prog.go

Documentation: cmd/compile/internal/objw

     1  // Derived from Inferno utils/6c/txt.c
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6c/txt.c
     3  //
     4  //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
     5  //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
     6  //	Portions Copyright © 1997-1999 Vita Nuova Limited
     7  //	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
     8  //	Portions Copyright © 2004,2006 Bruce Ellis
     9  //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
    10  //	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
    11  //	Portions Copyright © 2009 The Go Authors. All rights reserved.
    12  //
    13  // Permission is hereby granted, free of charge, to any person obtaining a copy
    14  // of this software and associated documentation files (the "Software"), to deal
    15  // in the Software without restriction, including without limitation the rights
    16  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    17  // copies of the Software, and to permit persons to whom the Software is
    18  // furnished to do so, subject to the following conditions:
    19  //
    20  // The above copyright notice and this permission notice shall be included in
    21  // all copies or substantial portions of the Software.
    22  //
    23  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    24  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    25  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    26  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    27  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    28  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    29  // THE SOFTWARE.
    30  
    31  package objw
    32  
    33  import (
    34  	"cmd/compile/internal/base"
    35  	"cmd/compile/internal/ir"
    36  	"cmd/internal/obj"
    37  	"cmd/internal/src"
    38  	"internal/abi"
    39  )
    40  
    41  var sharedProgArray = new([10000]obj.Prog) // *T instead of T to work around issue 19839
    42  
    43  // NewProgs returns a new Progs for fn.
    44  // worker indicates which of the backend workers will use the Progs.
    45  func NewProgs(fn *ir.Func, worker int) *Progs {
    46  	pp := new(Progs)
    47  	if base.Ctxt.CanReuseProgs() {
    48  		sz := len(sharedProgArray) / base.Flag.LowerC
    49  		pp.Cache = sharedProgArray[sz*worker : sz*(worker+1)]
    50  	}
    51  	pp.CurFunc = fn
    52  
    53  	// prime the pump
    54  	pp.Next = pp.NewProg()
    55  	pp.Clear(pp.Next)
    56  
    57  	pp.Pos = fn.Pos()
    58  	pp.SetText(fn)
    59  	// PCDATA tables implicitly start with index -1.
    60  	pp.PrevLive = -1
    61  	pp.NextLive = pp.PrevLive
    62  	pp.NextUnsafe = pp.PrevUnsafe
    63  	return pp
    64  }
    65  
    66  // Progs accumulates Progs for a function and converts them into machine code.
    67  type Progs struct {
    68  	Text       *obj.Prog  // ATEXT Prog for this function
    69  	Next       *obj.Prog  // next Prog
    70  	PC         int64      // virtual PC; count of Progs
    71  	Pos        src.XPos   // position to use for new Progs
    72  	CurFunc    *ir.Func   // fn these Progs are for
    73  	Cache      []obj.Prog // local progcache
    74  	CacheIndex int        // first free element of progcache
    75  
    76  	NextLive StackMapIndex // liveness index for the next Prog
    77  	PrevLive StackMapIndex // last emitted liveness index
    78  
    79  	NextUnsafe bool // unsafe mark for the next Prog
    80  	PrevUnsafe bool // last emitted unsafe mark
    81  }
    82  
    83  type StackMapIndex int
    84  
    85  // StackMapDontCare indicates that the stack map index at a Value
    86  // doesn't matter.
    87  //
    88  // This is a sentinel value that should never be emitted to the PCDATA
    89  // stream. We use -1000 because that's obviously never a valid stack
    90  // index (but -1 is).
    91  const StackMapDontCare StackMapIndex = -1000
    92  
    93  func (s StackMapIndex) StackMapValid() bool {
    94  	return s != StackMapDontCare
    95  }
    96  
    97  func (pp *Progs) NewProg() *obj.Prog {
    98  	var p *obj.Prog
    99  	if pp.CacheIndex < len(pp.Cache) {
   100  		p = &pp.Cache[pp.CacheIndex]
   101  		pp.CacheIndex++
   102  	} else {
   103  		p = new(obj.Prog)
   104  	}
   105  	p.Ctxt = base.Ctxt
   106  	return p
   107  }
   108  
   109  // Flush converts from pp to machine code.
   110  func (pp *Progs) Flush() {
   111  	plist := &obj.Plist{Firstpc: pp.Text, Curfn: pp.CurFunc}
   112  	obj.Flushplist(base.Ctxt, plist, pp.NewProg)
   113  }
   114  
   115  // Free clears pp and any associated resources.
   116  func (pp *Progs) Free() {
   117  	if base.Ctxt.CanReuseProgs() {
   118  		// Clear progs to enable GC and avoid abuse.
   119  		s := pp.Cache[:pp.CacheIndex]
   120  		for i := range s {
   121  			s[i] = obj.Prog{}
   122  		}
   123  	}
   124  	// Clear pp to avoid abuse.
   125  	*pp = Progs{}
   126  }
   127  
   128  // Prog adds a Prog with instruction As to pp.
   129  func (pp *Progs) Prog(as obj.As) *obj.Prog {
   130  	if pp.NextLive != StackMapDontCare && pp.NextLive != pp.PrevLive {
   131  		// Emit stack map index change.
   132  		idx := pp.NextLive
   133  		pp.PrevLive = idx
   134  		p := pp.Prog(obj.APCDATA)
   135  		p.From.SetConst(abi.PCDATA_StackMapIndex)
   136  		p.To.SetConst(int64(idx))
   137  	}
   138  	if pp.NextUnsafe != pp.PrevUnsafe {
   139  		// Emit unsafe-point marker.
   140  		pp.PrevUnsafe = pp.NextUnsafe
   141  		p := pp.Prog(obj.APCDATA)
   142  		p.From.SetConst(abi.PCDATA_UnsafePoint)
   143  		if pp.NextUnsafe {
   144  			p.To.SetConst(abi.UnsafePointUnsafe)
   145  		} else {
   146  			p.To.SetConst(abi.UnsafePointSafe)
   147  		}
   148  	}
   149  
   150  	p := pp.Next
   151  	pp.Next = pp.NewProg()
   152  	pp.Clear(pp.Next)
   153  	p.Link = pp.Next
   154  
   155  	if !pp.Pos.IsKnown() && base.Flag.K != 0 {
   156  		base.Warn("prog: unknown position (line 0)")
   157  	}
   158  
   159  	p.As = as
   160  	p.Pos = pp.Pos
   161  	if pp.Pos.IsStmt() == src.PosIsStmt {
   162  		// Clear IsStmt for later Progs at this pos provided that as can be marked as a stmt
   163  		if LosesStmtMark(as) {
   164  			return p
   165  		}
   166  		pp.Pos = pp.Pos.WithNotStmt()
   167  	}
   168  	return p
   169  }
   170  
   171  func (pp *Progs) Clear(p *obj.Prog) {
   172  	obj.Nopout(p)
   173  	p.As = obj.AEND
   174  	p.Pc = pp.PC
   175  	pp.PC++
   176  }
   177  
   178  func (pp *Progs) Append(p *obj.Prog, as obj.As, ftype obj.AddrType, freg int16, foffset int64, ttype obj.AddrType, treg int16, toffset int64) *obj.Prog {
   179  	q := pp.NewProg()
   180  	pp.Clear(q)
   181  	q.As = as
   182  	q.Pos = p.Pos
   183  	q.From.Type = ftype
   184  	q.From.Reg = freg
   185  	q.From.Offset = foffset
   186  	q.To.Type = ttype
   187  	q.To.Reg = treg
   188  	q.To.Offset = toffset
   189  	q.Link = p.Link
   190  	p.Link = q
   191  	return q
   192  }
   193  
   194  func (pp *Progs) SetText(fn *ir.Func) {
   195  	if pp.Text != nil {
   196  		base.Fatalf("Progs.SetText called twice")
   197  	}
   198  	ptxt := pp.Prog(obj.ATEXT)
   199  	pp.Text = ptxt
   200  
   201  	fn.LSym.Func().Text = ptxt
   202  	ptxt.From.Type = obj.TYPE_MEM
   203  	ptxt.From.Name = obj.NAME_EXTERN
   204  	ptxt.From.Sym = fn.LSym
   205  }
   206  
   207  // LosesStmtMark reports whether a prog with op as loses its statement mark on the way to DWARF.
   208  // The attributes from some opcodes are lost in translation.
   209  // TODO: this is an artifact of how funcpctab combines information for instructions at a single PC.
   210  // Should try to fix it there.
   211  func LosesStmtMark(as obj.As) bool {
   212  	// is_stmt does not work for these; it DOES for ANOP even though that generates no code.
   213  	return as == obj.APCDATA || as == obj.AFUNCDATA
   214  }
   215
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