pass.go raw
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 }
116
117 ctxt.Diag("invalid encoding for argument %v", p)
118 }
119
120 func linkpatch(ctxt *Link, sym *LSym, newprog ProgAlloc) {
121 for p := sym.Func.Text; p != nil; p = p.Link {
122 checkaddr(ctxt, p, &p.From)
123 if p.GetFrom3() != nil {
124 checkaddr(ctxt, p, p.GetFrom3())
125 }
126 checkaddr(ctxt, p, &p.To)
127
128 if ctxt.Arch.Progedit != nil {
129 ctxt.Arch.Progedit(ctxt, p, newprog)
130 }
131 if p.To.Type != TYPE_BRANCH {
132 continue
133 }
134 if p.To.Val != nil {
135 continue
136 }
137
138 if p.To.Sym != nil {
139 continue
140 }
141 q := sym.Func.Text
142 for q != nil && p.To.Offset != q.Pc {
143 if q.Forwd != nil && p.To.Offset >= q.Forwd.Pc {
144 q = q.Forwd
145 } else {
146 q = q.Link
147 }
148 }
149
150 if q == nil {
151 name := "<nil>"
152 if p.To.Sym != nil {
153 name = p.To.Sym.Name
154 }
155 ctxt.Diag("branch out of range (%#x)\n%v [%s]", uint32(p.To.Offset), p, name)
156 p.To.Type = TYPE_NONE
157 }
158
159 p.To.SetTarget(q)
160 }
161
162 if !ctxt.Flag_optimize {
163 return
164 }
165
166 // Collapse series of jumps to jumps.
167 for p := sym.Func.Text; p != nil; p = p.Link {
168 if p.To.Target() == nil {
169 continue
170 }
171 p.To.SetTarget(brloop(p.To.Target()))
172 if p.To.Target() != nil && p.To.Type == TYPE_BRANCH {
173 p.To.Offset = p.To.Target().Pc
174 }
175 }
176 }
177