alg.go

     1  // Copyright 2014 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 runtime
     6  
     7  import (
     8  	"internal/abi"
     9  	"internal/cpu"
    10  	"internal/goarch"
    11  	"unsafe"
    12  )
    13  
    14  const (
    15  	c0 = uintptr((8-goarch.PtrSize)/4*2860486313 + (goarch.PtrSize-4)/4*33054211828000289)
    16  	c1 = uintptr((8-goarch.PtrSize)/4*3267000013 + (goarch.PtrSize-4)/4*23344194077549503)
    17  )
    18  
    19  func memhash0(p unsafe.Pointer, h uintptr) uintptr {
    20  	return h
    21  }
    22  
    23  func memhash8(p unsafe.Pointer, h uintptr) uintptr {
    24  	return memhash(p, h, 1)
    25  }
    26  
    27  func memhash16(p unsafe.Pointer, h uintptr) uintptr {
    28  	return memhash(p, h, 2)
    29  }
    30  
    31  func memhash128(p unsafe.Pointer, h uintptr) uintptr {
    32  	return memhash(p, h, 16)
    33  }
    34  
    35  //go:nosplit
    36  func memhash_varlen(p unsafe.Pointer, h uintptr) uintptr {
    37  	ptr := getclosureptr()
    38  	size := *(*uintptr)(unsafe.Pointer(ptr + unsafe.Sizeof(h)))
    39  	return memhash(p, h, size)
    40  }
    41  
    42  // runtime variable to check if the processor we're running on
    43  // actually supports the instructions used by the AES-based
    44  // hash implementation.
    45  var useAeshash bool
    46  
    47  // in asm_*.s
    48  
    49  // memhash should be an internal detail,
    50  // but widely used packages access it using linkname.
    51  // Notable members of the hall of shame include:
    52  //   - github.com/aacfactory/fns
    53  //   - github.com/dgraph-io/ristretto
    54  //   - github.com/minio/simdjson-go
    55  //   - github.com/nbd-wtf/go-nostr
    56  //   - github.com/outcaste-io/ristretto
    57  //   - github.com/puzpuzpuz/xsync/v2
    58  //   - github.com/puzpuzpuz/xsync/v3
    59  //   - github.com/segmentio/parquet-go
    60  //   - github.com/parquet-go/parquet-go
    61  //   - github.com/authzed/spicedb
    62  //   - github.com/pingcap/badger
    63  //
    64  // Do not remove or change the type signature.
    65  // See go.dev/issue/67401.
    66  //
    67  //go:linkname memhash
    68  func memhash(p unsafe.Pointer, h, s uintptr) uintptr
    69  
    70  // memhash32 should be an internal detail,
    71  // but widely used packages access it using linkname.
    72  // Notable members of the hall of shame include:
    73  //   - github.com/segmentio/parquet-go
    74  //   - github.com/parquet-go/parquet-go
    75  //
    76  // Do not remove or change the type signature.
    77  // See go.dev/issue/67401.
    78  //
    79  //go:linkname memhash32
    80  func memhash32(p unsafe.Pointer, h uintptr) uintptr
    81  
    82  // memhash64 should be an internal detail,
    83  // but widely used packages access it using linkname.
    84  // Notable members of the hall of shame include:
    85  //   - github.com/segmentio/parquet-go
    86  //   - github.com/parquet-go/parquet-go
    87  //
    88  // Do not remove or change the type signature.
    89  // See go.dev/issue/67401.
    90  //
    91  //go:linkname memhash64
    92  func memhash64(p unsafe.Pointer, h uintptr) uintptr
    93  
    94  // strhash should be an internal detail,
    95  // but widely used packages access it using linkname.
    96  // Notable members of the hall of shame include:
    97  //   - github.com/aristanetworks/goarista
    98  //   - github.com/bytedance/sonic
    99  //   - github.com/bytedance/go-tagexpr/v2
   100  //   - github.com/cloudwego/frugal
   101  //   - github.com/cloudwego/dynamicgo
   102  //   - github.com/v2fly/v2ray-core/v5
   103  //
   104  // Do not remove or change the type signature.
   105  // See go.dev/issue/67401.
   106  //
   107  //go:linkname strhash
   108  func strhash(p unsafe.Pointer, h uintptr) uintptr
   109  
   110  func strhashFallback(a unsafe.Pointer, h uintptr) uintptr {
   111  	x := (*stringStruct)(a)
   112  	return memhashFallback(x.str, h, uintptr(x.len))
   113  }
   114  
   115  // NOTE: Because NaN != NaN, a map can contain any
   116  // number of (mostly useless) entries keyed with NaNs.
   117  // To avoid long hash chains, we assign a random number
   118  // as the hash value for a NaN.
   119  
   120  func f32hash(p unsafe.Pointer, h uintptr) uintptr {
   121  	f := *(*float32)(p)
   122  	switch {
   123  	case f == 0:
   124  		return c1 * (c0 ^ h) // +0, -0
   125  	case f != f:
   126  		return c1 * (c0 ^ h ^ uintptr(rand())) // any kind of NaN
   127  	default:
   128  		return memhash(p, h, 4)
   129  	}
   130  }
   131  
   132  func f64hash(p unsafe.Pointer, h uintptr) uintptr {
   133  	f := *(*float64)(p)
   134  	switch {
   135  	case f == 0:
   136  		return c1 * (c0 ^ h) // +0, -0
   137  	case f != f:
   138  		return c1 * (c0 ^ h ^ uintptr(rand())) // any kind of NaN
   139  	default:
   140  		return memhash(p, h, 8)
   141  	}
   142  }
   143  
   144  func c64hash(p unsafe.Pointer, h uintptr) uintptr {
   145  	x := (*[2]float32)(p)
   146  	return f32hash(unsafe.Pointer(&x[1]), f32hash(unsafe.Pointer(&x[0]), h))
   147  }
   148  
   149  func c128hash(p unsafe.Pointer, h uintptr) uintptr {
   150  	x := (*[2]float64)(p)
   151  	return f64hash(unsafe.Pointer(&x[1]), f64hash(unsafe.Pointer(&x[0]), h))
   152  }
   153  
   154  func interhash(p unsafe.Pointer, h uintptr) uintptr {
   155  	a := (*iface)(p)
   156  	tab := a.tab
   157  	if tab == nil {
   158  		return h
   159  	}
   160  	t := tab.Type
   161  	if t.Equal == nil {
   162  		// Check hashability here. We could do this check inside
   163  		// typehash, but we want to report the topmost type in
   164  		// the error text (e.g. in a struct with a field of slice type
   165  		// we want to report the struct, not the slice).
   166  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   167  	}
   168  	if isDirectIface(t) {
   169  		return c1 * typehash(t, unsafe.Pointer(&a.data), h^c0)
   170  	} else {
   171  		return c1 * typehash(t, a.data, h^c0)
   172  	}
   173  }
   174  
   175  // nilinterhash should be an internal detail,
   176  // but widely used packages access it using linkname.
   177  // Notable members of the hall of shame include:
   178  //   - github.com/anacrolix/stm
   179  //   - github.com/aristanetworks/goarista
   180  //
   181  // Do not remove or change the type signature.
   182  // See go.dev/issue/67401.
   183  //
   184  //go:linkname nilinterhash
   185  func nilinterhash(p unsafe.Pointer, h uintptr) uintptr {
   186  	a := (*eface)(p)
   187  	t := a._type
   188  	if t == nil {
   189  		return h
   190  	}
   191  	if t.Equal == nil {
   192  		// See comment in interhash above.
   193  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   194  	}
   195  	if isDirectIface(t) {
   196  		return c1 * typehash(t, unsafe.Pointer(&a.data), h^c0)
   197  	} else {
   198  		return c1 * typehash(t, a.data, h^c0)
   199  	}
   200  }
   201  
   202  // typehash computes the hash of the object of type t at address p.
   203  // h is the seed.
   204  // This function is seldom used. Most maps use for hashing either
   205  // fixed functions (e.g. f32hash) or compiler-generated functions
   206  // (e.g. for a type like struct { x, y string }). This implementation
   207  // is slower but more general and is used for hashing interface types
   208  // (called from interhash or nilinterhash, above) or for hashing in
   209  // maps generated by reflect.MapOf (reflect_typehash, below).
   210  // Note: this function must match the compiler generated
   211  // functions exactly. See issue 37716.
   212  //
   213  // typehash should be an internal detail,
   214  // but widely used packages access it using linkname.
   215  // Notable members of the hall of shame include:
   216  //   - github.com/puzpuzpuz/xsync/v2
   217  //   - github.com/puzpuzpuz/xsync/v3
   218  //
   219  // Do not remove or change the type signature.
   220  // See go.dev/issue/67401.
   221  //
   222  //go:linkname typehash
   223  func typehash(t *_type, p unsafe.Pointer, h uintptr) uintptr {
   224  	if t.TFlag&abi.TFlagRegularMemory != 0 {
   225  		// Handle ptr sizes specially, see issue 37086.
   226  		switch t.Size_ {
   227  		case 4:
   228  			return memhash32(p, h)
   229  		case 8:
   230  			return memhash64(p, h)
   231  		default:
   232  			return memhash(p, h, t.Size_)
   233  		}
   234  	}
   235  	switch t.Kind_ & abi.KindMask {
   236  	case abi.Float32:
   237  		return f32hash(p, h)
   238  	case abi.Float64:
   239  		return f64hash(p, h)
   240  	case abi.Complex64:
   241  		return c64hash(p, h)
   242  	case abi.Complex128:
   243  		return c128hash(p, h)
   244  	case abi.String:
   245  		return strhash(p, h)
   246  	case abi.Interface:
   247  		i := (*interfacetype)(unsafe.Pointer(t))
   248  		if len(i.Methods) == 0 {
   249  			return nilinterhash(p, h)
   250  		}
   251  		return interhash(p, h)
   252  	case abi.Array:
   253  		a := (*arraytype)(unsafe.Pointer(t))
   254  		for i := uintptr(0); i < a.Len; i++ {
   255  			h = typehash(a.Elem, add(p, i*a.Elem.Size_), h)
   256  		}
   257  		return h
   258  	case abi.Struct:
   259  		s := (*structtype)(unsafe.Pointer(t))
   260  		for _, f := range s.Fields {
   261  			if f.Name.IsBlank() {
   262  				continue
   263  			}
   264  			h = typehash(f.Typ, add(p, f.Offset), h)
   265  		}
   266  		return h
   267  	default:
   268  		// Should never happen, as typehash should only be called
   269  		// with comparable types.
   270  		panic(errorString("hash of unhashable type " + toRType(t).string()))
   271  	}
   272  }
   273  
   274  func mapKeyError(t *maptype, p unsafe.Pointer) error {
   275  	if !t.HashMightPanic() {
   276  		return nil
   277  	}
   278  	return mapKeyError2(t.Key, p)
   279  }
   280  
   281  func mapKeyError2(t *_type, p unsafe.Pointer) error {
   282  	if t.TFlag&abi.TFlagRegularMemory != 0 {
   283  		return nil
   284  	}
   285  	switch t.Kind_ & abi.KindMask {
   286  	case abi.Float32, abi.Float64, abi.Complex64, abi.Complex128, abi.String:
   287  		return nil
   288  	case abi.Interface:
   289  		i := (*interfacetype)(unsafe.Pointer(t))
   290  		var t *_type
   291  		var pdata *unsafe.Pointer
   292  		if len(i.Methods) == 0 {
   293  			a := (*eface)(p)
   294  			t = a._type
   295  			if t == nil {
   296  				return nil
   297  			}
   298  			pdata = &a.data
   299  		} else {
   300  			a := (*iface)(p)
   301  			if a.tab == nil {
   302  				return nil
   303  			}
   304  			t = a.tab.Type
   305  			pdata = &a.data
   306  		}
   307  
   308  		if t.Equal == nil {
   309  			return errorString("hash of unhashable type " + toRType(t).string())
   310  		}
   311  
   312  		if isDirectIface(t) {
   313  			return mapKeyError2(t, unsafe.Pointer(pdata))
   314  		} else {
   315  			return mapKeyError2(t, *pdata)
   316  		}
   317  	case abi.Array:
   318  		a := (*arraytype)(unsafe.Pointer(t))
   319  		for i := uintptr(0); i < a.Len; i++ {
   320  			if err := mapKeyError2(a.Elem, add(p, i*a.Elem.Size_)); err != nil {
   321  				return err
   322  			}
   323  		}
   324  		return nil
   325  	case abi.Struct:
   326  		s := (*structtype)(unsafe.Pointer(t))
   327  		for _, f := range s.Fields {
   328  			if f.Name.IsBlank() {
   329  				continue
   330  			}
   331  			if err := mapKeyError2(f.Typ, add(p, f.Offset)); err != nil {
   332  				return err
   333  			}
   334  		}
   335  		return nil
   336  	default:
   337  		// Should never happen, keep this case for robustness.
   338  		return errorString("hash of unhashable type " + toRType(t).string())
   339  	}
   340  }
   341  
   342  //go:linkname reflect_typehash reflect.typehash
   343  func reflect_typehash(t *_type, p unsafe.Pointer, h uintptr) uintptr {
   344  	return typehash(t, p, h)
   345  }
   346  
   347  func memequal0(p, q unsafe.Pointer) bool {
   348  	return true
   349  }
   350  func memequal8(p, q unsafe.Pointer) bool {
   351  	return *(*int8)(p) == *(*int8)(q)
   352  }
   353  func memequal16(p, q unsafe.Pointer) bool {
   354  	return *(*int16)(p) == *(*int16)(q)
   355  }
   356  func memequal32(p, q unsafe.Pointer) bool {
   357  	return *(*int32)(p) == *(*int32)(q)
   358  }
   359  func memequal64(p, q unsafe.Pointer) bool {
   360  	return *(*int64)(p) == *(*int64)(q)
   361  }
   362  func memequal128(p, q unsafe.Pointer) bool {
   363  	return *(*[2]int64)(p) == *(*[2]int64)(q)
   364  }
   365  func f32equal(p, q unsafe.Pointer) bool {
   366  	return *(*float32)(p) == *(*float32)(q)
   367  }
   368  func f64equal(p, q unsafe.Pointer) bool {
   369  	return *(*float64)(p) == *(*float64)(q)
   370  }
   371  func c64equal(p, q unsafe.Pointer) bool {
   372  	return *(*complex64)(p) == *(*complex64)(q)
   373  }
   374  func c128equal(p, q unsafe.Pointer) bool {
   375  	return *(*complex128)(p) == *(*complex128)(q)
   376  }
   377  func strequal(p, q unsafe.Pointer) bool {
   378  	return *(*string)(p) == *(*string)(q)
   379  }
   380  func interequal(p, q unsafe.Pointer) bool {
   381  	x := *(*iface)(p)
   382  	y := *(*iface)(q)
   383  	return x.tab == y.tab && ifaceeq(x.tab, x.data, y.data)
   384  }
   385  func nilinterequal(p, q unsafe.Pointer) bool {
   386  	x := *(*eface)(p)
   387  	y := *(*eface)(q)
   388  	return x._type == y._type && efaceeq(x._type, x.data, y.data)
   389  }
   390  func efaceeq(t *_type, x, y unsafe.Pointer) bool {
   391  	if t == nil {
   392  		return true
   393  	}
   394  	eq := t.Equal
   395  	if eq == nil {
   396  		panic(errorString("comparing uncomparable type " + toRType(t).string()))
   397  	}
   398  	if isDirectIface(t) {
   399  		// Direct interface types are ptr, chan, map, func, and single-element structs/arrays thereof.
   400  		// Maps and funcs are not comparable, so they can't reach here.
   401  		// Ptrs, chans, and single-element items can be compared directly using ==.
   402  		return x == y
   403  	}
   404  	return eq(x, y)
   405  }
   406  func ifaceeq(tab *itab, x, y unsafe.Pointer) bool {
   407  	if tab == nil {
   408  		return true
   409  	}
   410  	t := tab.Type
   411  	eq := t.Equal
   412  	if eq == nil {
   413  		panic(errorString("comparing uncomparable type " + toRType(t).string()))
   414  	}
   415  	if isDirectIface(t) {
   416  		// See comment in efaceeq.
   417  		return x == y
   418  	}
   419  	return eq(x, y)
   420  }
   421  
   422  // Testing adapters for hash quality tests (see hash_test.go)
   423  //
   424  // stringHash should be an internal detail,
   425  // but widely used packages access it using linkname.
   426  // Notable members of the hall of shame include:
   427  //   - github.com/k14s/starlark-go
   428  //
   429  // Do not remove or change the type signature.
   430  // See go.dev/issue/67401.
   431  //
   432  //go:linkname stringHash
   433  func stringHash(s string, seed uintptr) uintptr {
   434  	return strhash(noescape(unsafe.Pointer(&s)), seed)
   435  }
   436  
   437  func bytesHash(b []byte, seed uintptr) uintptr {
   438  	s := (*slice)(unsafe.Pointer(&b))
   439  	return memhash(s.array, seed, uintptr(s.len))
   440  }
   441  
   442  func int32Hash(i uint32, seed uintptr) uintptr {
   443  	return memhash32(noescape(unsafe.Pointer(&i)), seed)
   444  }
   445  
   446  func int64Hash(i uint64, seed uintptr) uintptr {
   447  	return memhash64(noescape(unsafe.Pointer(&i)), seed)
   448  }
   449  
   450  func efaceHash(i any, seed uintptr) uintptr {
   451  	return nilinterhash(noescape(unsafe.Pointer(&i)), seed)
   452  }
   453  
   454  func ifaceHash(i interface {
   455  	F()
   456  }, seed uintptr) uintptr {
   457  	return interhash(noescape(unsafe.Pointer(&i)), seed)
   458  }
   459  
   460  const hashRandomBytes = goarch.PtrSize / 4 * 64
   461  
   462  // used in asm_{386,amd64,arm64}.s to seed the hash function
   463  var aeskeysched [hashRandomBytes]byte
   464  
   465  // used in hash{32,64}.go to seed the hash function
   466  var hashkey [4]uintptr
   467  
   468  func alginit() {
   469  	// Install AES hash algorithms if the instructions needed are present.
   470  	if (GOARCH == "386" || GOARCH == "amd64") &&
   471  		cpu.X86.HasAES && // AESENC
   472  		cpu.X86.HasSSSE3 && // PSHUFB
   473  		cpu.X86.HasSSE41 { // PINSR{D,Q}
   474  		initAlgAES()
   475  		return
   476  	}
   477  	if GOARCH == "arm64" && cpu.ARM64.HasAES {
   478  		initAlgAES()
   479  		return
   480  	}
   481  	for i := range hashkey {
   482  		hashkey[i] = uintptr(bootstrapRand())
   483  	}
   484  }
   485  
   486  func initAlgAES() {
   487  	useAeshash = true
   488  	// Initialize with random data so hash collisions will be hard to engineer.
   489  	key := (*[hashRandomBytes / 8]uint64)(unsafe.Pointer(&aeskeysched))
   490  	for i := range key {
   491  		key[i] = bootstrapRand()
   492  	}
   493  }
   494  
   495  // Note: These routines perform the read with a native endianness.
   496  func readUnaligned32(p unsafe.Pointer) uint32 {
   497  	q := (*[4]byte)(p)
   498  	if goarch.BigEndian {
   499  		return uint32(q[3]) | uint32(q[2])<<8 | uint32(q[1])<<16 | uint32(q[0])<<24
   500  	}
   501  	return uint32(q[0]) | uint32(q[1])<<8 | uint32(q[2])<<16 | uint32(q[3])<<24
   502  }
   503  
   504  func readUnaligned64(p unsafe.Pointer) uint64 {
   505  	q := (*[8]byte)(p)
   506  	if goarch.BigEndian {
   507  		return uint64(q[7]) | uint64(q[6])<<8 | uint64(q[5])<<16 | uint64(q[4])<<24 |
   508  			uint64(q[3])<<32 | uint64(q[2])<<40 | uint64(q[1])<<48 | uint64(q[0])<<56
   509  	}
   510  	return uint64(q[0]) | uint64(q[1])<<8 | uint64(q[2])<<16 | uint64(q[3])<<24 | uint64(q[4])<<32 | uint64(q[5])<<40 | uint64(q[6])<<48 | uint64(q[7])<<56
   511  }
   512
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