gas/sframe-opt.c

   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 }