1# Insert GAS CFI directives ("control frame information") into x86-64 asm input
2
3BEGIN {
4  # don't put CFI data in the .eh_frame ELF section (which we don't keep)
5  print ".cfi_sections .debug_frame"
6
7  # only emit CFI directives inside a function
8  in_function = 0
9
10  # emit .loc directives with line numbers from original source
11  printf ".file 1 \"%s\"\n", ARGV[1]
12  line_number = 0
13
14  # used to detect "call label; label:" trick
15  called = ""
16}
17
18function get_const1() {
19  # for instructions with 2 operands, get 1st operand (assuming it is constant)
20  match($0, /-?(0x[0-9a-fA-F]+|[0-9]+),/)
21  return parse_const(substr($0, RSTART, RLENGTH-1))
22}
23
24function canonicalize_reg(register) {
25  if (match(register, /^r/))
26    return register
27  else if (match(register, /^e/))
28    return "r" substr(register, 2, length(register)-1)
29  else if (match(register, /[hl]$/)) # AH, AL, BH, BL, etc
30    return "r" substr(register, 1, 1) "x"
31  else # AX, BX, CX, etc
32    return "r" register
33}
34function get_reg() {
35  # only use if you already know there is 1 and only 1 register
36  match($0, /%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/)
37  return canonicalize_reg(substr($0, RSTART+1, RLENGTH-1))
38}
39function get_reg1() {
40  # for instructions with 2 operands, get 1st operand (assuming it is register)
41  match($0, /%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15),/)
42  return canonicalize_reg(substr($0, RSTART+1, RLENGTH-2))
43}
44function get_reg2() {
45  # for instructions with 2 operands, get 2nd operand (assuming it is register)
46  match($0, /,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/)
47  return canonicalize_reg(substr($0, RSTART+2, RLENGTH-2))
48}
49
50function adjust_sp_offset(delta) {
51  if (in_function)
52    printf ".cfi_adjust_cfa_offset %d\n", delta
53}
54
55{
56  line_number = line_number + 1
57
58  # clean the input up before doing anything else
59  # delete comments
60  gsub(/(#|\/\/).*/, "")
61
62  # canonicalize whitespace
63  gsub(/[ \t]+/, " ") # mawk doesn't understand \s
64  gsub(/ *, */, ",")
65  gsub(/ *: */, ": ")
66  gsub(/ $/, "")
67  gsub(/^ /, "")
68}
69
70# check for assembler directives which we care about
71/^\.(section|data|text)/ {
72  # a .cfi_startproc/.cfi_endproc pair should be within the same section
73  # otherwise, clang will choke when generating ELF output
74  if (in_function) {
75    print ".cfi_endproc"
76    in_function = 0
77  }
78}
79/^\.type [a-zA-Z0-9_]+,\@function/ {
80  functions[substr($2, 1, length($2)-10)] = 1
81}
82# not interested in assembler directives beyond this, just pass them through
83/^\./ {
84  print
85  next
86}
87
88/^[a-zA-Z0-9_]+:/ {
89  label = substr($1, 1, length($1)-1) # drop trailing :
90
91  if (called == label) {
92    # note adjustment of stack pointer from "call label; label:"
93    adjust_sp_offset(8)
94  }
95
96  if (functions[label]) {
97    if (in_function)
98      print ".cfi_endproc"
99
100    in_function = 1
101    print ".cfi_startproc"
102
103    for (register in saved)
104      delete saved[register]
105    for (register in dirty)
106      delete dirty[register]
107  }
108
109  # an instruction may follow on the same line, so continue processing
110}
111
112/^$/ { next }
113
114{
115  called = ""
116  printf ".loc 1 %d\n", line_number
117  print
118}
119
120# KEEPING UP WITH THE STACK POINTER
121# %rsp should only be adjusted by pushing/popping or adding/subtracting constants
122#
123/pushl?/ {
124  adjust_sp_offset(8)
125}
126/popl?/ {
127  adjust_sp_offset(-8)
128}
129/addl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%rsp/ { adjust_sp_offset(-get_const1()) }
130/subl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%rsp/ { adjust_sp_offset(get_const1()) }
131
132/call/ {
133  if (match($0, /call [0-9]+f/)) # "forward" label
134    called = substr($0, RSTART+5, RLENGTH-6)
135  else if (match($0, /call [0-9a-zA-Z_]+/))
136    called = substr($0, RSTART+5, RLENGTH-5)
137}
138
139# TRACKING REGISTER VALUES FROM THE PREVIOUS STACK FRAME
140#
141/pushl? %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15)/ { # don't match "push (%reg)"
142  # if a register is being pushed, and its value has not changed since the
143  #   beginning of this function, the pushed value can be used when printing
144  #   local variables at the next level up the stack
145  # emit '.cfi_rel_offset' for that
146
147  if (in_function) {
148    register = get_reg()
149    if (!saved[register] && !dirty[register]) {
150      printf ".cfi_rel_offset %s,0\n", register
151      saved[register] = 1
152    }
153  }
154}
155
156/movl? %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15),-?(0x[0-9a-fA-F]+|[0-9]+)?\(%rsp\)/ {
157  if (in_function) {
158    register = get_reg()
159    if (match($0, /-?(0x[0-9a-fA-F]+|[0-9]+)\(%rsp\)/)) {
160      offset = parse_const(substr($0, RSTART, RLENGTH-6))
161    } else {
162      offset = 0
163    }
164    if (!saved[register] && !dirty[register]) {
165      printf ".cfi_rel_offset %s,%d\n", register, offset
166      saved[register] = 1
167    }
168  }
169}
170
171# IF REGISTER VALUES ARE UNCEREMONIOUSLY TRASHED
172# ...then we want to know about it.
173#
174function trashed(register) {
175  if (in_function && !saved[register] && !dirty[register]) {
176    printf ".cfi_undefined %s\n", register
177  }
178  dirty[register] = 1
179}
180# this does NOT exhaustively check for all possible instructions which could
181# overwrite a register value inherited from the caller (just the common ones)
182/mov.*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ { trashed(get_reg2()) }
183/(add|addl|sub|subl|and|or|xor|lea|sal|sar|shl|shr).*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ {
184  trashed(get_reg2())
185}
186/^i?mul [^,]*$/ { trashed("rax"); trashed("rdx") }
187/^i?mul.*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ { trashed(get_reg2()) }
188/^i?div/ { trashed("rax"); trashed("rdx") }
189
190/(dec|inc|not|neg|pop) %[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/  { trashed(get_reg()) }
191/cpuid/ { trashed("rax"); trashed("rbx"); trashed("rcx"); trashed("rdx") }
192
193END {
194  if (in_function)
195    print ".cfi_endproc"
196}
197