src/intrinsic/mod.rs

   1 pub mod llvm;
   2 mod simd;
   3
   4 use gccjit::{ComparisonOp, Function, RValue, ToRValue, Type, UnaryOp, FunctionType};
   5 use rustc_codegen_ssa::MemFlags;
   6 use rustc_codegen_ssa::base::wants_msvc_seh;
   7 use rustc_codegen_ssa::common::{IntPredicate, span_invalid_monomorphization_error};
   8 use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
   9 use rustc_codegen_ssa::mir::place::PlaceRef;
  10 use rustc_codegen_ssa::traits::{ArgAbiMethods, BaseTypeMethods, BuilderMethods, ConstMethods, IntrinsicCallMethods};
  11 use rustc_middle::bug;
  12 use rustc_middle::ty::{self, Instance, Ty};
  13 use rustc_middle::ty::layout::LayoutOf;
  14 use rustc_span::{Span, Symbol, symbol::kw, sym};
  15 use rustc_target::abi::HasDataLayout;
  16 use rustc_target::abi::call::{ArgAbi, FnAbi, PassMode};
  17 use rustc_target::spec::PanicStrategy;
  18
  19 use crate::abi::GccType;
  20 use crate::builder::Builder;
  21 use crate::common::{SignType, TypeReflection};
  22 use crate::context::CodegenCx;
  23 use crate::type_of::LayoutGccExt;
  24 use crate::intrinsic::simd::generic_simd_intrinsic;
  25
  26 fn get_simple_intrinsic<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, name: Symbol) -> Option<Function<'gcc>> {
  27     let gcc_name = match name {
  28         sym::sqrtf32 => "sqrtf",
  29         sym::sqrtf64 => "sqrt",
  30         sym::powif32 => "__builtin_powif",
  31         sym::powif64 => "__builtin_powi",
  32         sym::sinf32 => "sinf",
  33         sym::sinf64 => "sin",
  34         sym::cosf32 => "cosf",
  35         sym::cosf64 => "cos",
  36         sym::powf32 => "powf",
  37         sym::powf64 => "pow",
  38         sym::expf32 => "expf",
  39         sym::expf64 => "exp",
  40         sym::exp2f32 => "exp2f",
  41         sym::exp2f64 => "exp2",
  42         sym::logf32 => "logf",
  43         sym::logf64 => "log",
  44         sym::log10f32 => "log10f",
  45         sym::log10f64 => "log10",
  46         sym::log2f32 => "log2f",
  47         sym::log2f64 => "log2",
  48         sym::fmaf32 => "fmaf",
  49         sym::fmaf64 => "fma",
  50         sym::fabsf32 => "fabsf",
  51         sym::fabsf64 => "fabs",
  52         sym::minnumf32 => "fminf",
  53         sym::minnumf64 => "fmin",
  54         sym::maxnumf32 => "fmaxf",
  55         sym::maxnumf64 => "fmax",
  56         sym::copysignf32 => "copysignf",
  57         sym::copysignf64 => "copysign",
  58         sym::floorf32 => "floorf",
  59         sym::floorf64 => "floor",
  60         sym::ceilf32 => "ceilf",
  61         sym::ceilf64 => "ceil",
  62         sym::truncf32 => "truncf",
  63         sym::truncf64 => "trunc",
  64         sym::rintf32 => "rintf",
  65         sym::rintf64 => "rint",
  66         sym::nearbyintf32 => "nearbyintf",
  67         sym::nearbyintf64 => "nearbyint",
  68         sym::roundf32 => "roundf",
  69         sym::roundf64 => "round",
  70         sym::abort => "abort",
  71         _ => return None,
  72     };
  73     Some(cx.context.get_builtin_function(&gcc_name))
  74 }
  75
  76 impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
  77     fn codegen_intrinsic_call(&mut self, instance: Instance<'tcx>, fn_abi: &FnAbi<'tcx, Ty<'tcx>>, args: &[OperandRef<'tcx, RValue<'gcc>>], llresult: RValue<'gcc>, span: Span) {
  78         let tcx = self.tcx;
  79         let callee_ty = instance.ty(tcx, ty::ParamEnv::reveal_all());
  80
  81         let (def_id, substs) = match *callee_ty.kind() {
  82             ty::FnDef(def_id, substs) => (def_id, substs),
  83             _ => bug!("expected fn item type, found {}", callee_ty),
  84         };
  85
  86         let sig = callee_ty.fn_sig(tcx);
  87         let sig = tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig);
  88         let arg_tys = sig.inputs();
  89         let ret_ty = sig.output();
  90         let name = tcx.item_name(def_id);
  91         let name_str = name.as_str();
  92
  93         let llret_ty = self.layout_of(ret_ty).gcc_type(self, true);
  94         let result = PlaceRef::new_sized(llresult, fn_abi.ret.layout);
  95
  96         let simple = get_simple_intrinsic(self, name);
  97         let llval =
  98             match name {
  99                 _ if simple.is_some() => {
 100                     // FIXME(antoyo): remove this cast when the API supports function.
 101                     let func = unsafe { std::mem::transmute(simple.expect("simple")) };
 102                     self.call(self.type_void(), func, &args.iter().map(|arg| arg.immediate()).collect::<Vec<_>>(), None)
 103                 },
 104                 sym::likely => {
 105                     self.expect(args[0].immediate(), true)
 106                 }
 107                 sym::unlikely => {
 108                     self.expect(args[0].immediate(), false)
 109                 }
 110                 kw::Try => {
 111                     try_intrinsic(
 112                         self,
 113                         args[0].immediate(),
 114                         args[1].immediate(),
 115                         args[2].immediate(),
 116                         llresult,
 117                     );
 118                     return;
 119                 }
 120                 sym::breakpoint => {
 121                     unimplemented!();
 122                 }
 123                 sym::va_copy => {
 124                     unimplemented!();
 125                 }
 126                 sym::va_arg => {
 127                     unimplemented!();
 128                 }
 129
 130                 sym::volatile_load | sym::unaligned_volatile_load => {
 131                     let tp_ty = substs.type_at(0);
 132                     let mut ptr = args[0].immediate();
 133                     if let PassMode::Cast(ty) = fn_abi.ret.mode {
 134                         ptr = self.pointercast(ptr, self.type_ptr_to(ty.gcc_type(self)));
 135                     }
 136                     let load = self.volatile_load(ptr.get_type(), ptr);
 137                     // TODO(antoyo): set alignment.
 138                     self.to_immediate(load, self.layout_of(tp_ty))
 139                 }
 140                 sym::volatile_store => {
 141                     let dst = args[0].deref(self.cx());
 142                     args[1].val.volatile_store(self, dst);
 143                     return;
 144                 }
 145                 sym::unaligned_volatile_store => {
 146                     let dst = args[0].deref(self.cx());
 147                     args[1].val.unaligned_volatile_store(self, dst);
 148                     return;
 149                 }
 150                 sym::prefetch_read_data
 151                     | sym::prefetch_write_data
 152                     | sym::prefetch_read_instruction
 153                     | sym::prefetch_write_instruction => {
 154                         unimplemented!();
 155                     }
 156                 sym::ctlz
 157                     | sym::ctlz_nonzero
 158                     | sym::cttz
 159                     | sym::cttz_nonzero
 160                     | sym::ctpop
 161                     | sym::bswap
 162                     | sym::bitreverse
 163                     | sym::rotate_left
 164                     | sym::rotate_right
 165                     | sym::saturating_add
 166                     | sym::saturating_sub => {
 167                         let ty = arg_tys[0];
 168                         match int_type_width_signed(ty, self) {
 169                             Some((width, signed)) => match name {
 170                                 sym::ctlz | sym::cttz => {
 171                                     let func = self.current_func.borrow().expect("func");
 172                                     let then_block = func.new_block("then");
 173                                     let else_block = func.new_block("else");
 174                                     let after_block = func.new_block("after");
 175
 176                                     let arg = args[0].immediate();
 177                                     let result = func.new_local(None, arg.get_type(), "zeros");
 178                                     let zero = self.cx.gcc_zero(arg.get_type());
 179                                     let cond = self.gcc_icmp(IntPredicate::IntEQ, arg, zero);
 180                                     self.llbb().end_with_conditional(None, cond, then_block, else_block);
 181
 182                                     let zero_result = self.cx.gcc_uint(arg.get_type(), width);
 183                                     then_block.add_assignment(None, result, zero_result);
 184                                     then_block.end_with_jump(None, after_block);
 185
 186                                     // NOTE: since jumps were added in a place
 187                                     // count_leading_zeroes() does not expect, the current block
 188                                     // in the state need to be updated.
 189                                     self.switch_to_block(else_block);
 190
 191                                     let zeros =
 192                                         match name {
 193                                             sym::ctlz => self.count_leading_zeroes(width, arg),
 194                                             sym::cttz => self.count_trailing_zeroes(width, arg),
 195                                             _ => unreachable!(),
 196                                         };
 197                                     self.llbb().add_assignment(None, result, zeros);
 198                                     self.llbb().end_with_jump(None, after_block);
 199
 200                                     // NOTE: since jumps were added in a place rustc does not
 201                                     // expect, the current block in the state need to be updated.
 202                                     self.switch_to_block(after_block);
 203
 204                                     result.to_rvalue()
 205                                 }
 206                                 sym::ctlz_nonzero => {
 207                                     self.count_leading_zeroes(width, args[0].immediate())
 208                                 },
 209                                 sym::cttz_nonzero => {
 210                                     self.count_trailing_zeroes(width, args[0].immediate())
 211                                 }
 212                                 sym::ctpop => self.pop_count(args[0].immediate()),
 213                                 sym::bswap => {
 214                                     if width == 8 {
 215                                         args[0].immediate() // byte swap a u8/i8 is just a no-op
 216                                     }
 217                                     else {
 218                                         self.gcc_bswap(args[0].immediate(), width)
 219                                     }
 220                                 },
 221                                 sym::bitreverse => self.bit_reverse(width, args[0].immediate()),
 222                                 sym::rotate_left | sym::rotate_right => {
 223                                     // TODO(antoyo): implement using algorithm from:
 224                                     // https://blog.regehr.org/archives/1063
 225                                     // for other platforms.
 226                                     let is_left = name == sym::rotate_left;
 227                                     let val = args[0].immediate();
 228                                     let raw_shift = args[1].immediate();
 229                                     if is_left {
 230                                         self.rotate_left(val, raw_shift, width)
 231                                     }
 232                                     else {
 233                                         self.rotate_right(val, raw_shift, width)
 234                                     }
 235                                 },
 236                                 sym::saturating_add => {
 237                                     self.saturating_add(args[0].immediate(), args[1].immediate(), signed, width)
 238                                 },
 239                                 sym::saturating_sub => {
 240                                     self.saturating_sub(args[0].immediate(), args[1].immediate(), signed, width)
 241                                 },
 242                                 _ => bug!(),
 243                             },
 244                             None => {
 245                                 span_invalid_monomorphization_error(
 246                                     tcx.sess,
 247                                     span,
 248                                     &format!(
 249                                         "invalid monomorphization of `{}` intrinsic: \
 250                                       expected basic integer type, found `{}`",
 251                                       name, ty
 252                                     ),
 253                                 );
 254                                 return;
 255                             }
 256                         }
 257                     }
 258
 259                 sym::raw_eq => {
 260                     use rustc_target::abi::Abi::*;
 261                     let tp_ty = substs.type_at(0);
 262                     let layout = self.layout_of(tp_ty).layout;
 263                     let _use_integer_compare = match layout.abi() {
 264                         Scalar(_) | ScalarPair(_, _) => true,
 265                         Uninhabited | Vector { .. } => false,
 266                         Aggregate { .. } => {
 267                             // For rusty ABIs, small aggregates are actually passed
 268                             // as `RegKind::Integer` (see `FnAbi::adjust_for_abi`),
 269                             // so we re-use that same threshold here.
 270                             layout.size() <= self.data_layout().pointer_size * 2
 271                         }
 272                     };
 273
 274                     let a = args[0].immediate();
 275                     let b = args[1].immediate();
 276                     if layout.size().bytes() == 0 {
 277                         self.const_bool(true)
 278                     }
 279                     /*else if use_integer_compare {
 280                         let integer_ty = self.type_ix(layout.size.bits()); // FIXME(antoyo): LLVM creates an integer of 96 bits for [i32; 3], but gcc doesn't support this, so it creates an integer of 128 bits.
 281                         let ptr_ty = self.type_ptr_to(integer_ty);
 282                         let a_ptr = self.bitcast(a, ptr_ty);
 283                         let a_val = self.load(integer_ty, a_ptr, layout.align.abi);
 284                         let b_ptr = self.bitcast(b, ptr_ty);
 285                         let b_val = self.load(integer_ty, b_ptr, layout.align.abi);
 286                         self.icmp(IntPredicate::IntEQ, a_val, b_val)
 287                     }*/
 288                     else {
 289                         let void_ptr_type = self.context.new_type::<*const ()>();
 290                         let a_ptr = self.bitcast(a, void_ptr_type);
 291                         let b_ptr = self.bitcast(b, void_ptr_type);
 292                         let n = self.context.new_cast(None, self.const_usize(layout.size().bytes()), self.sizet_type);
 293                         let builtin = self.context.get_builtin_function("memcmp");
 294                         let cmp = self.context.new_call(None, builtin, &[a_ptr, b_ptr, n]);
 295                         self.icmp(IntPredicate::IntEQ, cmp, self.const_i32(0))
 296                     }
 297                 }
 298
 299                 sym::black_box => {
 300                     args[0].val.store(self, result);
 301
 302                     let block = self.llbb();
 303                     let extended_asm = block.add_extended_asm(None, "");
 304                     extended_asm.add_input_operand(None, "r", result.llval);
 305                     extended_asm.add_clobber("memory");
 306                     extended_asm.set_volatile_flag(true);
 307
 308                     // We have copied the value to `result` already.
 309                     return;
 310                 }
 311
 312                 _ if name_str.starts_with("simd_") => {
 313                     match generic_simd_intrinsic(self, name, callee_ty, args, ret_ty, llret_ty, span) {
 314                         Ok(llval) => llval,
 315                         Err(()) => return,
 316                     }
 317                 }
 318
 319                 _ => bug!("unknown intrinsic '{}'", name),
 320             };
 321
 322         if !fn_abi.ret.is_ignore() {
 323             if let PassMode::Cast(ty) = fn_abi.ret.mode {
 324                 let ptr_llty = self.type_ptr_to(ty.gcc_type(self));
 325                 let ptr = self.pointercast(result.llval, ptr_llty);
 326                 self.store(llval, ptr, result.align);
 327             }
 328             else {
 329                 OperandRef::from_immediate_or_packed_pair(self, llval, result.layout)
 330                     .val
 331                     .store(self, result);
 332             }
 333         }
 334     }
 335
 336     fn abort(&mut self) {
 337         let func = self.context.get_builtin_function("abort");
 338         let func: RValue<'gcc> = unsafe { std::mem::transmute(func) };
 339         self.call(self.type_void(), func, &[], None);
 340     }
 341
 342     fn assume(&mut self, value: Self::Value) {
 343         // TODO(antoyo): switch to assume when it exists.
 344         // Or use something like this:
 345         // #define __assume(cond) do { if (!(cond)) __builtin_unreachable(); } while (0)
 346         self.expect(value, true);
 347     }
 348
 349     fn expect(&mut self, cond: Self::Value, _expected: bool) -> Self::Value {
 350         // TODO(antoyo)
 351         cond
 352     }
 353
 354     fn type_test(&mut self, _pointer: Self::Value, _typeid: Self::Value) -> Self::Value {
 355         // Unsupported.
 356         self.context.new_rvalue_from_int(self.int_type, 0)
 357     }
 358
 359     fn va_start(&mut self, _va_list: RValue<'gcc>) -> RValue<'gcc> {
 360         unimplemented!();
 361     }
 362
 363     fn va_end(&mut self, _va_list: RValue<'gcc>) -> RValue<'gcc> {
 364         unimplemented!();
 365     }
 366 }
 367
 368 impl<'a, 'gcc, 'tcx> ArgAbiMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
 369     fn store_fn_arg(&mut self, arg_abi: &ArgAbi<'tcx, Ty<'tcx>>, idx: &mut usize, dst: PlaceRef<'tcx, Self::Value>) {
 370         arg_abi.store_fn_arg(self, idx, dst)
 371     }
 372
 373     fn store_arg(&mut self, arg_abi: &ArgAbi<'tcx, Ty<'tcx>>, val: RValue<'gcc>, dst: PlaceRef<'tcx, RValue<'gcc>>) {
 374         arg_abi.store(self, val, dst)
 375     }
 376
 377     fn arg_memory_ty(&self, arg_abi: &ArgAbi<'tcx, Ty<'tcx>>) -> Type<'gcc> {
 378         arg_abi.memory_ty(self)
 379     }
 380 }
 381
 382 pub trait ArgAbiExt<'gcc, 'tcx> {
 383     fn memory_ty(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc>;
 384     fn store(&self, bx: &mut Builder<'_, 'gcc, 'tcx>, val: RValue<'gcc>, dst: PlaceRef<'tcx, RValue<'gcc>>);
 385     fn store_fn_arg(&self, bx: &mut Builder<'_, 'gcc, 'tcx>, idx: &mut usize, dst: PlaceRef<'tcx, RValue<'gcc>>);
 386 }
 387
 388 impl<'gcc, 'tcx> ArgAbiExt<'gcc, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
 389     /// Gets the LLVM type for a place of the original Rust type of
 390     /// this argument/return, i.e., the result of `type_of::type_of`.
 391     fn memory_ty(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc> {
 392         self.layout.gcc_type(cx, true)
 393     }
 394
 395     /// Stores a direct/indirect value described by this ArgAbi into a
 396     /// place for the original Rust type of this argument/return.
 397     /// Can be used for both storing formal arguments into Rust variables
 398     /// or results of call/invoke instructions into their destinations.
 399     fn store(&self, bx: &mut Builder<'_, 'gcc, 'tcx>, val: RValue<'gcc>, dst: PlaceRef<'tcx, RValue<'gcc>>) {
 400         if self.is_ignore() {
 401             return;
 402         }
 403         if self.is_sized_indirect() {
 404             OperandValue::Ref(val, None, self.layout.align.abi).store(bx, dst)
 405         }
 406         else if self.is_unsized_indirect() {
 407             bug!("unsized `ArgAbi` must be handled through `store_fn_arg`");
 408         }
 409         else if let PassMode::Cast(cast) = self.mode {
 410             // FIXME(eddyb): Figure out when the simpler Store is safe, clang
 411             // uses it for i16 -> {i8, i8}, but not for i24 -> {i8, i8, i8}.
 412             let can_store_through_cast_ptr = false;
 413             if can_store_through_cast_ptr {
 414                 let cast_ptr_llty = bx.type_ptr_to(cast.gcc_type(bx));
 415                 let cast_dst = bx.pointercast(dst.llval, cast_ptr_llty);
 416                 bx.store(val, cast_dst, self.layout.align.abi);
 417             }
 418             else {
 419                 // The actual return type is a struct, but the ABI
 420                 // adaptation code has cast it into some scalar type.  The
 421                 // code that follows is the only reliable way I have
 422                 // found to do a transform like i64 -> {i32,i32}.
 423                 // Basically we dump the data onto the stack then memcpy it.
 424                 //
 425                 // Other approaches I tried:
 426                 // - Casting rust ret pointer to the foreign type and using Store
 427                 //   is (a) unsafe if size of foreign type > size of rust type and
 428                 //   (b) runs afoul of strict aliasing rules, yielding invalid
 429                 //   assembly under -O (specifically, the store gets removed).
 430                 // - Truncating foreign type to correct integral type and then
 431                 //   bitcasting to the struct type yields invalid cast errors.
 432
 433                 // We instead thus allocate some scratch space...
 434                 let scratch_size = cast.size(bx);
 435                 let scratch_align = cast.align(bx);
 436                 let llscratch = bx.alloca(cast.gcc_type(bx), scratch_align);
 437                 bx.lifetime_start(llscratch, scratch_size);
 438
 439                 // ... where we first store the value...
 440                 bx.store(val, llscratch, scratch_align);
 441
 442                 // ... and then memcpy it to the intended destination.
 443                 bx.memcpy(
 444                     dst.llval,
 445                     self.layout.align.abi,
 446                     llscratch,
 447                     scratch_align,
 448                     bx.const_usize(self.layout.size.bytes()),
 449                     MemFlags::empty(),
 450                 );
 451
 452                 bx.lifetime_end(llscratch, scratch_size);
 453             }
 454         }
 455         else {
 456             OperandValue::Immediate(val).store(bx, dst);
 457         }
 458     }
 459
 460     fn store_fn_arg<'a>(&self, bx: &mut Builder<'a, 'gcc, 'tcx>, idx: &mut usize, dst: PlaceRef<'tcx, RValue<'gcc>>) {
 461         let mut next = || {
 462             let val = bx.current_func().get_param(*idx as i32);
 463             *idx += 1;
 464             val.to_rvalue()
 465         };
 466         match self.mode {
 467             PassMode::Ignore => {},
 468             PassMode::Pair(..) => {
 469                 OperandValue::Pair(next(), next()).store(bx, dst);
 470             },
 471             PassMode::Indirect { extra_attrs: Some(_), .. } => {
 472                 OperandValue::Ref(next(), Some(next()), self.layout.align.abi).store(bx, dst);
 473             },
 474             PassMode::Direct(_) | PassMode::Indirect { extra_attrs: None, .. } | PassMode::Cast(_) => {
 475                 let next_arg = next();
 476                 self.store(bx, next_arg, dst);
 477             },
 478         }
 479     }
 480 }
 481
 482 fn int_type_width_signed<'gcc, 'tcx>(ty: Ty<'tcx>, cx: &CodegenCx<'gcc, 'tcx>) -> Option<(u64, bool)> {
 483     match ty.kind() {
 484         ty::Int(t) => Some((
 485             match t {
 486                 rustc_middle::ty::IntTy::Isize => u64::from(cx.tcx.sess.target.pointer_width),
 487                 rustc_middle::ty::IntTy::I8 => 8,
 488                 rustc_middle::ty::IntTy::I16 => 16,
 489                 rustc_middle::ty::IntTy::I32 => 32,
 490                 rustc_middle::ty::IntTy::I64 => 64,
 491                 rustc_middle::ty::IntTy::I128 => 128,
 492             },
 493             true,
 494         )),
 495         ty::Uint(t) => Some((
 496             match t {
 497                 rustc_middle::ty::UintTy::Usize => u64::from(cx.tcx.sess.target.pointer_width),
 498                 rustc_middle::ty::UintTy::U8 => 8,
 499                 rustc_middle::ty::UintTy::U16 => 16,
 500                 rustc_middle::ty::UintTy::U32 => 32,
 501                 rustc_middle::ty::UintTy::U64 => 64,
 502                 rustc_middle::ty::UintTy::U128 => 128,
 503             },
 504             false,
 505         )),
 506         _ => None,
 507     }
 508 }
 509
 510 impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
 511     fn bit_reverse(&mut self, width: u64, value: RValue<'gcc>) -> RValue<'gcc> {
 512         let result_type = value.get_type();
 513         let typ = result_type.to_unsigned(self.cx);
 514
 515         let value =
 516             if result_type.is_signed(self.cx) {
 517                 self.gcc_int_cast(value, typ)
 518             }
 519             else {
 520                 value
 521             };
 522
 523         let context = &self.cx.context;
 524         let result =
 525             match width {
 526                 8 => {
 527                     // First step.
 528                     let left = self.and(value, context.new_rvalue_from_int(typ, 0xF0));
 529                     let left = self.lshr(left, context.new_rvalue_from_int(typ, 4));
 530                     let right = self.and(value, context.new_rvalue_from_int(typ, 0x0F));
 531                     let right = self.shl(right, context.new_rvalue_from_int(typ, 4));
 532                     let step1 = self.or(left, right);
 533
 534                     // Second step.
 535                     let left = self.and(step1, context.new_rvalue_from_int(typ, 0xCC));
 536                     let left = self.lshr(left, context.new_rvalue_from_int(typ, 2));
 537                     let right = self.and(step1, context.new_rvalue_from_int(typ, 0x33));
 538                     let right = self.shl(right, context.new_rvalue_from_int(typ, 2));
 539                     let step2 = self.or(left, right);
 540
 541                     // Third step.
 542                     let left = self.and(step2, context.new_rvalue_from_int(typ, 0xAA));
 543                     let left = self.lshr(left, context.new_rvalue_from_int(typ, 1));
 544                     let right = self.and(step2, context.new_rvalue_from_int(typ, 0x55));
 545                     let right = self.shl(right, context.new_rvalue_from_int(typ, 1));
 546                     let step3 = self.or(left, right);
 547
 548                     step3
 549                 },
 550                 16 => {
 551                     // First step.
 552                     let left = self.and(value, context.new_rvalue_from_int(typ, 0x5555));
 553                     let left = self.shl(left, context.new_rvalue_from_int(typ, 1));
 554                     let right = self.and(value, context.new_rvalue_from_int(typ, 0xAAAA));
 555                     let right = self.lshr(right, context.new_rvalue_from_int(typ, 1));
 556                     let step1 = self.or(left, right);
 557
 558                     // Second step.
 559                     let left = self.and(step1, context.new_rvalue_from_int(typ, 0x3333));
 560                     let left = self.shl(left, context.new_rvalue_from_int(typ, 2));
 561                     let right = self.and(step1, context.new_rvalue_from_int(typ, 0xCCCC));
 562                     let right = self.lshr(right, context.new_rvalue_from_int(typ, 2));
 563                     let step2 = self.or(left, right);
 564
 565                     // Third step.
 566                     let left = self.and(step2, context.new_rvalue_from_int(typ, 0x0F0F));
 567                     let left = self.shl(left, context.new_rvalue_from_int(typ, 4));
 568                     let right = self.and(step2, context.new_rvalue_from_int(typ, 0xF0F0));
 569                     let right = self.lshr(right, context.new_rvalue_from_int(typ, 4));
 570                     let step3 = self.or(left, right);
 571
 572                     // Fourth step.
 573                     let left = self.and(step3, context.new_rvalue_from_int(typ, 0x00FF));
 574                     let left = self.shl(left, context.new_rvalue_from_int(typ, 8));
 575                     let right = self.and(step3, context.new_rvalue_from_int(typ, 0xFF00));
 576                     let right = self.lshr(right, context.new_rvalue_from_int(typ, 8));
 577                     let step4 = self.or(left, right);
 578
 579                     step4
 580                 },
 581                 32 => {
 582                     // TODO(antoyo): Refactor with other implementations.
 583                     // First step.
 584                     let left = self.and(value, context.new_rvalue_from_long(typ, 0x55555555));
 585                     let left = self.shl(left, context.new_rvalue_from_long(typ, 1));
 586                     let right = self.and(value, context.new_rvalue_from_long(typ, 0xAAAAAAAA));
 587                     let right = self.lshr(right, context.new_rvalue_from_long(typ, 1));
 588                     let step1 = self.or(left, right);
 589
 590                     // Second step.
 591                     let left = self.and(step1, context.new_rvalue_from_long(typ, 0x33333333));
 592                     let left = self.shl(left, context.new_rvalue_from_long(typ, 2));
 593                     let right = self.and(step1, context.new_rvalue_from_long(typ, 0xCCCCCCCC));
 594                     let right = self.lshr(right, context.new_rvalue_from_long(typ, 2));
 595                     let step2 = self.or(left, right);
 596
 597                     // Third step.
 598                     let left = self.and(step2, context.new_rvalue_from_long(typ, 0x0F0F0F0F));
 599                     let left = self.shl(left, context.new_rvalue_from_long(typ, 4));
 600                     let right = self.and(step2, context.new_rvalue_from_long(typ, 0xF0F0F0F0));
 601                     let right = self.lshr(right, context.new_rvalue_from_long(typ, 4));
 602                     let step3 = self.or(left, right);
 603
 604                     // Fourth step.
 605                     let left = self.and(step3, context.new_rvalue_from_long(typ, 0x00FF00FF));
 606                     let left = self.shl(left, context.new_rvalue_from_long(typ, 8));
 607                     let right = self.and(step3, context.new_rvalue_from_long(typ, 0xFF00FF00));
 608                     let right = self.lshr(right, context.new_rvalue_from_long(typ, 8));
 609                     let step4 = self.or(left, right);
 610
 611                     // Fifth step.
 612                     let left = self.and(step4, context.new_rvalue_from_long(typ, 0x0000FFFF));
 613                     let left = self.shl(left, context.new_rvalue_from_long(typ, 16));
 614                     let right = self.and(step4, context.new_rvalue_from_long(typ, 0xFFFF0000));
 615                     let right = self.lshr(right, context.new_rvalue_from_long(typ, 16));
 616                     let step5 = self.or(left, right);
 617
 618                     step5
 619                 },
 620                 64 => {
 621                     // First step.
 622                     let left = self.shl(value, context.new_rvalue_from_long(typ, 32));
 623                     let right = self.lshr(value, context.new_rvalue_from_long(typ, 32));
 624                     let step1 = self.or(left, right);
 625
 626                     // Second step.
 627                     let left = self.and(step1, context.new_rvalue_from_long(typ, 0x0001FFFF0001FFFF));
 628                     let left = self.shl(left, context.new_rvalue_from_long(typ, 15));
 629                     let right = self.and(step1, context.new_rvalue_from_long(typ, 0xFFFE0000FFFE0000u64 as i64)); // TODO(antoyo): transmute the number instead?
 630                     let right = self.lshr(right, context.new_rvalue_from_long(typ, 17));
 631                     let step2 = self.or(left, right);
 632
 633                     // Third step.
 634                     let left = self.lshr(step2, context.new_rvalue_from_long(typ, 10));
 635                     let left = self.xor(step2, left);
 636                     let temp = self.and(left, context.new_rvalue_from_long(typ, 0x003F801F003F801F));
 637
 638                     let left = self.shl(temp, context.new_rvalue_from_long(typ, 10));
 639                     let left = self.or(temp, left);
 640                     let step3 = self.xor(left, step2);
 641
 642                     // Fourth step.
 643                     let left = self.lshr(step3, context.new_rvalue_from_long(typ, 4));
 644                     let left = self.xor(step3, left);
 645                     let temp = self.and(left, context.new_rvalue_from_long(typ, 0x0E0384210E038421));
 646
 647                     let left = self.shl(temp, context.new_rvalue_from_long(typ, 4));
 648                     let left = self.or(temp, left);
 649                     let step4 = self.xor(left, step3);
 650
 651                     // Fifth step.
 652                     let left = self.lshr(step4, context.new_rvalue_from_long(typ, 2));
 653                     let left = self.xor(step4, left);
 654                     let temp = self.and(left, context.new_rvalue_from_long(typ, 0x2248884222488842));
 655
 656                     let left = self.shl(temp, context.new_rvalue_from_long(typ, 2));
 657                     let left = self.or(temp, left);
 658                     let step5 = self.xor(left, step4);
 659
 660                     step5
 661                 },
 662                 128 => {
 663                     // TODO(antoyo): find a more efficient implementation?
 664                     let sixty_four = self.gcc_int(typ, 64);
 665                     let right_shift = self.gcc_lshr(value, sixty_four);
 666                     let high = self.gcc_int_cast(right_shift, self.u64_type);
 667                     let low = self.gcc_int_cast(value, self.u64_type);
 668
 669                     let reversed_high = self.bit_reverse(64, high);
 670                     let reversed_low = self.bit_reverse(64, low);
 671
 672                     let new_low = self.gcc_int_cast(reversed_high, typ);
 673                     let new_high = self.shl(self.gcc_int_cast(reversed_low, typ), sixty_four);
 674
 675                     self.gcc_or(new_low, new_high)
 676                 },
 677                 _ => {
 678                     panic!("cannot bit reverse with width = {}", width);
 679                 },
 680             };
 681
 682         self.gcc_int_cast(result, result_type)
 683     }
 684
 685     fn count_leading_zeroes(&mut self, width: u64, arg: RValue<'gcc>) -> RValue<'gcc> {
 686         // TODO(antoyo): use width?
 687         let arg_type = arg.get_type();
 688         let count_leading_zeroes =
 689             // TODO(antoyo): write a new function Type::is_compatible_with(&Type) and use it here
 690             // instead of using is_uint().
 691             if arg_type.is_uint(&self.cx) {
 692                 "__builtin_clz"
 693             }
 694             else if arg_type.is_ulong(&self.cx) {
 695                 "__builtin_clzl"
 696             }
 697             else if arg_type.is_ulonglong(&self.cx) {
 698                 "__builtin_clzll"
 699             }
 700             else if width == 128 {
 701                 // Algorithm from: https://stackoverflow.com/a/28433850/389119
 702                 let array_type = self.context.new_array_type(None, arg_type, 3);
 703                 let result = self.current_func()
 704                     .new_local(None, array_type, "count_loading_zeroes_results");
 705
 706                 let sixty_four = self.const_uint(arg_type, 64);
 707                 let shift = self.lshr(arg, sixty_four);
 708                 let high = self.gcc_int_cast(shift, self.u64_type);
 709                 let low = self.gcc_int_cast(arg, self.u64_type);
 710
 711                 let zero = self.context.new_rvalue_zero(self.usize_type);
 712                 let one = self.context.new_rvalue_one(self.usize_type);
 713                 let two = self.context.new_rvalue_from_long(self.usize_type, 2);
 714
 715                 let clzll = self.context.get_builtin_function("__builtin_clzll");
 716
 717                 let first_elem = self.context.new_array_access(None, result, zero);
 718                 let first_value = self.gcc_int_cast(self.context.new_call(None, clzll, &[high]), arg_type);
 719                 self.llbb()
 720                     .add_assignment(None, first_elem, first_value);
 721
 722                 let second_elem = self.context.new_array_access(None, result, one);
 723                 let cast = self.gcc_int_cast(self.context.new_call(None, clzll, &[low]), arg_type);
 724                 let second_value = self.add(cast, sixty_four);
 725                 self.llbb()
 726                     .add_assignment(None, second_elem, second_value);
 727
 728                 let third_elem = self.context.new_array_access(None, result, two);
 729                 let third_value = self.const_uint(arg_type, 128);
 730                 self.llbb()
 731                     .add_assignment(None, third_elem, third_value);
 732
 733                 let not_high = self.context.new_unary_op(None, UnaryOp::LogicalNegate, self.u64_type, high);
 734                 let not_low = self.context.new_unary_op(None, UnaryOp::LogicalNegate, self.u64_type, low);
 735                 let not_low_and_not_high = not_low & not_high;
 736                 let index = not_high + not_low_and_not_high;
 737                 // NOTE: the following cast is necessary to avoid a GIMPLE verification failure in
 738                 // gcc.
 739                 // TODO(antoyo): do the correct verification in libgccjit to avoid an error at the
 740                 // compilation stage.
 741                 let index = self.context.new_cast(None, index, self.i32_type);
 742
 743                 let res = self.context.new_array_access(None, result, index);
 744
 745                 return self.gcc_int_cast(res.to_rvalue(), arg_type);
 746             }
 747             else {
 748                 let count_leading_zeroes = self.context.get_builtin_function("__builtin_clzll");
 749                 let arg = self.context.new_cast(None, arg, self.ulonglong_type);
 750                 let diff = self.ulonglong_type.get_size() as i64 - arg_type.get_size() as i64;
 751                 let diff = self.context.new_rvalue_from_long(self.int_type, diff * 8);
 752                 let res = self.context.new_call(None, count_leading_zeroes, &[arg]) - diff;
 753                 return self.context.new_cast(None, res, arg_type);
 754             };
 755         let count_leading_zeroes = self.context.get_builtin_function(count_leading_zeroes);
 756         let res = self.context.new_call(None, count_leading_zeroes, &[arg]);
 757         self.context.new_cast(None, res, arg_type)
 758     }
 759
 760     fn count_trailing_zeroes(&mut self, _width: u64, arg: RValue<'gcc>) -> RValue<'gcc> {
 761         let result_type = arg.get_type();
 762         let arg =
 763             if result_type.is_signed(self.cx) {
 764                 let new_type = result_type.to_unsigned(self.cx);
 765                 self.gcc_int_cast(arg, new_type)
 766             }
 767             else {
 768                 arg
 769             };
 770         let arg_type = arg.get_type();
 771         let (count_trailing_zeroes, expected_type) =
 772             // TODO(antoyo): write a new function Type::is_compatible_with(&Type) and use it here
 773             // instead of using is_uint().
 774             if arg_type.is_uchar(&self.cx) || arg_type.is_ushort(&self.cx) || arg_type.is_uint(&self.cx) {
 775                 // NOTE: we don't need to & 0xFF for uchar because the result is undefined on zero.
 776                 ("__builtin_ctz", self.cx.uint_type)
 777             }
 778             else if arg_type.is_ulong(&self.cx) {
 779                 ("__builtin_ctzl", self.cx.ulong_type)
 780             }
 781             else if arg_type.is_ulonglong(&self.cx) {
 782                 ("__builtin_ctzll", self.cx.ulonglong_type)
 783             }
 784             else if arg_type.is_u128(&self.cx) {
 785                 // Adapted from the algorithm to count leading zeroes from: https://stackoverflow.com/a/28433850/389119
 786                 let array_type = self.context.new_array_type(None, arg_type, 3);
 787                 let result = self.current_func()
 788                     .new_local(None, array_type, "count_loading_zeroes_results");
 789
 790                 let sixty_four = self.gcc_int(arg_type, 64);
 791                 let shift = self.gcc_lshr(arg, sixty_four);
 792                 let high = self.gcc_int_cast(shift, self.u64_type);
 793                 let low = self.gcc_int_cast(arg, self.u64_type);
 794
 795                 let zero = self.context.new_rvalue_zero(self.usize_type);
 796                 let one = self.context.new_rvalue_one(self.usize_type);
 797                 let two = self.context.new_rvalue_from_long(self.usize_type, 2);
 798
 799                 let ctzll = self.context.get_builtin_function("__builtin_ctzll");
 800
 801                 let first_elem = self.context.new_array_access(None, result, zero);
 802                 let first_value = self.gcc_int_cast(self.context.new_call(None, ctzll, &[low]), arg_type);
 803                 self.llbb()
 804                     .add_assignment(None, first_elem, first_value);
 805
 806                 let second_elem = self.context.new_array_access(None, result, one);
 807                 let second_value = self.gcc_add(self.gcc_int_cast(self.context.new_call(None, ctzll, &[high]), arg_type), sixty_four);
 808                 self.llbb()
 809                     .add_assignment(None, second_elem, second_value);
 810
 811                 let third_elem = self.context.new_array_access(None, result, two);
 812                 let third_value = self.gcc_int(arg_type, 128);
 813                 self.llbb()
 814                     .add_assignment(None, third_elem, third_value);
 815
 816                 let not_low = self.context.new_unary_op(None, UnaryOp::LogicalNegate, self.u64_type, low);
 817                 let not_high = self.context.new_unary_op(None, UnaryOp::LogicalNegate, self.u64_type, high);
 818                 let not_low_and_not_high = not_low & not_high;
 819                 let index = not_low + not_low_and_not_high;
 820                 // NOTE: the following cast is necessary to avoid a GIMPLE verification failure in
 821                 // gcc.
 822                 // TODO(antoyo): do the correct verification in libgccjit to avoid an error at the
 823                 // compilation stage.
 824                 let index = self.context.new_cast(None, index, self.i32_type);
 825
 826                 let res = self.context.new_array_access(None, result, index);
 827
 828                 return self.gcc_int_cast(res.to_rvalue(), result_type);
 829             }
 830             else {
 831                 let count_trailing_zeroes = self.context.get_builtin_function("__builtin_ctzll");
 832                 let arg_size = arg_type.get_size();
 833                 let casted_arg = self.context.new_cast(None, arg, self.ulonglong_type);
 834                 let byte_diff = self.ulonglong_type.get_size() as i64 - arg_size as i64;
 835                 let diff = self.context.new_rvalue_from_long(self.int_type, byte_diff * 8);
 836                 let mask = self.context.new_rvalue_from_long(arg_type, -1); // To get the value with all bits set.
 837                 let masked = mask & self.context.new_unary_op(None, UnaryOp::BitwiseNegate, arg_type, arg);
 838                 let cond = self.context.new_comparison(None, ComparisonOp::Equals, masked, mask);
 839                 let diff = diff * self.context.new_cast(None, cond, self.int_type);
 840                 let res = self.context.new_call(None, count_trailing_zeroes, &[casted_arg]) - diff;
 841                 return self.context.new_cast(None, res, result_type);
 842             };
 843         let count_trailing_zeroes = self.context.get_builtin_function(count_trailing_zeroes);
 844         let arg =
 845             if arg_type != expected_type {
 846                 self.context.new_cast(None, arg, expected_type)
 847             }
 848             else {
 849                 arg
 850             };
 851         let res = self.context.new_call(None, count_trailing_zeroes, &[arg]);
 852         self.context.new_cast(None, res, result_type)
 853     }
 854
 855     fn pop_count(&mut self, value: RValue<'gcc>) -> RValue<'gcc> {
 856         // TODO(antoyo): use the optimized version with fewer operations.
 857         let result_type = value.get_type();
 858         let value_type = result_type.to_unsigned(self.cx);
 859
 860         let value =
 861             if result_type.is_signed(self.cx) {
 862                 self.gcc_int_cast(value, value_type)
 863             }
 864             else {
 865                 value
 866             };
 867
 868         if value_type.is_u128(&self.cx) {
 869             // TODO(antoyo): implement in the normal algorithm below to have a more efficient
 870             // implementation (that does not require a call to __popcountdi2).
 871             let popcount = self.context.get_builtin_function("__builtin_popcountll");
 872             let sixty_four = self.gcc_int(value_type, 64);
 873             let right_shift = self.gcc_lshr(value, sixty_four);
 874             let high = self.gcc_int_cast(right_shift, self.cx.ulonglong_type);
 875             let high = self.context.new_call(None, popcount, &[high]);
 876             let low = self.gcc_int_cast(value, self.cx.ulonglong_type);
 877             let low = self.context.new_call(None, popcount, &[low]);
 878             let res = high + low;
 879             return self.gcc_int_cast(res, result_type);
 880         }
 881
 882         // First step.
 883         let mask = self.context.new_rvalue_from_long(value_type, 0x5555555555555555);
 884         let left = value & mask;
 885         let shifted = value >> self.context.new_rvalue_from_int(value_type, 1);
 886         let right = shifted & mask;
 887         let value = left + right;
 888
 889         // Second step.
 890         let mask = self.context.new_rvalue_from_long(value_type, 0x3333333333333333);
 891         let left = value & mask;
 892         let shifted = value >> self.context.new_rvalue_from_int(value_type, 2);
 893         let right = shifted & mask;
 894         let value = left + right;
 895
 896         // Third step.
 897         let mask = self.context.new_rvalue_from_long(value_type, 0x0F0F0F0F0F0F0F0F);
 898         let left = value & mask;
 899         let shifted = value >> self.context.new_rvalue_from_int(value_type, 4);
 900         let right = shifted & mask;
 901         let value = left + right;
 902
 903         if value_type.is_u8(&self.cx) {
 904             return self.context.new_cast(None, value, result_type);
 905         }
 906
 907         // Fourth step.
 908         let mask = self.context.new_rvalue_from_long(value_type, 0x00FF00FF00FF00FF);
 909         let left = value & mask;
 910         let shifted = value >> self.context.new_rvalue_from_int(value_type, 8);
 911         let right = shifted & mask;
 912         let value = left + right;
 913
 914         if value_type.is_u16(&self.cx) {
 915             return self.context.new_cast(None, value, result_type);
 916         }
 917
 918         // Fifth step.
 919         let mask = self.context.new_rvalue_from_long(value_type, 0x0000FFFF0000FFFF);
 920         let left = value & mask;
 921         let shifted = value >> self.context.new_rvalue_from_int(value_type, 16);
 922         let right = shifted & mask;
 923         let value = left + right;
 924
 925         if value_type.is_u32(&self.cx) {
 926             return self.context.new_cast(None, value, result_type);
 927         }
 928
 929         // Sixth step.
 930         let mask = self.context.new_rvalue_from_long(value_type, 0x00000000FFFFFFFF);
 931         let left = value & mask;
 932         let shifted = value >> self.context.new_rvalue_from_int(value_type, 32);
 933         let right = shifted & mask;
 934         let value = left + right;
 935
 936         self.context.new_cast(None, value, result_type)
 937     }
 938
 939     // Algorithm from: https://blog.regehr.org/archives/1063
 940     fn rotate_left(&mut self, value: RValue<'gcc>, shift: RValue<'gcc>, width: u64) -> RValue<'gcc> {
 941         let max = self.const_uint(shift.get_type(), width);
 942         let shift = self.urem(shift, max);
 943         let lhs = self.shl(value, shift);
 944         let result_neg = self.neg(shift);
 945         let result_and =
 946             self.and(
 947                 result_neg,
 948                 self.const_uint(shift.get_type(), width - 1),
 949             );
 950         let rhs = self.lshr(value, result_and);
 951         self.or(lhs, rhs)
 952     }
 953
 954     // Algorithm from: https://blog.regehr.org/archives/1063
 955     fn rotate_right(&mut self, value: RValue<'gcc>, shift: RValue<'gcc>, width: u64) -> RValue<'gcc> {
 956         let max = self.const_uint(shift.get_type(), width);
 957         let shift = self.urem(shift, max);
 958         let lhs = self.lshr(value, shift);
 959         let result_neg = self.neg(shift);
 960         let result_and =
 961             self.and(
 962                 result_neg,
 963                 self.const_uint(shift.get_type(), width - 1),
 964             );
 965         let rhs = self.shl(value, result_and);
 966         self.or(lhs, rhs)
 967     }
 968
 969     fn saturating_add(&mut self, lhs: RValue<'gcc>, rhs: RValue<'gcc>, signed: bool, width: u64) -> RValue<'gcc> {
 970         let result_type = lhs.get_type();
 971         if signed {
 972             // Based on algorithm from: https://stackoverflow.com/a/56531252/389119
 973             let func = self.current_func.borrow().expect("func");
 974             let res = func.new_local(None, result_type, "saturating_sum");
 975             let supports_native_type = self.is_native_int_type(result_type);
 976             let overflow =
 977                 if supports_native_type {
 978                     let func_name =
 979                         match width {
 980                             8 => "__builtin_add_overflow",
 981                             16 => "__builtin_add_overflow",
 982                             32 => "__builtin_sadd_overflow",
 983                             64 => "__builtin_saddll_overflow",
 984                             128 => "__builtin_add_overflow",
 985                             _ => unreachable!(),
 986                         };
 987                     let overflow_func = self.context.get_builtin_function(func_name);
 988                     self.overflow_call(overflow_func, &[lhs, rhs, res.get_address(None)], None)
 989                 }
 990                 else {
 991                     let func_name =
 992                         match width {
 993                             128 => "__rust_i128_addo",
 994                             _ => unreachable!(),
 995                         };
 996                     let param_a = self.context.new_parameter(None, result_type, "a");
 997                     let param_b = self.context.new_parameter(None, result_type, "b");
 998                     let result_field = self.context.new_field(None, result_type, "result");
 999                     let overflow_field = self.context.new_field(None, self.bool_type, "overflow");
1000                     let return_type = self.context.new_struct_type(None, "result_overflow", &[result_field, overflow_field]);
1001                     let func = self.context.new_function(None, FunctionType::Extern, return_type.as_type(), &[param_a, param_b], func_name, false);
1002                     let result = self.context.new_call(None, func, &[lhs, rhs]);
1003                     let overflow = result.access_field(None, overflow_field);
1004                     let int_result = result.access_field(None, result_field);
1005                     self.llbb().add_assignment(None, res, int_result);
1006                     overflow
1007                 };
1008
1009             let then_block = func.new_block("then");
1010             let after_block = func.new_block("after");
1011
1012             // Return `result_type`'s maximum or minimum value on overflow
1013             // NOTE: convert the type to unsigned to have an unsigned shift.
1014             let unsigned_type = result_type.to_unsigned(&self.cx);
1015             let shifted = self.gcc_lshr(self.gcc_int_cast(lhs, unsigned_type), self.gcc_int(unsigned_type, width as i64 - 1));
1016             let uint_max = self.gcc_not(self.gcc_int(unsigned_type, 0));
1017             let int_max = self.gcc_lshr(uint_max, self.gcc_int(unsigned_type, 1));
1018             then_block.add_assignment(None, res, self.gcc_int_cast(self.gcc_add(shifted, int_max), result_type));
1019             then_block.end_with_jump(None, after_block);
1020
1021             self.llbb().end_with_conditional(None, overflow, then_block, after_block);
1022
1023             // NOTE: since jumps were added in a place rustc does not
1024             // expect, the current block in the state need to be updated.
1025             self.switch_to_block(after_block);
1026
1027             res.to_rvalue()
1028         }
1029         else {
1030             // Algorithm from: http://locklessinc.com/articles/sat_arithmetic/
1031             let res = self.gcc_add(lhs, rhs);
1032             let cond = self.gcc_icmp(IntPredicate::IntULT, res, lhs);
1033             let value = self.gcc_neg(self.gcc_int_cast(cond, result_type));
1034             self.gcc_or(res, value)
1035         }
1036     }
1037
1038     // Algorithm from: https://locklessinc.com/articles/sat_arithmetic/
1039     fn saturating_sub(&mut self, lhs: RValue<'gcc>, rhs: RValue<'gcc>, signed: bool, width: u64) -> RValue<'gcc> {
1040         let result_type = lhs.get_type();
1041         if signed {
1042             // Based on algorithm from: https://stackoverflow.com/a/56531252/389119
1043             let func = self.current_func.borrow().expect("func");
1044             let res = func.new_local(None, result_type, "saturating_diff");
1045             let supports_native_type = self.is_native_int_type(result_type);
1046             let overflow =
1047                 if supports_native_type {
1048                     let func_name =
1049                         match width {
1050                             8 => "__builtin_sub_overflow",
1051                             16 => "__builtin_sub_overflow",
1052                             32 => "__builtin_ssub_overflow",
1053                             64 => "__builtin_ssubll_overflow",
1054                             128 => "__builtin_sub_overflow",
1055                             _ => unreachable!(),
1056                         };
1057                     let overflow_func = self.context.get_builtin_function(func_name);
1058                     self.overflow_call(overflow_func, &[lhs, rhs, res.get_address(None)], None)
1059                 }
1060                 else {
1061                     let func_name =
1062                         match width {
1063                             128 => "__rust_i128_subo",
1064                             _ => unreachable!(),
1065                         };
1066                     let param_a = self.context.new_parameter(None, result_type, "a");
1067                     let param_b = self.context.new_parameter(None, result_type, "b");
1068                     let result_field = self.context.new_field(None, result_type, "result");
1069                     let overflow_field = self.context.new_field(None, self.bool_type, "overflow");
1070                     let return_type = self.context.new_struct_type(None, "result_overflow", &[result_field, overflow_field]);
1071                     let func = self.context.new_function(None, FunctionType::Extern, return_type.as_type(), &[param_a, param_b], func_name, false);
1072                     let result = self.context.new_call(None, func, &[lhs, rhs]);
1073                     let overflow = result.access_field(None, overflow_field);
1074                     let int_result = result.access_field(None, result_field);
1075                     self.llbb().add_assignment(None, res, int_result);
1076                     overflow
1077                 };
1078
1079             let then_block = func.new_block("then");
1080             let after_block = func.new_block("after");
1081
1082             // Return `result_type`'s maximum or minimum value on overflow
1083             // NOTE: convert the type to unsigned to have an unsigned shift.
1084             let unsigned_type = result_type.to_unsigned(&self.cx);
1085             let shifted = self.gcc_lshr(self.gcc_int_cast(lhs, unsigned_type), self.gcc_int(unsigned_type, width as i64 - 1));
1086             let uint_max = self.gcc_not(self.gcc_int(unsigned_type, 0));
1087             let int_max = self.gcc_lshr(uint_max, self.gcc_int(unsigned_type, 1));
1088             then_block.add_assignment(None, res, self.gcc_int_cast(self.gcc_add(shifted, int_max), result_type));
1089             then_block.end_with_jump(None, after_block);
1090
1091             self.llbb().end_with_conditional(None, overflow, then_block, after_block);
1092
1093             // NOTE: since jumps were added in a place rustc does not
1094             // expect, the current block in the state need to be updated.
1095             self.switch_to_block(after_block);
1096
1097             res.to_rvalue()
1098         }
1099         else {
1100             let res = self.gcc_sub(lhs, rhs);
1101             let comparison = self.gcc_icmp(IntPredicate::IntULE, res, lhs);
1102             let value = self.gcc_neg(self.gcc_int_cast(comparison, result_type));
1103             self.gcc_and(res, value)
1104         }
1105     }
1106 }
1107
1108 fn try_intrinsic<'gcc, 'tcx>(bx: &mut Builder<'_, 'gcc, 'tcx>, try_func: RValue<'gcc>, data: RValue<'gcc>, _catch_func: RValue<'gcc>, dest: RValue<'gcc>) {
1109     // NOTE: the `|| true` here is to use the panic=abort strategy with panic=unwind too
1110     if bx.sess().panic_strategy() == PanicStrategy::Abort || true {
1111         // TODO(bjorn3): Properly implement unwinding and remove the `|| true` once this is done.
1112         bx.call(bx.type_void(), try_func, &[data], None);
1113         // Return 0 unconditionally from the intrinsic call;
1114         // we can never unwind.
1115         let ret_align = bx.tcx.data_layout.i32_align.abi;
1116         bx.store(bx.const_i32(0), dest, ret_align);
1117     }
1118     else if wants_msvc_seh(bx.sess()) {
1119         unimplemented!();
1120     }
1121     else {
1122         unimplemented!();
1123     }
1124 }