1 /* sframe-opt.c - optimize FRE and FDE information in SFrame.
2 Copyright (C) 2022-2023 Free Software Foundation, Inc.
3
4 This file is part of GAS, the GNU Assembler.
5
6 GAS is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 GAS is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GAS; see the file COPYING. If not, write to the Free
18 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
19 02110-1301, USA. */
20
21 #include "as.h"
22 #include "sframe.h"
23
24 /* The function estimates the size of a rs_sframe variant frag based on
25 the current values of the symbols. It is called before the
26 relaxation loop. We set fr_subtype{0:2} to the expected length. */
27
28 int
29 sframe_estimate_size_before_relax (fragS *frag)
30 {
31 offsetT width;
32 expressionS *exp;
33 symbolS *widthS;
34 int ret;
35
36 /* We are dealing with two different kind of fragments here which need
37 to be fixed up:
38 - first, FRE start address in each FRE, and
39 - second, Function info in each FDE (function info stores the FRE type)
40 The two kind of fragments can be differentiated based on the opcode
41 of the symbol. */
42 exp = symbol_get_value_expression (frag->fr_symbol);
43 gas_assert ((exp->X_op == O_modulus) || (exp->X_op == O_absent));
44 /* Fragment for function info in an SFrame FDE will always write
45 only one byte. */
46 if (exp->X_op == O_modulus)
47 ret = 1;
48 /* Fragment for the start address in an SFrame FRE may write out
49 1/2/4 bytes depending on the value of the diff. */
50 else
51 {
52 /* Get the width expression from the symbol. */
53 widthS = exp->X_op_symbol;
54 width = resolve_symbol_value (widthS);
55
56 if (width < (offsetT) SFRAME_FRE_TYPE_ADDR1_LIMIT)
57 ret = 1;
58 else if (width < (offsetT) SFRAME_FRE_TYPE_ADDR2_LIMIT)
59 ret = 2;
60 else
61 ret = 4;
62 }
63
64 frag->fr_subtype = (frag->fr_subtype & ~7) | (ret & 7);
65
66 return ret;
67 }
68
69 /* This function relaxes a rs_sframe variant frag based on the current
70 values of the symbols. fr_subtype{0:2} is the current length of
71 the frag. This returns the change in frag length. */
72
73 int
74 sframe_relax_frag (fragS *frag)
75 {
76 int oldsize, newsize;
77
78 oldsize = frag->fr_subtype & 7;
79 if (oldsize == 7)
80 oldsize = -1;
81 newsize = sframe_estimate_size_before_relax (frag);
82 return newsize - oldsize;
83 }
84
85 /* This function converts a rs_sframe variant frag into a normal fill
86 frag. This is called after all relaxation has been done.
87 fr_subtype{0:2} will be the desired length of the frag. */
88
89 void
90 sframe_convert_frag (fragS *frag)
91 {
92 offsetT fsize;
93 offsetT diff;
94 offsetT value;
95
96 offsetT rest_of_data;
97 uint8_t fde_type, fre_type;
98 uint8_t pauth_key;
99
100 expressionS *exp;
101 symbolS *dataS;
102 symbolS *fsizeS, *diffS;
103
104 /* We are dealing with two different kind of fragments here which need
105 to be fixed up:
106 - first, FRE start address in each FRE, and
107 - second, Function info in each FDE (function info stores the FRE type)
108 The two kind of fragments can be differentiated based on the opcode
109 of the symbol. */
110 exp = symbol_get_value_expression (frag->fr_symbol);
111 gas_assert ((exp->X_op == O_modulus) || (exp->X_op == O_absent));
112 /* Fragment for function info in an SFrame FDE. */
113 if (exp->X_op == O_modulus)
114 {
115 /* Gather the existing value of the rest of the data except
116 the fre_type. */
117 dataS = exp->X_add_symbol;
118 rest_of_data = (symbol_get_value_expression(dataS))->X_add_number;
119 fde_type = SFRAME_V1_FUNC_FDE_TYPE (rest_of_data);
120 pauth_key = SFRAME_V1_FUNC_PAUTH_KEY (rest_of_data);
121 gas_assert (fde_type == SFRAME_FDE_TYPE_PCINC);
122
123 /* Calculate the applicable fre_type. */
124 fsizeS = exp->X_op_symbol;
125 fsize = resolve_symbol_value (fsizeS);
126 if (fsize < (offsetT) SFRAME_FRE_TYPE_ADDR1_LIMIT)
127 fre_type = SFRAME_FRE_TYPE_ADDR1;
128 else if (fsize < (offsetT) SFRAME_FRE_TYPE_ADDR2_LIMIT)
129 fre_type = SFRAME_FRE_TYPE_ADDR2;
130 else
131 fre_type = SFRAME_FRE_TYPE_ADDR4;
132
133 /* Create the new function info. */
134 value = SFRAME_V1_FUNC_INFO (fde_type, fre_type);
135 value = SFRAME_V1_FUNC_INFO_UPDATE_PAUTH_KEY (pauth_key, value);
136
137 frag->fr_literal[frag->fr_fix] = value;
138 }
139 /* Fragment for the start address in an SFrame FRE. */
140 else
141 {
142 /* Get the fsize expression from the symbol. */
143 fsizeS = exp->X_op_symbol;
144 fsize = resolve_symbol_value (fsizeS);
145 /* Get the diff expression from the symbol. */
146 diffS= exp->X_add_symbol;
147 diff = resolve_symbol_value (diffS);
148 value = diff;
149
150 switch (frag->fr_subtype & 7)
151 {
152 case 1:
153 gas_assert (fsize < (offsetT) SFRAME_FRE_TYPE_ADDR1_LIMIT);
154 frag->fr_literal[frag->fr_fix] = diff;
155 break;
156 case 2:
157 gas_assert (fsize < (offsetT) SFRAME_FRE_TYPE_ADDR2_LIMIT);
158 md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 2);
159 break;
160 case 4:
161 md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 4);
162 break;
163 default:
164 abort ();
165 }
166 }
167
168 frag->fr_fix += frag->fr_subtype & 7;
169 frag->fr_type = rs_fill;
170 frag->fr_subtype = 0;
171 frag->fr_offset = 0;
172 /* FIXME do this now because we have evaluated and fixed up the fragments
173 manually ? */
174 frag->fr_symbol = 0;
175 }