src/librustc_codegen_llvm/common.rs

   1 #![allow(non_camel_case_types, non_snake_case)]
   2
   3 //! Code that is useful in various codegen modules.
   4
   5 use crate::llvm::{self, True, False, Bool, BasicBlock, OperandBundleDef};
   6 use crate::abi;
   7 use crate::consts;
   8 use crate::type_::Type;
   9 use crate::type_of::LayoutLlvmExt;
  10 use crate::value::Value;
  11 use rustc_codegen_ssa::traits::*;
  12
  13 use crate::consts::const_alloc_to_llvm;
  14 use rustc::ty::layout::{HasDataLayout, LayoutOf, self, TyLayout, Size};
  15 use rustc::mir::interpret::{Scalar, AllocKind, Allocation};
  16 use rustc_codegen_ssa::mir::place::PlaceRef;
  17
  18 use libc::{c_uint, c_char};
  19
  20 use syntax::symbol::LocalInternedString;
  21 use syntax::ast::Mutability;
  22
  23 pub use crate::context::CodegenCx;
  24
  25 /*
  26 * A note on nomenclature of linking: "extern", "foreign", and "upcall".
  27 *
  28 * An "extern" is an LLVM symbol we wind up emitting an undefined external
  29 * reference to. This means "we don't have the thing in this compilation unit,
  30 * please make sure you link it in at runtime". This could be a reference to
  31 * C code found in a C library, or rust code found in a rust crate.
  32 *
  33 * Most "externs" are implicitly declared (automatically) as a result of a
  34 * user declaring an extern _module_ dependency; this causes the rust driver
  35 * to locate an extern crate, scan its compilation metadata, and emit extern
  36 * declarations for any symbols used by the declaring crate.
  37 *
  38 * A "foreign" is an extern that references C (or other non-rust ABI) code.
  39 * There is no metadata to scan for extern references so in these cases either
  40 * a header-digester like bindgen, or manual function prototypes, have to
  41 * serve as declarators. So these are usually given explicitly as prototype
  42 * declarations, in rust code, with ABI attributes on them noting which ABI to
  43 * link via.
  44 *
  45 * An "upcall" is a foreign call generated by the compiler (not corresponding
  46 * to any user-written call in the code) into the runtime library, to perform
  47 * some helper task such as bringing a task to life, allocating memory, etc.
  48 *
  49 */
  50
  51 /// A structure representing an active landing pad for the duration of a basic
  52 /// block.
  53 ///
  54 /// Each `Block` may contain an instance of this, indicating whether the block
  55 /// is part of a landing pad or not. This is used to make decision about whether
  56 /// to emit `invoke` instructions (e.g., in a landing pad we don't continue to
  57 /// use `invoke`) and also about various function call metadata.
  58 ///
  59 /// For GNU exceptions (`landingpad` + `resume` instructions) this structure is
  60 /// just a bunch of `None` instances (not too interesting), but for MSVC
  61 /// exceptions (`cleanuppad` + `cleanupret` instructions) this contains data.
  62 /// When inside of a landing pad, each function call in LLVM IR needs to be
  63 /// annotated with which landing pad it's a part of. This is accomplished via
  64 /// the `OperandBundleDef` value created for MSVC landing pads.
  65 pub struct Funclet<'ll> {
  66     cleanuppad: &'ll Value,
  67     operand: OperandBundleDef<'ll>,
  68 }
  69
  70 impl Funclet<'ll> {
  71     pub fn new(cleanuppad: &'ll Value) -> Self {
  72         Funclet {
  73             cleanuppad,
  74             operand: OperandBundleDef::new("funclet", &[cleanuppad]),
  75         }
  76     }
  77
  78     pub fn cleanuppad(&self) -> &'ll Value {
  79         self.cleanuppad
  80     }
  81
  82     pub fn bundle(&self) -> &OperandBundleDef<'ll> {
  83         &self.operand
  84     }
  85 }
  86
  87 impl BackendTypes for CodegenCx<'ll, 'tcx> {
  88     type Value = &'ll Value;
  89     type BasicBlock = &'ll BasicBlock;
  90     type Type = &'ll Type;
  91     type Funclet = Funclet<'ll>;
  92
  93     type DIScope = &'ll llvm::debuginfo::DIScope;
  94 }
  95
  96 impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
  97     fn const_null(&self, t: &'ll Type) -> &'ll Value {
  98         unsafe {
  99             llvm::LLVMConstNull(t)
 100         }
 101     }
 102
 103     fn const_undef(&self, t: &'ll Type) -> &'ll Value {
 104         unsafe {
 105             llvm::LLVMGetUndef(t)
 106         }
 107     }
 108
 109     fn const_int(&self, t: &'ll Type, i: i64) -> &'ll Value {
 110         unsafe {
 111             llvm::LLVMConstInt(t, i as u64, True)
 112         }
 113     }
 114
 115     fn const_uint(&self, t: &'ll Type, i: u64) -> &'ll Value {
 116         unsafe {
 117             llvm::LLVMConstInt(t, i, False)
 118         }
 119     }
 120
 121     fn const_uint_big(&self, t: &'ll Type, u: u128) -> &'ll Value {
 122         unsafe {
 123             let words = [u as u64, (u >> 64) as u64];
 124             llvm::LLVMConstIntOfArbitraryPrecision(t, 2, words.as_ptr())
 125         }
 126     }
 127
 128     fn const_bool(&self, val: bool) -> &'ll Value {
 129         self.const_uint(self.type_i1(), val as u64)
 130     }
 131
 132     fn const_i32(&self, i: i32) -> &'ll Value {
 133         self.const_int(self.type_i32(), i as i64)
 134     }
 135
 136     fn const_u32(&self, i: u32) -> &'ll Value {
 137         self.const_uint(self.type_i32(), i as u64)
 138     }
 139
 140     fn const_u64(&self, i: u64) -> &'ll Value {
 141         self.const_uint(self.type_i64(), i)
 142     }
 143
 144     fn const_usize(&self, i: u64) -> &'ll Value {
 145         let bit_size = self.data_layout().pointer_size.bits();
 146         if bit_size < 64 {
 147             // make sure it doesn't overflow
 148             assert!(i < (1<<bit_size));
 149         }
 150
 151         self.const_uint(self.isize_ty, i)
 152     }
 153
 154     fn const_u8(&self, i: u8) -> &'ll Value {
 155         self.const_uint(self.type_i8(), i as u64)
 156     }
 157
 158     fn const_cstr(
 159         &self,
 160         s: LocalInternedString,
 161         null_terminated: bool,
 162     ) -> &'ll Value {
 163         unsafe {
 164             if let Some(&llval) = self.const_cstr_cache.borrow().get(&s) {
 165                 return llval;
 166             }
 167
 168             let sc = llvm::LLVMConstStringInContext(self.llcx,
 169                                                     s.as_ptr() as *const c_char,
 170                                                     s.len() as c_uint,
 171                                                     !null_terminated as Bool);
 172             let sym = self.generate_local_symbol_name("str");
 173             let g = self.define_global(&sym[..], self.val_ty(sc)).unwrap_or_else(||{
 174                 bug!("symbol `{}` is already defined", sym);
 175             });
 176             llvm::LLVMSetInitializer(g, sc);
 177             llvm::LLVMSetGlobalConstant(g, True);
 178             llvm::LLVMRustSetLinkage(g, llvm::Linkage::InternalLinkage);
 179
 180             self.const_cstr_cache.borrow_mut().insert(s, g);
 181             g
 182         }
 183     }
 184
 185     fn const_str_slice(&self, s: LocalInternedString) -> &'ll Value {
 186         let len = s.len();
 187         let cs = consts::ptrcast(self.const_cstr(s, false),
 188             self.type_ptr_to(self.layout_of(self.tcx.mk_str()).llvm_type(self)));
 189         self.const_fat_ptr(cs, self.const_usize(len as u64))
 190     }
 191
 192     fn const_fat_ptr(
 193         &self,
 194         ptr: &'ll Value,
 195         meta: &'ll Value
 196     ) -> &'ll Value {
 197         assert_eq!(abi::FAT_PTR_ADDR, 0);
 198         assert_eq!(abi::FAT_PTR_EXTRA, 1);
 199         self.const_struct(&[ptr, meta], false)
 200     }
 201
 202     fn const_struct(
 203         &self,
 204         elts: &[&'ll Value],
 205         packed: bool
 206     ) -> &'ll Value {
 207         struct_in_context(self.llcx, elts, packed)
 208     }
 209
 210     fn const_array(&self, ty: &'ll Type, elts: &[&'ll Value]) -> &'ll Value {
 211         unsafe {
 212             return llvm::LLVMConstArray(ty, elts.as_ptr(), elts.len() as c_uint);
 213         }
 214     }
 215
 216     fn const_vector(&self, elts: &[&'ll Value]) -> &'ll Value {
 217         unsafe {
 218             return llvm::LLVMConstVector(elts.as_ptr(), elts.len() as c_uint);
 219         }
 220     }
 221
 222     fn const_bytes(&self, bytes: &[u8]) -> &'ll Value {
 223         bytes_in_context(self.llcx, bytes)
 224     }
 225
 226     fn const_get_elt(&self, v: &'ll Value, idx: u64) -> &'ll Value {
 227         unsafe {
 228             assert_eq!(idx as c_uint as u64, idx);
 229             let us = &[idx as c_uint];
 230             let r = llvm::LLVMConstExtractValue(v, us.as_ptr(), us.len() as c_uint);
 231
 232             debug!("const_get_elt(v={:?}, idx={}, r={:?})",
 233                    v, idx, r);
 234
 235             r
 236         }
 237     }
 238
 239     fn const_get_real(&self, v: &'ll Value) -> Option<(f64, bool)> {
 240         unsafe {
 241             if self.is_const_real(v) {
 242                 let mut loses_info: llvm::Bool = ::std::mem::uninitialized();
 243                 let r = llvm::LLVMConstRealGetDouble(v, &mut loses_info);
 244                 let loses_info = if loses_info == 1 { true } else { false };
 245                 Some((r, loses_info))
 246             } else {
 247                 None
 248             }
 249         }
 250     }
 251
 252     fn const_to_uint(&self, v: &'ll Value) -> u64 {
 253         unsafe {
 254             llvm::LLVMConstIntGetZExtValue(v)
 255         }
 256     }
 257
 258     fn is_const_integral(&self, v: &'ll Value) -> bool {
 259         unsafe {
 260             llvm::LLVMIsAConstantInt(v).is_some()
 261         }
 262     }
 263
 264     fn is_const_real(&self, v: &'ll Value) -> bool {
 265         unsafe {
 266             llvm::LLVMIsAConstantFP(v).is_some()
 267         }
 268     }
 269
 270     fn const_to_opt_u128(&self, v: &'ll Value, sign_ext: bool) -> Option<u128> {
 271         unsafe {
 272             if self.is_const_integral(v) {
 273                 let (mut lo, mut hi) = (0u64, 0u64);
 274                 let success = llvm::LLVMRustConstInt128Get(v, sign_ext,
 275                                                            &mut hi, &mut lo);
 276                 if success {
 277                     Some(hi_lo_to_u128(lo, hi))
 278                 } else {
 279                     None
 280                 }
 281             } else {
 282                 None
 283             }
 284         }
 285     }
 286
 287     fn scalar_to_backend(
 288         &self,
 289         cv: Scalar,
 290         layout: &layout::Scalar,
 291         llty: &'ll Type,
 292     ) -> &'ll Value {
 293         let bitsize = if layout.is_bool() { 1 } else { layout.value.size(self).bits() };
 294         match cv {
 295             Scalar::Bits { size: 0, .. } => {
 296                 assert_eq!(0, layout.value.size(self).bytes());
 297                 self.const_undef(self.type_ix(0))
 298             },
 299             Scalar::Bits { bits, size } => {
 300                 assert_eq!(size as u64, layout.value.size(self).bytes());
 301                 let llval = self.const_uint_big(self.type_ix(bitsize), bits);
 302                 if layout.value == layout::Pointer {
 303                     unsafe { llvm::LLVMConstIntToPtr(llval, llty) }
 304                 } else {
 305                     self.const_bitcast(llval, llty)
 306                 }
 307             },
 308             Scalar::Ptr(ptr) => {
 309                 let alloc_kind = self.tcx.alloc_map.lock().get(ptr.alloc_id);
 310                 let base_addr = match alloc_kind {
 311                     Some(AllocKind::Memory(alloc)) => {
 312                         let init = const_alloc_to_llvm(self, alloc);
 313                         if alloc.mutability == Mutability::Mutable {
 314                             self.static_addr_of_mut(init, alloc.align, None)
 315                         } else {
 316                             self.static_addr_of(init, alloc.align, None)
 317                         }
 318                     }
 319                     Some(AllocKind::Function(fn_instance)) => {
 320                         self.get_fn(fn_instance)
 321                     }
 322                     Some(AllocKind::Static(def_id)) => {
 323                         assert!(self.tcx.is_static(def_id).is_some());
 324                         self.get_static(def_id)
 325                     }
 326                     None => bug!("missing allocation {:?}", ptr.alloc_id),
 327                 };
 328                 let llval = unsafe { llvm::LLVMConstInBoundsGEP(
 329                     self.const_bitcast(base_addr, self.type_i8p()),
 330                     &self.const_usize(ptr.offset.bytes()),
 331                     1,
 332                 ) };
 333                 if layout.value != layout::Pointer {
 334                     unsafe { llvm::LLVMConstPtrToInt(llval, llty) }
 335                 } else {
 336                     self.const_bitcast(llval, llty)
 337                 }
 338             }
 339         }
 340     }
 341
 342     fn from_const_alloc(
 343         &self,
 344         layout: TyLayout<'tcx>,
 345         alloc: &Allocation,
 346         offset: Size,
 347     ) -> PlaceRef<'tcx, &'ll Value> {
 348         let init = const_alloc_to_llvm(self, alloc);
 349         let base_addr = self.static_addr_of(init, layout.align.abi, None);
 350
 351         let llval = unsafe { llvm::LLVMConstInBoundsGEP(
 352             self.const_bitcast(base_addr, self.type_i8p()),
 353             &self.const_usize(offset.bytes()),
 354             1,
 355         )};
 356         let llval = self.const_bitcast(llval, self.type_ptr_to(layout.llvm_type(self)));
 357         PlaceRef::new_sized(llval, layout, alloc.align)
 358     }
 359
 360     fn const_ptrcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value {
 361         consts::ptrcast(val, ty)
 362     }
 363 }
 364
 365 pub fn val_ty(v: &'ll Value) -> &'ll Type {
 366     unsafe {
 367         llvm::LLVMTypeOf(v)
 368     }
 369 }
 370
 371 pub fn bytes_in_context(llcx: &'ll llvm::Context, bytes: &[u8]) -> &'ll Value {
 372     unsafe {
 373         let ptr = bytes.as_ptr() as *const c_char;
 374         return llvm::LLVMConstStringInContext(llcx, ptr, bytes.len() as c_uint, True);
 375     }
 376 }
 377
 378 pub fn struct_in_context(
 379     llcx: &'a llvm::Context,
 380     elts: &[&'a Value],
 381     packed: bool,
 382 ) -> &'a Value {
 383     unsafe {
 384         llvm::LLVMConstStructInContext(llcx,
 385                                        elts.as_ptr(), elts.len() as c_uint,
 386                                        packed as Bool)
 387     }
 388 }
 389
 390 #[inline]
 391 fn hi_lo_to_u128(lo: u64, hi: u64) -> u128 {
 392     ((hi as u128) << 64) | (lo as u128)
 393 }