compiler/rustc_codegen_llvm/src/common.rs

   1 //! Code that is useful in various codegen modules.
   2
   3 use crate::consts::{self, const_alloc_to_llvm};
   4 pub use crate::context::CodegenCx;
   5 use crate::llvm::{self, BasicBlock, Bool, ConstantInt, False, OperandBundleDef, True};
   6 use crate::type_::Type;
   7 use crate::type_of::LayoutLlvmExt;
   8 use crate::value::Value;
   9
  10 use rustc_ast::Mutability;
  11 use rustc_codegen_ssa::mir::place::PlaceRef;
  12 use rustc_codegen_ssa::traits::*;
  13 use rustc_middle::bug;
  14 use rustc_middle::mir::interpret::{Allocation, GlobalAlloc, Scalar};
  15 use rustc_middle::ty::{layout::TyAndLayout, ScalarInt};
  16 use rustc_span::symbol::Symbol;
  17 use rustc_target::abi::{self, AddressSpace, HasDataLayout, LayoutOf, Pointer, Size};
  18
  19 use libc::{c_char, c_uint};
  20 use tracing::debug;
  21
  22 /*
  23 * A note on nomenclature of linking: "extern", "foreign", and "upcall".
  24 *
  25 * An "extern" is an LLVM symbol we wind up emitting an undefined external
  26 * reference to. This means "we don't have the thing in this compilation unit,
  27 * please make sure you link it in at runtime". This could be a reference to
  28 * C code found in a C library, or rust code found in a rust crate.
  29 *
  30 * Most "externs" are implicitly declared (automatically) as a result of a
  31 * user declaring an extern _module_ dependency; this causes the rust driver
  32 * to locate an extern crate, scan its compilation metadata, and emit extern
  33 * declarations for any symbols used by the declaring crate.
  34 *
  35 * A "foreign" is an extern that references C (or other non-rust ABI) code.
  36 * There is no metadata to scan for extern references so in these cases either
  37 * a header-digester like bindgen, or manual function prototypes, have to
  38 * serve as declarators. So these are usually given explicitly as prototype
  39 * declarations, in rust code, with ABI attributes on them noting which ABI to
  40 * link via.
  41 *
  42 * An "upcall" is a foreign call generated by the compiler (not corresponding
  43 * to any user-written call in the code) into the runtime library, to perform
  44 * some helper task such as bringing a task to life, allocating memory, etc.
  45 *
  46 */
  47
  48 /// A structure representing an active landing pad for the duration of a basic
  49 /// block.
  50 ///
  51 /// Each `Block` may contain an instance of this, indicating whether the block
  52 /// is part of a landing pad or not. This is used to make decision about whether
  53 /// to emit `invoke` instructions (e.g., in a landing pad we don't continue to
  54 /// use `invoke`) and also about various function call metadata.
  55 ///
  56 /// For GNU exceptions (`landingpad` + `resume` instructions) this structure is
  57 /// just a bunch of `None` instances (not too interesting), but for MSVC
  58 /// exceptions (`cleanuppad` + `cleanupret` instructions) this contains data.
  59 /// When inside of a landing pad, each function call in LLVM IR needs to be
  60 /// annotated with which landing pad it's a part of. This is accomplished via
  61 /// the `OperandBundleDef` value created for MSVC landing pads.
  62 pub struct Funclet<'ll> {
  63     cleanuppad: &'ll Value,
  64     operand: OperandBundleDef<'ll>,
  65 }
  66
  67 impl Funclet<'ll> {
  68     pub fn new(cleanuppad: &'ll Value) -> Self {
  69         Funclet { cleanuppad, operand: OperandBundleDef::new("funclet", &[cleanuppad]) }
  70     }
  71
  72     pub fn cleanuppad(&self) -> &'ll Value {
  73         self.cleanuppad
  74     }
  75
  76     pub fn bundle(&self) -> &OperandBundleDef<'ll> {
  77         &self.operand
  78     }
  79 }
  80
  81 impl BackendTypes for CodegenCx<'ll, 'tcx> {
  82     type Value = &'ll Value;
  83     // FIXME(eddyb) replace this with a `Function` "subclass" of `Value`.
  84     type Function = &'ll Value;
  85
  86     type BasicBlock = &'ll BasicBlock;
  87     type Type = &'ll Type;
  88     type Funclet = Funclet<'ll>;
  89
  90     type DIScope = &'ll llvm::debuginfo::DIScope;
  91     type DILocation = &'ll llvm::debuginfo::DILocation;
  92     type DIVariable = &'ll llvm::debuginfo::DIVariable;
  93 }
  94
  95 impl CodegenCx<'ll, 'tcx> {
  96     pub fn const_array(&self, ty: &'ll Type, elts: &[&'ll Value]) -> &'ll Value {
  97         unsafe { llvm::LLVMConstArray(ty, elts.as_ptr(), elts.len() as c_uint) }
  98     }
  99
 100     pub fn const_vector(&self, elts: &[&'ll Value]) -> &'ll Value {
 101         unsafe { llvm::LLVMConstVector(elts.as_ptr(), elts.len() as c_uint) }
 102     }
 103
 104     pub fn const_bytes(&self, bytes: &[u8]) -> &'ll Value {
 105         bytes_in_context(self.llcx, bytes)
 106     }
 107
 108     fn const_cstr(&self, s: Symbol, null_terminated: bool) -> &'ll Value {
 109         unsafe {
 110             if let Some(&llval) = self.const_cstr_cache.borrow().get(&s) {
 111                 return llval;
 112             }
 113
 114             let s_str = s.as_str();
 115             let sc = llvm::LLVMConstStringInContext(
 116                 self.llcx,
 117                 s_str.as_ptr() as *const c_char,
 118                 s_str.len() as c_uint,
 119                 !null_terminated as Bool,
 120             );
 121             let sym = self.generate_local_symbol_name("str");
 122             let g = self.define_global(&sym[..], self.val_ty(sc)).unwrap_or_else(|| {
 123                 bug!("symbol `{}` is already defined", sym);
 124             });
 125             llvm::LLVMSetInitializer(g, sc);
 126             llvm::LLVMSetGlobalConstant(g, True);
 127             llvm::LLVMRustSetLinkage(g, llvm::Linkage::InternalLinkage);
 128
 129             self.const_cstr_cache.borrow_mut().insert(s, g);
 130             g
 131         }
 132     }
 133
 134     pub fn const_get_elt(&self, v: &'ll Value, idx: u64) -> &'ll Value {
 135         unsafe {
 136             assert_eq!(idx as c_uint as u64, idx);
 137             let us = &[idx as c_uint];
 138             let r = llvm::LLVMConstExtractValue(v, us.as_ptr(), us.len() as c_uint);
 139
 140             debug!("const_get_elt(v={:?}, idx={}, r={:?})", v, idx, r);
 141
 142             r
 143         }
 144     }
 145 }
 146
 147 impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 148     fn const_null(&self, t: &'ll Type) -> &'ll Value {
 149         unsafe { llvm::LLVMConstNull(t) }
 150     }
 151
 152     fn const_undef(&self, t: &'ll Type) -> &'ll Value {
 153         unsafe { llvm::LLVMGetUndef(t) }
 154     }
 155
 156     fn const_int(&self, t: &'ll Type, i: i64) -> &'ll Value {
 157         unsafe { llvm::LLVMConstInt(t, i as u64, True) }
 158     }
 159
 160     fn const_uint(&self, t: &'ll Type, i: u64) -> &'ll Value {
 161         unsafe { llvm::LLVMConstInt(t, i, False) }
 162     }
 163
 164     fn const_uint_big(&self, t: &'ll Type, u: u128) -> &'ll Value {
 165         unsafe {
 166             let words = [u as u64, (u >> 64) as u64];
 167             llvm::LLVMConstIntOfArbitraryPrecision(t, 2, words.as_ptr())
 168         }
 169     }
 170
 171     fn const_bool(&self, val: bool) -> &'ll Value {
 172         self.const_uint(self.type_i1(), val as u64)
 173     }
 174
 175     fn const_i32(&self, i: i32) -> &'ll Value {
 176         self.const_int(self.type_i32(), i as i64)
 177     }
 178
 179     fn const_u32(&self, i: u32) -> &'ll Value {
 180         self.const_uint(self.type_i32(), i as u64)
 181     }
 182
 183     fn const_u64(&self, i: u64) -> &'ll Value {
 184         self.const_uint(self.type_i64(), i)
 185     }
 186
 187     fn const_usize(&self, i: u64) -> &'ll Value {
 188         let bit_size = self.data_layout().pointer_size.bits();
 189         if bit_size < 64 {
 190             // make sure it doesn't overflow
 191             assert!(i < (1 << bit_size));
 192         }
 193
 194         self.const_uint(self.isize_ty, i)
 195     }
 196
 197     fn const_u8(&self, i: u8) -> &'ll Value {
 198         self.const_uint(self.type_i8(), i as u64)
 199     }
 200
 201     fn const_real(&self, t: &'ll Type, val: f64) -> &'ll Value {
 202         unsafe { llvm::LLVMConstReal(t, val) }
 203     }
 204
 205     fn const_str(&self, s: Symbol) -> (&'ll Value, &'ll Value) {
 206         let len = s.as_str().len();
 207         let cs = consts::ptrcast(
 208             self.const_cstr(s, false),
 209             self.type_ptr_to(self.layout_of(self.tcx.types.str_).llvm_type(self)),
 210         );
 211         (cs, self.const_usize(len as u64))
 212     }
 213
 214     fn const_struct(&self, elts: &[&'ll Value], packed: bool) -> &'ll Value {
 215         struct_in_context(self.llcx, elts, packed)
 216     }
 217
 218     fn const_to_opt_uint(&self, v: &'ll Value) -> Option<u64> {
 219         try_as_const_integral(v).map(|v| unsafe { llvm::LLVMConstIntGetZExtValue(v) })
 220     }
 221
 222     fn const_to_opt_u128(&self, v: &'ll Value, sign_ext: bool) -> Option<u128> {
 223         try_as_const_integral(v).and_then(|v| unsafe {
 224             let (mut lo, mut hi) = (0u64, 0u64);
 225             let success = llvm::LLVMRustConstInt128Get(v, sign_ext, &mut hi, &mut lo);
 226             success.then_some(hi_lo_to_u128(lo, hi))
 227         })
 228     }
 229
 230     fn scalar_to_backend(&self, cv: Scalar, layout: &abi::Scalar, llty: &'ll Type) -> &'ll Value {
 231         let bitsize = if layout.is_bool() { 1 } else { layout.value.size(self).bits() };
 232         match cv {
 233             Scalar::Int(ScalarInt::ZST) => {
 234                 assert_eq!(0, layout.value.size(self).bytes());
 235                 self.const_undef(self.type_ix(0))
 236             }
 237             Scalar::Int(int) => {
 238                 let data = int.assert_bits(layout.value.size(self));
 239                 let llval = self.const_uint_big(self.type_ix(bitsize), data);
 240                 if layout.value == Pointer {
 241                     unsafe { llvm::LLVMConstIntToPtr(llval, llty) }
 242                 } else {
 243                     self.const_bitcast(llval, llty)
 244                 }
 245             }
 246             Scalar::Ptr(ptr) => {
 247                 let (base_addr, base_addr_space) = match self.tcx.global_alloc(ptr.alloc_id) {
 248                     GlobalAlloc::Memory(alloc) => {
 249                         let init = const_alloc_to_llvm(self, alloc);
 250                         let value = match alloc.mutability {
 251                             Mutability::Mut => self.static_addr_of_mut(init, alloc.align, None),
 252                             _ => self.static_addr_of(init, alloc.align, None),
 253                         };
 254                         if !self.sess().fewer_names() {
 255                             llvm::set_value_name(value, format!("{:?}", ptr.alloc_id).as_bytes());
 256                         }
 257                         (value, AddressSpace::DATA)
 258                     }
 259                     GlobalAlloc::Function(fn_instance) => (
 260                         self.get_fn_addr(fn_instance.polymorphize(self.tcx)),
 261                         self.data_layout().instruction_address_space,
 262                     ),
 263                     GlobalAlloc::Static(def_id) => {
 264                         assert!(self.tcx.is_static(def_id));
 265                         assert!(!self.tcx.is_thread_local_static(def_id));
 266                         (self.get_static(def_id), AddressSpace::DATA)
 267                     }
 268                 };
 269                 let llval = unsafe {
 270                     llvm::LLVMConstInBoundsGEP(
 271                         self.const_bitcast(base_addr, self.type_i8p_ext(base_addr_space)),
 272                         &self.const_usize(ptr.offset.bytes()),
 273                         1,
 274                     )
 275                 };
 276                 if layout.value != Pointer {
 277                     unsafe { llvm::LLVMConstPtrToInt(llval, llty) }
 278                 } else {
 279                     self.const_bitcast(llval, llty)
 280                 }
 281             }
 282         }
 283     }
 284
 285     fn from_const_alloc(
 286         &self,
 287         layout: TyAndLayout<'tcx>,
 288         alloc: &Allocation,
 289         offset: Size,
 290     ) -> PlaceRef<'tcx, &'ll Value> {
 291         assert_eq!(alloc.align, layout.align.abi);
 292         let llty = self.type_ptr_to(layout.llvm_type(self));
 293         let llval = if layout.size == Size::ZERO {
 294             let llval = self.const_usize(alloc.align.bytes());
 295             unsafe { llvm::LLVMConstIntToPtr(llval, llty) }
 296         } else {
 297             let init = const_alloc_to_llvm(self, alloc);
 298             let base_addr = self.static_addr_of(init, alloc.align, None);
 299
 300             let llval = unsafe {
 301                 llvm::LLVMConstInBoundsGEP(
 302                     self.const_bitcast(base_addr, self.type_i8p()),
 303                     &self.const_usize(offset.bytes()),
 304                     1,
 305                 )
 306             };
 307             self.const_bitcast(llval, llty)
 308         };
 309         PlaceRef::new_sized(llval, layout)
 310     }
 311
 312     fn const_ptrcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value {
 313         consts::ptrcast(val, ty)
 314     }
 315 }
 316
 317 /// Get the [LLVM type][Type] of a [`Value`].
 318 pub fn val_ty(v: &Value) -> &Type {
 319     unsafe { llvm::LLVMTypeOf(v) }
 320 }
 321
 322 pub fn bytes_in_context(llcx: &'ll llvm::Context, bytes: &[u8]) -> &'ll Value {
 323     unsafe {
 324         let ptr = bytes.as_ptr() as *const c_char;
 325         llvm::LLVMConstStringInContext(llcx, ptr, bytes.len() as c_uint, True)
 326     }
 327 }
 328
 329 pub fn struct_in_context(llcx: &'a llvm::Context, elts: &[&'a Value], packed: bool) -> &'a Value {
 330     unsafe {
 331         llvm::LLVMConstStructInContext(llcx, elts.as_ptr(), elts.len() as c_uint, packed as Bool)
 332     }
 333 }
 334
 335 #[inline]
 336 fn hi_lo_to_u128(lo: u64, hi: u64) -> u128 {
 337     ((hi as u128) << 64) | (lo as u128)
 338 }
 339
 340 fn try_as_const_integral(v: &Value) -> Option<&ConstantInt> {
 341     unsafe { llvm::LLVMIsAConstantInt(v) }
 342 }