pass.go

Documentation: cmd/internal/obj

     1  // Inferno utils/6l/pass.c
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/pass.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 obj
    32  
    33  // Code and data passes.
    34  
    35  // brloop returns the ultimate destination of the series of unconditional jumps beginning at p.
    36  // In the case of an infinite loop, brloop returns nil.
    37  func brloop(p *Prog) *Prog {
    38  	c := 0
    39  	for q := p; q != nil; q = q.To.Target() {
    40  		if q.As != AJMP || q.To.Target() == nil {
    41  			return q
    42  		}
    43  		c++
    44  		if c >= 5000 {
    45  			// infinite loop
    46  			return nil
    47  		}
    48  	}
    49  	panic("unreachable")
    50  }
    51  
    52  // checkaddr checks that a has an expected encoding, especially TYPE_CONST vs TYPE_ADDR.
    53  func checkaddr(ctxt *Link, p *Prog, a *Addr) {
    54  	switch a.Type {
    55  	case TYPE_NONE, TYPE_REGREG2, TYPE_REGLIST:
    56  		return
    57  
    58  	case TYPE_BRANCH, TYPE_TEXTSIZE:
    59  		if a.Reg != 0 || a.Index != 0 || a.Scale != 0 || a.Name != 0 {
    60  			break
    61  		}
    62  		return
    63  
    64  	case TYPE_MEM:
    65  		return
    66  
    67  	case TYPE_CONST:
    68  		// TODO(rsc): After fixing SHRQ, check a.Index != 0 too.
    69  		if a.Name != 0 || a.Sym != nil || a.Reg != 0 {
    70  			ctxt.Diag("argument is TYPE_CONST, should be TYPE_ADDR, in %v", p)
    71  			return
    72  		}
    73  
    74  		if a.Reg != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.Val != nil {
    75  			break
    76  		}
    77  		return
    78  
    79  	case TYPE_FCONST, TYPE_SCONST:
    80  		if a.Reg != 0 || a.Index != 0 || a.Scale != 0 || a.Name != 0 || a.Offset != 0 || a.Sym != nil {
    81  			break
    82  		}
    83  		return
    84  
    85  	case TYPE_REG:
    86  		// TODO(rsc): After fixing PINSRQ, check a.Offset != 0 too.
    87  		// TODO(rsc): After fixing SHRQ, check a.Index != 0 too.
    88  		if a.Scale != 0 || a.Name != 0 || a.Sym != nil {
    89  			break
    90  		}
    91  		return
    92  
    93  	case TYPE_ADDR:
    94  		if a.Val != nil {
    95  			break
    96  		}
    97  		if a.Reg == 0 && a.Index == 0 && a.Scale == 0 && a.Name == 0 && a.Sym == nil {
    98  			ctxt.Diag("argument is TYPE_ADDR, should be TYPE_CONST, in %v", p)
    99  		}
   100  		return
   101  
   102  	case TYPE_SHIFT, TYPE_REGREG:
   103  		if a.Index != 0 || a.Scale != 0 || a.Name != 0 || a.Sym != nil || a.Val != nil {
   104  			break
   105  		}
   106  		return
   107  
   108  	case TYPE_INDIR:
   109  		// Expect sym and name to be set, nothing else.
   110  		// Technically more is allowed, but this is only used for *name(SB).
   111  		if a.Reg != 0 || a.Index != 0 || a.Scale != 0 || a.Name == 0 || a.Offset != 0 || a.Sym == nil || a.Val != nil {
   112  			break
   113  		}
   114  		return
   115  	case TYPE_SPECIAL:
   116  		if a.Reg != 0 || a.Index != 0 || a.Scale != 0 || a.Name != 0 || a.Class != 0 || a.Sym != nil {
   117  			break
   118  		}
   119  		return
   120  	}
   121  
   122  	ctxt.Diag("invalid encoding for argument %v", p)
   123  }
   124  
   125  func linkpatch(ctxt *Link, sym *LSym, newprog ProgAlloc) {
   126  	for p := sym.Func().Text; p != nil; p = p.Link {
   127  		checkaddr(ctxt, p, &p.From)
   128  		for _, v := range p.RestArgs {
   129  			checkaddr(ctxt, p, &v.Addr)
   130  		}
   131  		checkaddr(ctxt, p, &p.To)
   132  
   133  		if ctxt.Arch.Progedit != nil {
   134  			ctxt.Arch.Progedit(ctxt, p, newprog)
   135  		}
   136  		if p.To.Type != TYPE_BRANCH {
   137  			continue
   138  		}
   139  		if p.To.Val != nil {
   140  			continue
   141  		}
   142  
   143  		if p.To.Sym != nil {
   144  			continue
   145  		}
   146  		q := sym.Func().Text
   147  		for q != nil && p.To.Offset != q.Pc {
   148  			if q.Forwd != nil && p.To.Offset >= q.Forwd.Pc {
   149  				q = q.Forwd
   150  			} else {
   151  				q = q.Link
   152  			}
   153  		}
   154  
   155  		if q == nil {
   156  			name := "<nil>"
   157  			if p.To.Sym != nil {
   158  				name = p.To.Sym.Name
   159  			}
   160  			ctxt.Diag("branch out of range (%#x)\n%v [%s]", uint32(p.To.Offset), p, name)
   161  			p.To.Type = TYPE_NONE
   162  		}
   163  
   164  		p.To.SetTarget(q)
   165  	}
   166  
   167  	if !ctxt.Flag_optimize {
   168  		return
   169  	}
   170  
   171  	// Collapse series of jumps to jumps.
   172  	for p := sym.Func().Text; p != nil; p = p.Link {
   173  		if p.To.Target() == nil {
   174  			continue
   175  		}
   176  		p.To.SetTarget(brloop(p.To.Target()))
   177  		if p.To.Target() != nil && p.To.Type == TYPE_BRANCH {
   178  			p.To.Offset = p.To.Target().Pc
   179  		}
   180  	}
   181  }
   182
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