Auto merge of #30586 - nagisa:mir-cast, r=arielb1

I think that should pretty much conclude all of #29576.

Author: bors

src/librustc_trans/trans/mir/rvalue.rs

@@ -10,6 +10,7 @@
 
 use llvm::ValueRef;
 use rustc::middle::ty::{self, Ty};
+use middle::ty::cast::{CastTy, IntTy};
 use rustc::mir::repr as mir;
 
 use trans::asm;
@@ -199,7 +200,89 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
                             }
                         }
                     }
-                    mir::CastKind::Misc => unimplemented!()
+                    mir::CastKind::Misc if common::type_is_immediate(bcx.ccx(), operand.ty) => {
+                        debug_assert!(common::type_is_immediate(bcx.ccx(), cast_ty));
+                        let r_t_in = CastTy::from_ty(operand.ty).expect("bad input type for cast");
+                        let r_t_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
+                        let ll_t_in = type_of::arg_type_of(bcx.ccx(), operand.ty);
+                        let ll_t_out = type_of::arg_type_of(bcx.ccx(), cast_ty);
+                        let (llval, ll_t_in, signed) = if let CastTy::Int(IntTy::CEnum) = r_t_in {
+                            let repr = adt::represent_type(bcx.ccx(), operand.ty);
+                            let llval = operand.immediate();
+                            let discr = adt::trans_get_discr(bcx, &*repr, llval, None);
+                            (discr, common::val_ty(discr), adt::is_discr_signed(&*repr))
+                        } else {
+                            (operand.immediate(), ll_t_in, operand.ty.is_signed())
+                        };
+
+                        let newval = match (r_t_in, r_t_out) {
+                            (CastTy::Int(_), CastTy::Int(_)) => {
+                                let srcsz = ll_t_in.int_width();
+                                let dstsz = ll_t_out.int_width();
+                                if srcsz == dstsz {
+                                    build::BitCast(bcx, llval, ll_t_out)
+                                } else if srcsz > dstsz {
+                                    build::Trunc(bcx, llval, ll_t_out)
+                                } else if signed {
+                                    build::SExt(bcx, llval, ll_t_out)
+                                } else {
+                                    build::ZExt(bcx, llval, ll_t_out)
+                                }
+                            }
+                            (CastTy::Float, CastTy::Float) => {
+                                let srcsz = ll_t_in.float_width();
+                                let dstsz = ll_t_out.float_width();
+                                if dstsz > srcsz {
+                                    build::FPExt(bcx, llval, ll_t_out)
+                                } else if srcsz > dstsz {
+                                    build::FPTrunc(bcx, llval, ll_t_out)
+                                } else {
+                                    llval
+                                }
+                            }
+                            (CastTy::Ptr(_), CastTy::Ptr(_)) |
+                            (CastTy::FnPtr, CastTy::Ptr(_)) |
+                            (CastTy::RPtr(_), CastTy::Ptr(_)) =>
+                                build::PointerCast(bcx, llval, ll_t_out),
+                            (CastTy::Ptr(_), CastTy::Int(_)) |
+                            (CastTy::FnPtr, CastTy::Int(_)) =>
+                                build::PtrToInt(bcx, llval, ll_t_out),
+                            (CastTy::Int(_), CastTy::Ptr(_)) =>
+                                build::IntToPtr(bcx, llval, ll_t_out),
+                            (CastTy::Int(_), CastTy::Float) if signed =>
+                                build::SIToFP(bcx, llval, ll_t_out),
+                            (CastTy::Int(_), CastTy::Float) =>
+                                build::UIToFP(bcx, llval, ll_t_out),
+                            (CastTy::Float, CastTy::Int(IntTy::I)) =>
+                                build::FPToSI(bcx, llval, ll_t_out),
+                            (CastTy::Float, CastTy::Int(_)) =>
+                                build::FPToUI(bcx, llval, ll_t_out),
+                            _ => bcx.ccx().sess().bug(
+                                &format!("unsupported cast: {:?} to {:?}", operand.ty, cast_ty)
+                            )
+                        };
+                        OperandValue::Immediate(newval)
+                    }
+                    mir::CastKind::Misc => { // Casts from a fat-ptr.
+                        let ll_cast_ty = type_of::arg_type_of(bcx.ccx(), cast_ty);
+                        let ll_from_ty = type_of::arg_type_of(bcx.ccx(), operand.ty);
+                        if let OperandValue::FatPtr(data_ptr, meta_ptr) = operand.val {
+                            if common::type_is_fat_ptr(bcx.tcx(), cast_ty) {
+                                let ll_cft = ll_cast_ty.field_types();
+                                let ll_fft = ll_from_ty.field_types();
+                                let data_cast = build::PointerCast(bcx, data_ptr, ll_cft[0]);
+                                assert_eq!(ll_cft[1].kind(), ll_fft[1].kind());
+                                OperandValue::FatPtr(data_cast, meta_ptr)
+                            } else { // cast to thin-ptr
+                                // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
+                                // pointer-cast of that pointer to desired pointer type.
+                                let llval = build::PointerCast(bcx, data_ptr, ll_cast_ty);
+                                OperandValue::Immediate(llval)
+                            }
+                        } else {
+                            panic!("Unexpected non-FatPtr operand")
+                        }
+                    }
                 };
                 (bcx, OperandRef {
                     val: val,