github.com/hbdrawn/golang@v0.0.0-20141214014649-6b835209aba2/src/liblink/pass.c (about)

     1  // Inferno utils/6l/pass.c
     2  // http://code.google.com/p/inferno-os/source/browse/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  // Code and data passes.
    32  
    33  #include <u.h>
    34  #include <libc.h>
    35  #include <bio.h>
    36  #include <link.h>
    37  
    38  Prog*
    39  brchain(Link *ctxt, Prog *p)
    40  {
    41  	int i;
    42  
    43  	for(i=0; i<20; i++) {
    44  		if(p == nil || p->as != ctxt->arch->AJMP || p->pcond == nil)
    45  			return p;
    46  		p = p->pcond;
    47  	}
    48  	return nil;
    49  }
    50  
    51  Prog*
    52  brloop(Link *ctxt, Prog *p)
    53  {
    54  	int c;
    55  	Prog *q;
    56  
    57  	c = 0;
    58  	for(q = p; q != nil; q = q->pcond) {
    59  		if(q->as != ctxt->arch->AJMP || q->pcond == nil)
    60  			break;
    61  		c++;
    62  		if(c >= 5000)
    63  			return nil;
    64  	}
    65  	return q;
    66  }
    67  
    68  void
    69  linkpatch(Link *ctxt, LSym *sym)
    70  {
    71  	int32 c;
    72  	Prog *p, *q;
    73  
    74  	ctxt->cursym = sym;
    75  	
    76  	for(p = sym->text; p != nil; p = p->link) {
    77  		if(ctxt->arch->progedit)
    78  			ctxt->arch->progedit(ctxt, p);
    79  		if(p->to.type != ctxt->arch->D_BRANCH)
    80  			continue;
    81  		if(p->to.u.branch != nil) {
    82  			// TODO: Remove to.u.branch in favor of p->pcond.
    83  			p->pcond = p->to.u.branch;
    84  			continue;
    85  		}
    86  		if(p->to.sym != nil)
    87  			continue;
    88  		c = p->to.offset;
    89  		for(q = sym->text; q != nil;) {
    90  			if(c == q->pc)
    91  				break;
    92  			if(q->forwd != nil && c >= q->forwd->pc)
    93  				q = q->forwd;
    94  			else
    95  				q = q->link;
    96  		}
    97  		if(q == nil) {
    98  			ctxt->diag("branch out of range (%#ux)\n%P [%s]",
    99  				c, p, p->to.sym ? p->to.sym->name : "<nil>");
   100  			p->to.type = ctxt->arch->D_NONE;
   101  		}
   102  		p->to.u.branch = q;
   103  		p->pcond = q;
   104  	}
   105  	
   106  	for(p = sym->text; p != nil; p = p->link) {
   107  		p->mark = 0;	/* initialization for follow */
   108  		if(p->pcond != nil) {
   109  			p->pcond = brloop(ctxt, p->pcond);
   110  			if(p->pcond != nil)
   111  			if(p->to.type == ctxt->arch->D_BRANCH)
   112  				p->to.offset = p->pcond->pc;
   113  		}
   114  	}
   115  }