rttype.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package rttype allows the compiler to share type information with
     6  // the runtime. The shared type information is stored in
     7  // internal/abi. This package translates those types from the host
     8  // machine on which the compiler runs to the target machine on which
     9  // the compiled program will run. In particular, this package handles
    10  // layout differences between e.g. a 64 bit compiler and 32 bit
    11  // target.
    12  package rttype
    13  
    14  import (
    15  	"cmd/compile/internal/base"
    16  	"cmd/compile/internal/objw"
    17  	"cmd/compile/internal/types"
    18  	"cmd/internal/obj"
    19  	"internal/abi"
    20  	"reflect"
    21  )
    22  
    23  // The type structures shared with the runtime.
    24  var Type *types.Type
    25  
    26  var ArrayType *types.Type
    27  var ChanType *types.Type
    28  var FuncType *types.Type
    29  var InterfaceType *types.Type
    30  var MapType *types.Type
    31  var PtrType *types.Type
    32  var SliceType *types.Type
    33  var StructType *types.Type
    34  
    35  // Types that are parts of the types above.
    36  var IMethod *types.Type
    37  var Method *types.Type
    38  var StructField *types.Type
    39  var UncommonType *types.Type
    40  
    41  // Type switches and asserts
    42  var InterfaceSwitch *types.Type
    43  var TypeAssert *types.Type
    44  
    45  // Interface tables (itabs)
    46  var ITab *types.Type
    47  
    48  func Init() {
    49  	// Note: this has to be called explicitly instead of being
    50  	// an init function so it runs after the types package has
    51  	// been properly initialized.
    52  	Type = FromReflect(reflect.TypeOf(abi.Type{}))
    53  	ArrayType = FromReflect(reflect.TypeOf(abi.ArrayType{}))
    54  	ChanType = FromReflect(reflect.TypeOf(abi.ChanType{}))
    55  	FuncType = FromReflect(reflect.TypeOf(abi.FuncType{}))
    56  	InterfaceType = FromReflect(reflect.TypeOf(abi.InterfaceType{}))
    57  	MapType = FromReflect(reflect.TypeOf(abi.MapType{}))
    58  	PtrType = FromReflect(reflect.TypeOf(abi.PtrType{}))
    59  	SliceType = FromReflect(reflect.TypeOf(abi.SliceType{}))
    60  	StructType = FromReflect(reflect.TypeOf(abi.StructType{}))
    61  
    62  	IMethod = FromReflect(reflect.TypeOf(abi.Imethod{}))
    63  	Method = FromReflect(reflect.TypeOf(abi.Method{}))
    64  	StructField = FromReflect(reflect.TypeOf(abi.StructField{}))
    65  	UncommonType = FromReflect(reflect.TypeOf(abi.UncommonType{}))
    66  
    67  	InterfaceSwitch = FromReflect(reflect.TypeOf(abi.InterfaceSwitch{}))
    68  	TypeAssert = FromReflect(reflect.TypeOf(abi.TypeAssert{}))
    69  
    70  	ITab = FromReflect(reflect.TypeOf(abi.ITab{}))
    71  
    72  	// Make sure abi functions are correct. These functions are used
    73  	// by the linker which doesn't have the ability to do type layout,
    74  	// so we check the functions it uses here.
    75  	ptrSize := types.PtrSize
    76  	if got, want := int64(abi.CommonSize(ptrSize)), Type.Size(); got != want {
    77  		base.Fatalf("abi.CommonSize() == %d, want %d", got, want)
    78  	}
    79  	if got, want := int64(abi.StructFieldSize(ptrSize)), StructField.Size(); got != want {
    80  		base.Fatalf("abi.StructFieldSize() == %d, want %d", got, want)
    81  	}
    82  	if got, want := int64(abi.UncommonSize()), UncommonType.Size(); got != want {
    83  		base.Fatalf("abi.UncommonSize() == %d, want %d", got, want)
    84  	}
    85  	if got, want := int64(abi.TFlagOff(ptrSize)), Type.OffsetOf("TFlag"); got != want {
    86  		base.Fatalf("abi.TFlagOff() == %d, want %d", got, want)
    87  	}
    88  	if got, want := int64(abi.ITabTypeOff(ptrSize)), ITab.OffsetOf("Type"); got != want {
    89  		base.Fatalf("abi.ITabTypeOff() == %d, want %d", got, want)
    90  	}
    91  }
    92  
    93  // FromReflect translates from a host type to the equivalent target type.
    94  func FromReflect(rt reflect.Type) *types.Type {
    95  	t := reflectToType(rt)
    96  	types.CalcSize(t)
    97  	return t
    98  }
    99  
   100  // reflectToType converts from a reflect.Type (which is a compiler
   101  // host type) to a *types.Type, which is a target type.  The result
   102  // must be CalcSize'd before using.
   103  func reflectToType(rt reflect.Type) *types.Type {
   104  	switch rt.Kind() {
   105  	case reflect.Bool:
   106  		return types.Types[types.TBOOL]
   107  	case reflect.Int:
   108  		return types.Types[types.TINT]
   109  	case reflect.Int8:
   110  		return types.Types[types.TINT8]
   111  	case reflect.Int16:
   112  		return types.Types[types.TINT16]
   113  	case reflect.Int32:
   114  		return types.Types[types.TINT32]
   115  	case reflect.Uint8:
   116  		return types.Types[types.TUINT8]
   117  	case reflect.Uint16:
   118  		return types.Types[types.TUINT16]
   119  	case reflect.Uint32:
   120  		return types.Types[types.TUINT32]
   121  	case reflect.Float32:
   122  		return types.Types[types.TFLOAT32]
   123  	case reflect.Float64:
   124  		return types.Types[types.TFLOAT64]
   125  	case reflect.Uintptr:
   126  		return types.Types[types.TUINTPTR]
   127  	case reflect.Ptr:
   128  		return types.NewPtr(reflectToType(rt.Elem()))
   129  	case reflect.Func, reflect.UnsafePointer:
   130  		// TODO: there's no mechanism to distinguish different pointer types,
   131  		// so we treat them all as unsafe.Pointer.
   132  		return types.Types[types.TUNSAFEPTR]
   133  	case reflect.Slice:
   134  		return types.NewSlice(reflectToType(rt.Elem()))
   135  	case reflect.Array:
   136  		return types.NewArray(reflectToType(rt.Elem()), int64(rt.Len()))
   137  	case reflect.Struct:
   138  		fields := make([]*types.Field, rt.NumField())
   139  		for i := 0; i < rt.NumField(); i++ {
   140  			f := rt.Field(i)
   141  			ft := reflectToType(f.Type)
   142  			fields[i] = &types.Field{Sym: &types.Sym{Name: f.Name}, Type: ft}
   143  		}
   144  		return types.NewStruct(fields)
   145  	case reflect.Chan:
   146  		return types.NewChan(reflectToType(rt.Elem()), types.ChanDir(rt.ChanDir()))
   147  	case reflect.String:
   148  		return types.Types[types.TSTRING]
   149  	case reflect.Complex128:
   150  		return types.Types[types.TCOMPLEX128]
   151  	default:
   152  		base.Fatalf("unhandled kind %s", rt.Kind())
   153  		return nil
   154  	}
   155  }
   156  
   157  // A Cursor represents a typed location inside a static variable where we
   158  // are going to write.
   159  type Cursor struct {
   160  	lsym   *obj.LSym
   161  	offset int64
   162  	typ    *types.Type
   163  }
   164  
   165  // NewCursor returns a cursor starting at lsym+off and having type t.
   166  func NewCursor(lsym *obj.LSym, off int64, t *types.Type) Cursor {
   167  	return Cursor{lsym: lsym, offset: off, typ: t}
   168  }
   169  
   170  // WritePtr writes a pointer "target" to the component at the location specified by c.
   171  func (c Cursor) WritePtr(target *obj.LSym) {
   172  	if c.typ.Kind() != types.TUNSAFEPTR && c.typ.Kind() != types.TPTR {
   173  		base.Fatalf("can't write ptr, it has kind %s", c.typ.Kind())
   174  	}
   175  	if target == nil {
   176  		objw.Uintptr(c.lsym, int(c.offset), 0)
   177  	} else {
   178  		objw.SymPtr(c.lsym, int(c.offset), target, 0)
   179  	}
   180  }
   181  func (c Cursor) WritePtrWeak(target *obj.LSym) {
   182  	if c.typ.Kind() != types.TUINTPTR {
   183  		base.Fatalf("can't write ptr, it has kind %s", c.typ.Kind())
   184  	}
   185  	objw.SymPtrWeak(c.lsym, int(c.offset), target, 0)
   186  }
   187  func (c Cursor) WriteUintptr(val uint64) {
   188  	if c.typ.Kind() != types.TUINTPTR {
   189  		base.Fatalf("can't write uintptr, it has kind %s", c.typ.Kind())
   190  	}
   191  	objw.Uintptr(c.lsym, int(c.offset), val)
   192  }
   193  func (c Cursor) WriteUint32(val uint32) {
   194  	if c.typ.Kind() != types.TUINT32 {
   195  		base.Fatalf("can't write uint32, it has kind %s", c.typ.Kind())
   196  	}
   197  	objw.Uint32(c.lsym, int(c.offset), val)
   198  }
   199  func (c Cursor) WriteUint16(val uint16) {
   200  	if c.typ.Kind() != types.TUINT16 {
   201  		base.Fatalf("can't write uint16, it has kind %s", c.typ.Kind())
   202  	}
   203  	objw.Uint16(c.lsym, int(c.offset), val)
   204  }
   205  func (c Cursor) WriteUint8(val uint8) {
   206  	if c.typ.Kind() != types.TUINT8 {
   207  		base.Fatalf("can't write uint8, it has kind %s", c.typ.Kind())
   208  	}
   209  	objw.Uint8(c.lsym, int(c.offset), val)
   210  }
   211  func (c Cursor) WriteInt(val int64) {
   212  	if c.typ.Kind() != types.TINT {
   213  		base.Fatalf("can't write int, it has kind %s", c.typ.Kind())
   214  	}
   215  	objw.Uintptr(c.lsym, int(c.offset), uint64(val))
   216  }
   217  func (c Cursor) WriteInt32(val int32) {
   218  	if c.typ.Kind() != types.TINT32 {
   219  		base.Fatalf("can't write int32, it has kind %s", c.typ.Kind())
   220  	}
   221  	objw.Uint32(c.lsym, int(c.offset), uint32(val))
   222  }
   223  func (c Cursor) WriteBool(val bool) {
   224  	if c.typ.Kind() != types.TBOOL {
   225  		base.Fatalf("can't write bool, it has kind %s", c.typ.Kind())
   226  	}
   227  	objw.Bool(c.lsym, int(c.offset), val)
   228  }
   229  
   230  // WriteSymPtrOff writes a "pointer" to the given symbol. The symbol
   231  // is encoded as a uint32 offset from the start of the section.
   232  func (c Cursor) WriteSymPtrOff(target *obj.LSym, weak bool) {
   233  	if c.typ.Kind() != types.TINT32 && c.typ.Kind() != types.TUINT32 {
   234  		base.Fatalf("can't write SymPtr, it has kind %s", c.typ.Kind())
   235  	}
   236  	if target == nil {
   237  		objw.Uint32(c.lsym, int(c.offset), 0)
   238  	} else if weak {
   239  		objw.SymPtrWeakOff(c.lsym, int(c.offset), target)
   240  	} else {
   241  		objw.SymPtrOff(c.lsym, int(c.offset), target)
   242  	}
   243  }
   244  
   245  // WriteSlice writes a slice header to c. The pointer is target+off, the len and cap fields are given.
   246  func (c Cursor) WriteSlice(target *obj.LSym, off, len, cap int64) {
   247  	if c.typ.Kind() != types.TSLICE {
   248  		base.Fatalf("can't write slice, it has kind %s", c.typ.Kind())
   249  	}
   250  	objw.SymPtr(c.lsym, int(c.offset), target, int(off))
   251  	objw.Uintptr(c.lsym, int(c.offset)+types.PtrSize, uint64(len))
   252  	objw.Uintptr(c.lsym, int(c.offset)+2*types.PtrSize, uint64(cap))
   253  	// TODO: ability to switch len&cap. Maybe not needed here, as every caller
   254  	// passes the same thing for both?
   255  	if len != cap {
   256  		base.Fatalf("len != cap (%d != %d)", len, cap)
   257  	}
   258  }
   259  
   260  // Reloc adds a relocation from the current cursor position.
   261  // Reloc fills in Off and Siz fields. Caller should fill in the rest (Type, others).
   262  func (c Cursor) Reloc(rel obj.Reloc) {
   263  	rel.Off = int32(c.offset)
   264  	rel.Siz = uint8(c.typ.Size())
   265  	c.lsym.AddRel(base.Ctxt, rel)
   266  }
   267  
   268  // Field selects the field with the given name from the struct pointed to by c.
   269  func (c Cursor) Field(name string) Cursor {
   270  	if c.typ.Kind() != types.TSTRUCT {
   271  		base.Fatalf("can't call Field on non-struct %v", c.typ)
   272  	}
   273  	for _, f := range c.typ.Fields() {
   274  		if f.Sym.Name == name {
   275  			return Cursor{lsym: c.lsym, offset: c.offset + f.Offset, typ: f.Type}
   276  		}
   277  	}
   278  	base.Fatalf("couldn't find field %s in %v", name, c.typ)
   279  	return Cursor{}
   280  }
   281  
   282  func (c Cursor) Elem(i int64) Cursor {
   283  	if c.typ.Kind() != types.TARRAY {
   284  		base.Fatalf("can't call Elem on non-array %v", c.typ)
   285  	}
   286  	if i < 0 || i >= c.typ.NumElem() {
   287  		base.Fatalf("element access out of bounds [%d] in [0:%d]", i, c.typ.NumElem())
   288  	}
   289  	elem := c.typ.Elem()
   290  	return Cursor{lsym: c.lsym, offset: c.offset + i*elem.Size(), typ: elem}
   291  }
   292  
   293  type ArrayCursor struct {
   294  	c Cursor // cursor pointing at first element
   295  	n int    // number of elements
   296  }
   297  
   298  // NewArrayCursor returns a cursor starting at lsym+off and having n copies of type t.
   299  func NewArrayCursor(lsym *obj.LSym, off int64, t *types.Type, n int) ArrayCursor {
   300  	return ArrayCursor{
   301  		c: NewCursor(lsym, off, t),
   302  		n: n,
   303  	}
   304  }
   305  
   306  // Elem selects element i of the array pointed to by c.
   307  func (a ArrayCursor) Elem(i int) Cursor {
   308  	if i < 0 || i >= a.n {
   309  		base.Fatalf("element index %d out of range [0:%d]", i, a.n)
   310  	}
   311  	return Cursor{lsym: a.c.lsym, offset: a.c.offset + int64(i)*a.c.typ.Size(), typ: a.c.typ}
   312  }
   313  
   314  // ModifyArray converts a cursor pointing at a type [k]T to a cursor pointing
   315  // at a type [n]T.
   316  // Also returns the size delta, aka (n-k)*sizeof(T).
   317  func (c Cursor) ModifyArray(n int) (ArrayCursor, int64) {
   318  	if c.typ.Kind() != types.TARRAY {
   319  		base.Fatalf("can't call ModifyArray on non-array %v", c.typ)
   320  	}
   321  	k := c.typ.NumElem()
   322  	return ArrayCursor{c: Cursor{lsym: c.lsym, offset: c.offset, typ: c.typ.Elem()}, n: n}, (int64(n) - k) * c.typ.Elem().Size()
   323  }
   324
View as plain text