1/* sframe-opt.c - optimize FRE and FDE information in SFrame.
2   Copyright (C) 2022-2024 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
28int
29sframe_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
73int
74sframe_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
89void
90sframe_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}
176