github.com/bir3/gocompiler@v0.3.205/src/cmd/compile/internal/ssa/value.go (about)

     1  // Copyright 2015 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 ssa
     6  
     7  import (
     8  	"github.com/bir3/gocompiler/src/cmd/compile/internal/ir"
     9  	"github.com/bir3/gocompiler/src/cmd/compile/internal/types"
    10  	"github.com/bir3/gocompiler/src/cmd/internal/src"
    11  	"fmt"
    12  	"math"
    13  	"sort"
    14  	"strings"
    15  )
    16  
    17  // A Value represents a value in the SSA representation of the program.
    18  // The ID and Type fields must not be modified. The remainder may be modified
    19  // if they preserve the value of the Value (e.g. changing a (mul 2 x) to an (add x x)).
    20  type Value struct {
    21  	// A unique identifier for the value. For performance we allocate these IDs
    22  	// densely starting at 1.  There is no guarantee that there won't be occasional holes, though.
    23  	ID ID
    24  
    25  	// The operation that computes this value. See op.go.
    26  	Op Op
    27  
    28  	// The type of this value. Normally this will be a Go type, but there
    29  	// are a few other pseudo-types, see ../types/type.go.
    30  	Type *types.Type
    31  
    32  	// Auxiliary info for this value. The type of this information depends on the opcode and type.
    33  	// AuxInt is used for integer values, Aux is used for other values.
    34  	// Floats are stored in AuxInt using math.Float64bits(f).
    35  	// Unused portions of AuxInt are filled by sign-extending the used portion,
    36  	// even if the represented value is unsigned.
    37  	// Users of AuxInt which interpret AuxInt as unsigned (e.g. shifts) must be careful.
    38  	// Use Value.AuxUnsigned to get the zero-extended value of AuxInt.
    39  	AuxInt int64
    40  	Aux    Aux
    41  
    42  	// Arguments of this value
    43  	Args []*Value
    44  
    45  	// Containing basic block
    46  	Block *Block
    47  
    48  	// Source position
    49  	Pos src.XPos
    50  
    51  	// Use count. Each appearance in Value.Args and Block.Controls counts once.
    52  	Uses int32
    53  
    54  	// wasm: Value stays on the WebAssembly stack. This value will not get a "register" (WebAssembly variable)
    55  	// nor a slot on Go stack, and the generation of this value is delayed to its use time.
    56  	OnWasmStack bool
    57  
    58  	// Is this value in the per-function constant cache? If so, remove from cache before changing it or recycling it.
    59  	InCache bool
    60  
    61  	// Storage for the first three args
    62  	argstorage [3]*Value
    63  }
    64  
    65  // Examples:
    66  // Opcode          aux   args
    67  //  OpAdd          nil      2
    68  //  OpConst     string      0    string constant
    69  //  OpConst      int64      0    int64 constant
    70  //  OpAddcq      int64      1    amd64 op: v = arg[0] + constant
    71  
    72  // short form print. Just v#.
    73  func (v *Value) String() string {
    74  	if v == nil {
    75  		return "nil" // should never happen, but not panicking helps with debugging
    76  	}
    77  	return fmt.Sprintf("v%d", v.ID)
    78  }
    79  
    80  func (v *Value) AuxInt8() int8 {
    81  	if opcodeTable[v.Op].auxType != auxInt8 && opcodeTable[v.Op].auxType != auxNameOffsetInt8 {
    82  		v.Fatalf("op %s doesn't have an int8 aux field", v.Op)
    83  	}
    84  	return int8(v.AuxInt)
    85  }
    86  
    87  func (v *Value) AuxInt16() int16 {
    88  	if opcodeTable[v.Op].auxType != auxInt16 {
    89  		v.Fatalf("op %s doesn't have an int16 aux field", v.Op)
    90  	}
    91  	return int16(v.AuxInt)
    92  }
    93  
    94  func (v *Value) AuxInt32() int32 {
    95  	if opcodeTable[v.Op].auxType != auxInt32 {
    96  		v.Fatalf("op %s doesn't have an int32 aux field", v.Op)
    97  	}
    98  	return int32(v.AuxInt)
    99  }
   100  
   101  // AuxUnsigned returns v.AuxInt as an unsigned value for OpConst*.
   102  // v.AuxInt is always sign-extended to 64 bits, even if the
   103  // represented value is unsigned. This undoes that sign extension.
   104  func (v *Value) AuxUnsigned() uint64 {
   105  	c := v.AuxInt
   106  	switch v.Op {
   107  	case OpConst64:
   108  		return uint64(c)
   109  	case OpConst32:
   110  		return uint64(uint32(c))
   111  	case OpConst16:
   112  		return uint64(uint16(c))
   113  	case OpConst8:
   114  		return uint64(uint8(c))
   115  	}
   116  	v.Fatalf("op %s isn't OpConst*", v.Op)
   117  	return 0
   118  }
   119  
   120  func (v *Value) AuxFloat() float64 {
   121  	if opcodeTable[v.Op].auxType != auxFloat32 && opcodeTable[v.Op].auxType != auxFloat64 {
   122  		v.Fatalf("op %s doesn't have a float aux field", v.Op)
   123  	}
   124  	return math.Float64frombits(uint64(v.AuxInt))
   125  }
   126  func (v *Value) AuxValAndOff() ValAndOff {
   127  	if opcodeTable[v.Op].auxType != auxSymValAndOff {
   128  		v.Fatalf("op %s doesn't have a ValAndOff aux field", v.Op)
   129  	}
   130  	return ValAndOff(v.AuxInt)
   131  }
   132  
   133  func (v *Value) AuxArm64BitField() arm64BitField {
   134  	if opcodeTable[v.Op].auxType != auxARM64BitField {
   135  		v.Fatalf("op %s doesn't have a ValAndOff aux field", v.Op)
   136  	}
   137  	return arm64BitField(v.AuxInt)
   138  }
   139  
   140  // long form print.  v# = opcode <type> [aux] args [: reg] (names)
   141  func (v *Value) LongString() string {
   142  	if v == nil {
   143  		return "<NIL VALUE>"
   144  	}
   145  	s := fmt.Sprintf("v%d = %s", v.ID, v.Op)
   146  	s += " <" + v.Type.String() + ">"
   147  	s += v.auxString()
   148  	for _, a := range v.Args {
   149  		s += fmt.Sprintf(" %v", a)
   150  	}
   151  	if v.Block == nil {
   152  		return s
   153  	}
   154  	r := v.Block.Func.RegAlloc
   155  	if int(v.ID) < len(r) && r[v.ID] != nil {
   156  		s += " : " + r[v.ID].String()
   157  	}
   158  	if reg := v.Block.Func.tempRegs[v.ID]; reg != nil {
   159  		s += " tmp=" + reg.String()
   160  	}
   161  	var names []string
   162  	for name, values := range v.Block.Func.NamedValues {
   163  		for _, value := range values {
   164  			if value == v {
   165  				names = append(names, name.String())
   166  				break // drop duplicates.
   167  			}
   168  		}
   169  	}
   170  	if len(names) != 0 {
   171  		sort.Strings(names) // Otherwise a source of variation in debugging output.
   172  		s += " (" + strings.Join(names, ", ") + ")"
   173  	}
   174  	return s
   175  }
   176  
   177  func (v *Value) auxString() string {
   178  	switch opcodeTable[v.Op].auxType {
   179  	case auxBool:
   180  		if v.AuxInt == 0 {
   181  			return " [false]"
   182  		} else {
   183  			return " [true]"
   184  		}
   185  	case auxInt8:
   186  		return fmt.Sprintf(" [%d]", v.AuxInt8())
   187  	case auxInt16:
   188  		return fmt.Sprintf(" [%d]", v.AuxInt16())
   189  	case auxInt32:
   190  		return fmt.Sprintf(" [%d]", v.AuxInt32())
   191  	case auxInt64, auxInt128:
   192  		return fmt.Sprintf(" [%d]", v.AuxInt)
   193  	case auxARM64BitField:
   194  		lsb := v.AuxArm64BitField().getARM64BFlsb()
   195  		width := v.AuxArm64BitField().getARM64BFwidth()
   196  		return fmt.Sprintf(" [lsb=%d,width=%d]", lsb, width)
   197  	case auxFloat32, auxFloat64:
   198  		return fmt.Sprintf(" [%g]", v.AuxFloat())
   199  	case auxString:
   200  		return fmt.Sprintf(" {%q}", v.Aux)
   201  	case auxSym, auxCall, auxTyp:
   202  		if v.Aux != nil {
   203  			return fmt.Sprintf(" {%v}", v.Aux)
   204  		}
   205  	case auxSymOff, auxCallOff, auxTypSize, auxNameOffsetInt8:
   206  		s := ""
   207  		if v.Aux != nil {
   208  			s = fmt.Sprintf(" {%v}", v.Aux)
   209  		}
   210  		if v.AuxInt != 0 || opcodeTable[v.Op].auxType == auxNameOffsetInt8 {
   211  			s += fmt.Sprintf(" [%v]", v.AuxInt)
   212  		}
   213  		return s
   214  	case auxSymValAndOff:
   215  		s := ""
   216  		if v.Aux != nil {
   217  			s = fmt.Sprintf(" {%v}", v.Aux)
   218  		}
   219  		return s + fmt.Sprintf(" [%s]", v.AuxValAndOff())
   220  	case auxCCop:
   221  		return fmt.Sprintf(" {%s}", Op(v.AuxInt))
   222  	case auxS390XCCMask, auxS390XRotateParams:
   223  		return fmt.Sprintf(" {%v}", v.Aux)
   224  	case auxFlagConstant:
   225  		return fmt.Sprintf("[%s]", flagConstant(v.AuxInt))
   226  	}
   227  	return ""
   228  }
   229  
   230  // If/when midstack inlining is enabled (-l=4), the compiler gets both larger and slower.
   231  // Not-inlining this method is a help (*Value.reset and *Block.NewValue0 are similar).
   232  //
   233  //go:noinline
   234  func (v *Value) AddArg(w *Value) {
   235  	if v.Args == nil {
   236  		v.resetArgs() // use argstorage
   237  	}
   238  	v.Args = append(v.Args, w)
   239  	w.Uses++
   240  }
   241  
   242  //go:noinline
   243  func (v *Value) AddArg2(w1, w2 *Value) {
   244  	if v.Args == nil {
   245  		v.resetArgs() // use argstorage
   246  	}
   247  	v.Args = append(v.Args, w1, w2)
   248  	w1.Uses++
   249  	w2.Uses++
   250  }
   251  
   252  //go:noinline
   253  func (v *Value) AddArg3(w1, w2, w3 *Value) {
   254  	if v.Args == nil {
   255  		v.resetArgs() // use argstorage
   256  	}
   257  	v.Args = append(v.Args, w1, w2, w3)
   258  	w1.Uses++
   259  	w2.Uses++
   260  	w3.Uses++
   261  }
   262  
   263  //go:noinline
   264  func (v *Value) AddArg4(w1, w2, w3, w4 *Value) {
   265  	v.Args = append(v.Args, w1, w2, w3, w4)
   266  	w1.Uses++
   267  	w2.Uses++
   268  	w3.Uses++
   269  	w4.Uses++
   270  }
   271  
   272  //go:noinline
   273  func (v *Value) AddArg5(w1, w2, w3, w4, w5 *Value) {
   274  	v.Args = append(v.Args, w1, w2, w3, w4, w5)
   275  	w1.Uses++
   276  	w2.Uses++
   277  	w3.Uses++
   278  	w4.Uses++
   279  	w5.Uses++
   280  }
   281  
   282  //go:noinline
   283  func (v *Value) AddArg6(w1, w2, w3, w4, w5, w6 *Value) {
   284  	v.Args = append(v.Args, w1, w2, w3, w4, w5, w6)
   285  	w1.Uses++
   286  	w2.Uses++
   287  	w3.Uses++
   288  	w4.Uses++
   289  	w5.Uses++
   290  	w6.Uses++
   291  }
   292  
   293  func (v *Value) AddArgs(a ...*Value) {
   294  	if v.Args == nil {
   295  		v.resetArgs() // use argstorage
   296  	}
   297  	v.Args = append(v.Args, a...)
   298  	for _, x := range a {
   299  		x.Uses++
   300  	}
   301  }
   302  func (v *Value) SetArg(i int, w *Value) {
   303  	v.Args[i].Uses--
   304  	v.Args[i] = w
   305  	w.Uses++
   306  }
   307  func (v *Value) SetArgs1(a *Value) {
   308  	v.resetArgs()
   309  	v.AddArg(a)
   310  }
   311  func (v *Value) SetArgs2(a, b *Value) {
   312  	v.resetArgs()
   313  	v.AddArg(a)
   314  	v.AddArg(b)
   315  }
   316  func (v *Value) SetArgs3(a, b, c *Value) {
   317  	v.resetArgs()
   318  	v.AddArg(a)
   319  	v.AddArg(b)
   320  	v.AddArg(c)
   321  }
   322  
   323  func (v *Value) resetArgs() {
   324  	for _, a := range v.Args {
   325  		a.Uses--
   326  	}
   327  	v.argstorage[0] = nil
   328  	v.argstorage[1] = nil
   329  	v.argstorage[2] = nil
   330  	v.Args = v.argstorage[:0]
   331  }
   332  
   333  // reset is called from most rewrite rules.
   334  // Allowing it to be inlined increases the size
   335  // of cmd/compile by almost 10%, and slows it down.
   336  //
   337  //go:noinline
   338  func (v *Value) reset(op Op) {
   339  	if v.InCache {
   340  		v.Block.Func.unCache(v)
   341  	}
   342  	v.Op = op
   343  	v.resetArgs()
   344  	v.AuxInt = 0
   345  	v.Aux = nil
   346  }
   347  
   348  // invalidateRecursively marks a value as invalid (unused)
   349  // and after decrementing reference counts on its Args,
   350  // also recursively invalidates any of those whose use
   351  // count goes to zero.  It returns whether any of the
   352  // invalidated values was marked with IsStmt.
   353  //
   354  // BEWARE of doing this *before* you've applied intended
   355  // updates to SSA.
   356  func (v *Value) invalidateRecursively() bool {
   357  	lostStmt := v.Pos.IsStmt() == src.PosIsStmt
   358  	if v.InCache {
   359  		v.Block.Func.unCache(v)
   360  	}
   361  	v.Op = OpInvalid
   362  
   363  	for _, a := range v.Args {
   364  		a.Uses--
   365  		if a.Uses == 0 {
   366  			lost := a.invalidateRecursively()
   367  			lostStmt = lost || lostStmt
   368  		}
   369  	}
   370  
   371  	v.argstorage[0] = nil
   372  	v.argstorage[1] = nil
   373  	v.argstorage[2] = nil
   374  	v.Args = v.argstorage[:0]
   375  
   376  	v.AuxInt = 0
   377  	v.Aux = nil
   378  	return lostStmt
   379  }
   380  
   381  // copyOf is called from rewrite rules.
   382  // It modifies v to be (Copy a).
   383  //
   384  //go:noinline
   385  func (v *Value) copyOf(a *Value) {
   386  	if v == a {
   387  		return
   388  	}
   389  	if v.InCache {
   390  		v.Block.Func.unCache(v)
   391  	}
   392  	v.Op = OpCopy
   393  	v.resetArgs()
   394  	v.AddArg(a)
   395  	v.AuxInt = 0
   396  	v.Aux = nil
   397  	v.Type = a.Type
   398  }
   399  
   400  // copyInto makes a new value identical to v and adds it to the end of b.
   401  // unlike copyIntoWithXPos this does not check for v.Pos being a statement.
   402  func (v *Value) copyInto(b *Block) *Value {
   403  	c := b.NewValue0(v.Pos.WithNotStmt(), v.Op, v.Type) // Lose the position, this causes line number churn otherwise.
   404  	c.Aux = v.Aux
   405  	c.AuxInt = v.AuxInt
   406  	c.AddArgs(v.Args...)
   407  	for _, a := range v.Args {
   408  		if a.Type.IsMemory() {
   409  			v.Fatalf("can't move a value with a memory arg %s", v.LongString())
   410  		}
   411  	}
   412  	return c
   413  }
   414  
   415  // copyIntoWithXPos makes a new value identical to v and adds it to the end of b.
   416  // The supplied position is used as the position of the new value.
   417  // Because this is used for rematerialization, check for case that (rematerialized)
   418  // input to value with position 'pos' carried a statement mark, and that the supplied
   419  // position (of the instruction using the rematerialized value) is not marked, and
   420  // preserve that mark if its line matches the supplied position.
   421  func (v *Value) copyIntoWithXPos(b *Block, pos src.XPos) *Value {
   422  	if v.Pos.IsStmt() == src.PosIsStmt && pos.IsStmt() != src.PosIsStmt && v.Pos.SameFileAndLine(pos) {
   423  		pos = pos.WithIsStmt()
   424  	}
   425  	c := b.NewValue0(pos, v.Op, v.Type)
   426  	c.Aux = v.Aux
   427  	c.AuxInt = v.AuxInt
   428  	c.AddArgs(v.Args...)
   429  	for _, a := range v.Args {
   430  		if a.Type.IsMemory() {
   431  			v.Fatalf("can't move a value with a memory arg %s", v.LongString())
   432  		}
   433  	}
   434  	return c
   435  }
   436  
   437  func (v *Value) Logf(msg string, args ...interface{}) { v.Block.Logf(msg, args...) }
   438  func (v *Value) Log() bool                            { return v.Block.Log() }
   439  func (v *Value) Fatalf(msg string, args ...interface{}) {
   440  	v.Block.Func.fe.Fatalf(v.Pos, msg, args...)
   441  }
   442  
   443  // isGenericIntConst reports whether v is a generic integer constant.
   444  func (v *Value) isGenericIntConst() bool {
   445  	return v != nil && (v.Op == OpConst64 || v.Op == OpConst32 || v.Op == OpConst16 || v.Op == OpConst8)
   446  }
   447  
   448  // ResultReg returns the result register assigned to v, in cmd/internal/obj/$ARCH numbering.
   449  // It is similar to Reg and Reg0, except that it is usable interchangeably for all Value Ops.
   450  // If you know v.Op, using Reg or Reg0 (as appropriate) will be more efficient.
   451  func (v *Value) ResultReg() int16 {
   452  	reg := v.Block.Func.RegAlloc[v.ID]
   453  	if reg == nil {
   454  		v.Fatalf("nil reg for value: %s\n%s\n", v.LongString(), v.Block.Func)
   455  	}
   456  	if pair, ok := reg.(LocPair); ok {
   457  		reg = pair[0]
   458  	}
   459  	if reg == nil {
   460  		v.Fatalf("nil reg0 for value: %s\n%s\n", v.LongString(), v.Block.Func)
   461  	}
   462  	return reg.(*Register).objNum
   463  }
   464  
   465  // Reg returns the register assigned to v, in cmd/internal/obj/$ARCH numbering.
   466  func (v *Value) Reg() int16 {
   467  	reg := v.Block.Func.RegAlloc[v.ID]
   468  	if reg == nil {
   469  		v.Fatalf("nil register for value: %s\n%s\n", v.LongString(), v.Block.Func)
   470  	}
   471  	return reg.(*Register).objNum
   472  }
   473  
   474  // Reg0 returns the register assigned to the first output of v, in cmd/internal/obj/$ARCH numbering.
   475  func (v *Value) Reg0() int16 {
   476  	reg := v.Block.Func.RegAlloc[v.ID].(LocPair)[0]
   477  	if reg == nil {
   478  		v.Fatalf("nil first register for value: %s\n%s\n", v.LongString(), v.Block.Func)
   479  	}
   480  	return reg.(*Register).objNum
   481  }
   482  
   483  // Reg1 returns the register assigned to the second output of v, in cmd/internal/obj/$ARCH numbering.
   484  func (v *Value) Reg1() int16 {
   485  	reg := v.Block.Func.RegAlloc[v.ID].(LocPair)[1]
   486  	if reg == nil {
   487  		v.Fatalf("nil second register for value: %s\n%s\n", v.LongString(), v.Block.Func)
   488  	}
   489  	return reg.(*Register).objNum
   490  }
   491  
   492  // RegTmp returns the temporary register assigned to v, in cmd/internal/obj/$ARCH numbering.
   493  func (v *Value) RegTmp() int16 {
   494  	reg := v.Block.Func.tempRegs[v.ID]
   495  	if reg == nil {
   496  		v.Fatalf("nil tmp register for value: %s\n%s\n", v.LongString(), v.Block.Func)
   497  	}
   498  	return reg.objNum
   499  }
   500  
   501  func (v *Value) RegName() string {
   502  	reg := v.Block.Func.RegAlloc[v.ID]
   503  	if reg == nil {
   504  		v.Fatalf("nil register for value: %s\n%s\n", v.LongString(), v.Block.Func)
   505  	}
   506  	return reg.(*Register).name
   507  }
   508  
   509  // MemoryArg returns the memory argument for the Value.
   510  // The returned value, if non-nil, will be memory-typed (or a tuple with a memory-typed second part).
   511  // Otherwise, nil is returned.
   512  func (v *Value) MemoryArg() *Value {
   513  	if v.Op == OpPhi {
   514  		v.Fatalf("MemoryArg on Phi")
   515  	}
   516  	na := len(v.Args)
   517  	if na == 0 {
   518  		return nil
   519  	}
   520  	if m := v.Args[na-1]; m.Type.IsMemory() {
   521  		return m
   522  	}
   523  	return nil
   524  }
   525  
   526  // LackingPos indicates whether v is a value that is unlikely to have a correct
   527  // position assigned to it.  Ignoring such values leads to more user-friendly positions
   528  // assigned to nearby values and the blocks containing them.
   529  func (v *Value) LackingPos() bool {
   530  	// The exact definition of LackingPos is somewhat heuristically defined and may change
   531  	// in the future, for example if some of these operations are generated more carefully
   532  	// with respect to their source position.
   533  	return v.Op == OpVarDef || v.Op == OpVarLive || v.Op == OpPhi ||
   534  		(v.Op == OpFwdRef || v.Op == OpCopy) && v.Type == types.TypeMem
   535  }
   536  
   537  // removeable reports whether the value v can be removed from the SSA graph entirely
   538  // if its use count drops to 0.
   539  func (v *Value) removeable() bool {
   540  	if v.Type.IsVoid() {
   541  		// Void ops, like nil pointer checks, must stay.
   542  		return false
   543  	}
   544  	if v.Type.IsMemory() {
   545  		// We don't need to preserve all memory ops, but we do need
   546  		// to keep calls at least (because they might have
   547  		// synchronization operations we can't see).
   548  		return false
   549  	}
   550  	if v.Op.HasSideEffects() {
   551  		// These are mostly synchronization operations.
   552  		return false
   553  	}
   554  	return true
   555  }
   556  
   557  // TODO(mdempsky): Shouldn't be necessary; see discussion at golang.org/cl/275756
   558  func (*Value) CanBeAnSSAAux() {}
   559  
   560  // AutoVar returns a *Name and int64 representing the auto variable and offset within it
   561  // where v should be spilled.
   562  func AutoVar(v *Value) (*ir.Name, int64) {
   563  	if loc, ok := v.Block.Func.RegAlloc[v.ID].(LocalSlot); ok {
   564  		if v.Type.Size() > loc.Type.Size() {
   565  			v.Fatalf("spill/restore type %s doesn't fit in slot type %s", v.Type, loc.Type)
   566  		}
   567  		return loc.N, loc.Off
   568  	}
   569  	// Assume it is a register, return its spill slot, which needs to be live
   570  	nameOff := v.Aux.(*AuxNameOffset)
   571  	return nameOff.Name, nameOff.Offset
   572  }