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.Int32:
   110  		return types.Types[types.TINT32]
   111  	case reflect.Uint8:
   112  		return types.Types[types.TUINT8]
   113  	case reflect.Uint16:
   114  		return types.Types[types.TUINT16]
   115  	case reflect.Uint32:
   116  		return types.Types[types.TUINT32]
   117  	case reflect.Uintptr:
   118  		return types.Types[types.TUINTPTR]
   119  	case reflect.Ptr, reflect.Func, reflect.UnsafePointer:
   120  		// TODO: there's no mechanism to distinguish different pointer types,
   121  		// so we treat them all as unsafe.Pointer.
   122  		return types.Types[types.TUNSAFEPTR]
   123  	case reflect.Slice:
   124  		return types.NewSlice(reflectToType(rt.Elem()))
   125  	case reflect.Array:
   126  		return types.NewArray(reflectToType(rt.Elem()), int64(rt.Len()))
   127  	case reflect.Struct:
   128  		fields := make([]*types.Field, rt.NumField())
   129  		for i := 0; i < rt.NumField(); i++ {
   130  			f := rt.Field(i)
   131  			ft := reflectToType(f.Type)
   132  			fields[i] = &types.Field{Sym: &types.Sym{Name: f.Name}, Type: ft}
   133  		}
   134  		return types.NewStruct(fields)
   135  	default:
   136  		base.Fatalf("unhandled kind %s", rt.Kind())
   137  		return nil
   138  	}
   139  }
   140  
   141  // A Cursor represents a typed location inside a static variable where we
   142  // are going to write.
   143  type Cursor struct {
   144  	lsym   *obj.LSym
   145  	offset int64
   146  	typ    *types.Type
   147  }
   148  
   149  // NewCursor returns a cursor starting at lsym+off and having type t.
   150  func NewCursor(lsym *obj.LSym, off int64, t *types.Type) Cursor {
   151  	return Cursor{lsym: lsym, offset: off, typ: t}
   152  }
   153  
   154  // WritePtr writes a pointer "target" to the component at the location specified by c.
   155  func (c Cursor) WritePtr(target *obj.LSym) {
   156  	if c.typ.Kind() != types.TUNSAFEPTR {
   157  		base.Fatalf("can't write ptr, it has kind %s", c.typ.Kind())
   158  	}
   159  	if target == nil {
   160  		objw.Uintptr(c.lsym, int(c.offset), 0)
   161  	} else {
   162  		objw.SymPtr(c.lsym, int(c.offset), target, 0)
   163  	}
   164  }
   165  func (c Cursor) WritePtrWeak(target *obj.LSym) {
   166  	if c.typ.Kind() != types.TUINTPTR {
   167  		base.Fatalf("can't write ptr, it has kind %s", c.typ.Kind())
   168  	}
   169  	objw.SymPtrWeak(c.lsym, int(c.offset), target, 0)
   170  }
   171  func (c Cursor) WriteUintptr(val uint64) {
   172  	if c.typ.Kind() != types.TUINTPTR {
   173  		base.Fatalf("can't write uintptr, it has kind %s", c.typ.Kind())
   174  	}
   175  	objw.Uintptr(c.lsym, int(c.offset), val)
   176  }
   177  func (c Cursor) WriteUint32(val uint32) {
   178  	if c.typ.Kind() != types.TUINT32 {
   179  		base.Fatalf("can't write uint32, it has kind %s", c.typ.Kind())
   180  	}
   181  	objw.Uint32(c.lsym, int(c.offset), val)
   182  }
   183  func (c Cursor) WriteUint16(val uint16) {
   184  	if c.typ.Kind() != types.TUINT16 {
   185  		base.Fatalf("can't write uint16, it has kind %s", c.typ.Kind())
   186  	}
   187  	objw.Uint16(c.lsym, int(c.offset), val)
   188  }
   189  func (c Cursor) WriteUint8(val uint8) {
   190  	if c.typ.Kind() != types.TUINT8 {
   191  		base.Fatalf("can't write uint8, it has kind %s", c.typ.Kind())
   192  	}
   193  	objw.Uint8(c.lsym, int(c.offset), val)
   194  }
   195  func (c Cursor) WriteInt(val int64) {
   196  	if c.typ.Kind() != types.TINT {
   197  		base.Fatalf("can't write int, it has kind %s", c.typ.Kind())
   198  	}
   199  	objw.Uintptr(c.lsym, int(c.offset), uint64(val))
   200  }
   201  func (c Cursor) WriteInt32(val int32) {
   202  	if c.typ.Kind() != types.TINT32 {
   203  		base.Fatalf("can't write int32, it has kind %s", c.typ.Kind())
   204  	}
   205  	objw.Uint32(c.lsym, int(c.offset), uint32(val))
   206  }
   207  func (c Cursor) WriteBool(val bool) {
   208  	if c.typ.Kind() != types.TBOOL {
   209  		base.Fatalf("can't write bool, it has kind %s", c.typ.Kind())
   210  	}
   211  	objw.Bool(c.lsym, int(c.offset), val)
   212  }
   213  
   214  // WriteSymPtrOff writes a "pointer" to the given symbol. The symbol
   215  // is encoded as a uint32 offset from the start of the section.
   216  func (c Cursor) WriteSymPtrOff(target *obj.LSym, weak bool) {
   217  	if c.typ.Kind() != types.TINT32 && c.typ.Kind() != types.TUINT32 {
   218  		base.Fatalf("can't write SymPtr, it has kind %s", c.typ.Kind())
   219  	}
   220  	if target == nil {
   221  		objw.Uint32(c.lsym, int(c.offset), 0)
   222  	} else if weak {
   223  		objw.SymPtrWeakOff(c.lsym, int(c.offset), target)
   224  	} else {
   225  		objw.SymPtrOff(c.lsym, int(c.offset), target)
   226  	}
   227  }
   228  
   229  // WriteSlice writes a slice header to c. The pointer is target+off, the len and cap fields are given.
   230  func (c Cursor) WriteSlice(target *obj.LSym, off, len, cap int64) {
   231  	if c.typ.Kind() != types.TSLICE {
   232  		base.Fatalf("can't write slice, it has kind %s", c.typ.Kind())
   233  	}
   234  	objw.SymPtr(c.lsym, int(c.offset), target, int(off))
   235  	objw.Uintptr(c.lsym, int(c.offset)+types.PtrSize, uint64(len))
   236  	objw.Uintptr(c.lsym, int(c.offset)+2*types.PtrSize, uint64(cap))
   237  	// TODO: ability to switch len&cap. Maybe not needed here, as every caller
   238  	// passes the same thing for both?
   239  	if len != cap {
   240  		base.Fatalf("len != cap (%d != %d)", len, cap)
   241  	}
   242  }
   243  
   244  // Reloc adds a relocation from the current cursor position.
   245  // Reloc fills in Off and Siz fields. Caller should fill in the rest (Type, others).
   246  func (c Cursor) Reloc() *obj.Reloc {
   247  	r := obj.Addrel(c.lsym)
   248  	r.Off = int32(c.offset)
   249  	r.Siz = uint8(c.typ.Size())
   250  	return r
   251  }
   252  
   253  // Field selects the field with the given name from the struct pointed to by c.
   254  func (c Cursor) Field(name string) Cursor {
   255  	if c.typ.Kind() != types.TSTRUCT {
   256  		base.Fatalf("can't call Field on non-struct %v", c.typ)
   257  	}
   258  	for _, f := range c.typ.Fields() {
   259  		if f.Sym.Name == name {
   260  			return Cursor{lsym: c.lsym, offset: c.offset + f.Offset, typ: f.Type}
   261  		}
   262  	}
   263  	base.Fatalf("couldn't find field %s in %v", name, c.typ)
   264  	return Cursor{}
   265  }
   266  
   267  func (c Cursor) Elem(i int64) Cursor {
   268  	if c.typ.Kind() != types.TARRAY {
   269  		base.Fatalf("can't call Elem on non-array %v", c.typ)
   270  	}
   271  	if i < 0 || i >= c.typ.NumElem() {
   272  		base.Fatalf("element access out of bounds [%d] in [0:%d]", i, c.typ.NumElem())
   273  	}
   274  	elem := c.typ.Elem()
   275  	return Cursor{lsym: c.lsym, offset: c.offset + i*elem.Size(), typ: elem}
   276  }
   277  
   278  type ArrayCursor struct {
   279  	c Cursor // cursor pointing at first element
   280  	n int    // number of elements
   281  }
   282  
   283  // NewArrayCursor returns a cursor starting at lsym+off and having n copies of type t.
   284  func NewArrayCursor(lsym *obj.LSym, off int64, t *types.Type, n int) ArrayCursor {
   285  	return ArrayCursor{
   286  		c: NewCursor(lsym, off, t),
   287  		n: n,
   288  	}
   289  }
   290  
   291  // Elem selects element i of the array pointed to by c.
   292  func (a ArrayCursor) Elem(i int) Cursor {
   293  	if i < 0 || i >= a.n {
   294  		base.Fatalf("element index %d out of range [0:%d]", i, a.n)
   295  	}
   296  	return Cursor{lsym: a.c.lsym, offset: a.c.offset + int64(i)*a.c.typ.Size(), typ: a.c.typ}
   297  }
   298  
   299  // ModifyArray converts a cursor pointing at a type [k]T to a cursor pointing
   300  // at a type [n]T.
   301  // Also returns the size delta, aka (n-k)*sizeof(T).
   302  func (c Cursor) ModifyArray(n int) (ArrayCursor, int64) {
   303  	if c.typ.Kind() != types.TARRAY {
   304  		base.Fatalf("can't call ModifyArray on non-array %v", c.typ)
   305  	}
   306  	k := c.typ.NumElem()
   307  	return ArrayCursor{c: Cursor{lsym: c.lsym, offset: c.offset, typ: c.typ.Elem()}, n: n}, (int64(n) - k) * c.typ.Elem().Size()
   308  }
   309
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