptr, align, bx.cx().type_i8p()), align)
  43     } else {
  44         (ptr, slot_size)
  45     };
  46
  47
  48     let aligned_size = size.align_to(slot_size).bytes() as i32;
  49     let full_direct_size = bx.cx().const_i32(aligned_size);
  50     let next = bx.inbounds_gep(addr, &[full_direct_size]);
  51     bx.store(next, va_list_addr, bx.tcx().data_layout.pointer_align.abi);
  52
  53     if size.bytes() < slot_size.bytes() &&
  54             &*bx.tcx().sess.target.target.target_endian == "big" {
  55         let adjusted_size = bx.cx().const_i32((slot_size.bytes() - size.bytes()) as i32);
  56         let adjusted = bx.inbounds_gep(addr, &[adjusted_size]);
  57         (bx.bitcast(adjusted, bx.cx().type_ptr_to(llty)), addr_align)
  58     } else {
  59         (bx.bitcast(addr, bx.cx().type_ptr_to(llty)), addr_align)
  60     }
  61 }
  62
  63 fn emit_ptr_va_arg(
  64     bx: &mut Builder<'a, 'll, 'tcx>,
  65     list: OperandRef<'tcx, &'ll Value>,
  66     target_ty: Ty<'tcx>,
  67     indirect: bool,
  68     slot_size: Align,
  69     allow_higher_align: bool
  70 ) -> &'ll Value {
  71     let layout = bx.cx.layout_of(target_ty);
  72     let (llty, size, align) = if indirect {
  73         (bx.cx.layout_of(bx.cx.tcx.mk_imm_ptr(target_ty)).llvm_type(bx.cx),
  74          bx.cx.data_layout().pointer_size,
  75          bx.cx.data_layout().pointer_align)
  76     } else {
  77         (layout.llvm_type(bx.cx),
  78          layout.size,
  79          layout.align)
  80     };
  81     let (addr, addr_align) = emit_direct_ptr_va_arg(bx, list, llty, size, align.abi,
  82                                                     slot_size, allow_higher_align);
  83     if indirect {
  84         let tmp_ret = bx.load(addr, addr_align);
  85         bx.load(tmp_ret, align.abi)
  86     } else {
  87         bx.load(addr, addr_align)
  88     }
  89 }
  90
  91 pub(super) fn emit_va_arg(
  92     bx: &mut Builder<'a, 'll, 'tcx>,
  93     addr: OperandRef<'tcx, &'ll Value>,
  94     target_ty: Ty<'tcx>,
  95 ) -> &'ll Value {
  96     // Determine the va_arg implementation to use. The LLVM va_arg instruction
  97     // is lacking in some instances, so we should only use it as a fallback.
  98     let target = &bx.cx.tcx.sess.target.target;
  99     let arch = &bx.cx.tcx.sess.target.target.arch;
 100     match (&**arch, target.options.is_like_windows) {
 101         // Windows x86
 102         ("x86", true) => {
 103             emit_ptr_va_arg(bx, addr, target_ty, false,
 104                             Align::from_bytes(4).unwrap(), false)
 105         }
 106         // Generic x86
 107         ("x86", _) => {
 108             emit_ptr_va_arg(bx, addr, target_ty, false,
 109                             Align::from_bytes(4).unwrap(), true)
 110         }
 111         // Windows Aarch64
 112         ("aarch4", true) => {
 113             emit_ptr_va_arg(bx, addr, target_ty, false,
 114                             Align::from_bytes(8).unwrap(), false)
 115         }
 116         // iOS Aarch64
 117         ("aarch4", _) if target.target_os == "ios" => {
 118             emit_ptr_va_arg(bx, addr, target_ty, false,
 119                             Align::from_bytes(8).unwrap(), true)
 120         }
 121         // Windows x86_64
 122         ("x86_64", true) => {
 123             let target_ty_size = bx.cx.size_of(target_ty).bytes();
 124             let indirect = if target_ty_size > 8 || !target_ty_size.is_power_of_two() {
 125                 true
 126             } else {
 127                 false
 128             };
 129             emit_ptr_va_arg(bx, addr, target_ty, indirect,
 130                             Align::from_bytes(8).unwrap(), false)
 131         }
 132         // For all other architecture/OS combinations fall back to using
 133         // the LLVM va_arg instruction.
 134         // https://llvm.org/docs/LangRef.html#va-arg-instruction
 135         _ => {
 136             let va_list = if (target.arch == "aarch64" ||
 137                               target.arch == "x86_64" ||
 138                               target.arch == "powerpc") &&
 139                              !target.options.is_like_windows {
 140                 bx.load(addr.immediate(), bx.tcx().data_layout.pointer_align.abi)
 141             } else {
 142                 addr.immediate()
 143             };
 144             bx.va_arg(va_list, bx.cx.layout_of(target_ty).llvm_type(bx.cx))
 145         }
 146     }
 147 }
 148