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Diffstat (limited to 'gas/ehopt.c')
| -rw-r--r-- | gas/ehopt.c | 469 |
1 files changed, 0 insertions, 469 deletions
diff --git a/gas/ehopt.c b/gas/ehopt.c deleted file mode 100644 index a0a5f62f4d7..00000000000 --- a/gas/ehopt.c +++ /dev/null @@ -1,469 +0,0 @@ -/* ehopt.c--optimize gcc exception frame information. - Copyright (C) 1998 Free Software Foundation, Inc. - Written by Ian Lance Taylor <ian@cygnus.com>. - -This file is part of GAS, the GNU Assembler. - -GAS is free software; you can redistribute it and/or modify -it under the terms of the GNU General Public License as published by -the Free Software Foundation; either version 2, or (at your option) -any later version. - -GAS is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. - -You should have received a copy of the GNU General Public License -along with GAS; see the file COPYING. If not, write to the Free -Software Foundation, 59 Temple Place - Suite 330, Boston, MA -02111-1307, USA. */ - -#include "as.h" -#include "subsegs.h" - -/* We include this ELF file, even though we may not be assembling for - ELF, since the exception frame information is always in a format - derived from DWARF. */ - -#include "elf/dwarf2.h" - -/* Try to optimize gcc 2.8 exception frame information. - - Exception frame information is emitted for every function in the - .eh_frame section. Simple information for a function with no - exceptions looks like this: - -__FRAME_BEGIN__: - .4byte .LLCIE1 / Length of Common Information Entry -.LSCIE1: - .4byte 0x0 / CIE Identifier Tag - .byte 0x1 / CIE Version - .byte 0x0 / CIE Augmentation (none) - .byte 0x1 / ULEB128 0x1 (CIE Code Alignment Factor) - .byte 0x7c / SLEB128 -4 (CIE Data Alignment Factor) - .byte 0x8 / CIE RA Column - .byte 0xc / DW_CFA_def_cfa - .byte 0x4 / ULEB128 0x4 - .byte 0x4 / ULEB128 0x4 - .byte 0x88 / DW_CFA_offset, column 0x8 - .byte 0x1 / ULEB128 0x1 - .align 4 -.LECIE1: - .set .LLCIE1,.LECIE1-.LSCIE1 / CIE Length Symbol - .4byte .LLFDE1 / FDE Length -.LSFDE1: - .4byte .LSFDE1-__FRAME_BEGIN__ / FDE CIE offset - .4byte .LFB1 / FDE initial location - .4byte .LFE1-.LFB1 / FDE address range - .byte 0x4 / DW_CFA_advance_loc4 - .4byte .LCFI0-.LFB1 - .byte 0xe / DW_CFA_def_cfa_offset - .byte 0x8 / ULEB128 0x8 - .byte 0x85 / DW_CFA_offset, column 0x5 - .byte 0x2 / ULEB128 0x2 - .byte 0x4 / DW_CFA_advance_loc4 - .4byte .LCFI1-.LCFI0 - .byte 0xd / DW_CFA_def_cfa_register - .byte 0x5 / ULEB128 0x5 - .byte 0x4 / DW_CFA_advance_loc4 - .4byte .LCFI2-.LCFI1 - .byte 0x2e / DW_CFA_GNU_args_size - .byte 0x4 / ULEB128 0x4 - .byte 0x4 / DW_CFA_advance_loc4 - .4byte .LCFI3-.LCFI2 - .byte 0x2e / DW_CFA_GNU_args_size - .byte 0x0 / ULEB128 0x0 - .align 4 -.LEFDE1: - .set .LLFDE1,.LEFDE1-.LSFDE1 / FDE Length Symbol - - The immediate issue we can address in the assembler is the - DW_CFA_advance_loc4 followed by a four byte value. The value is - the difference of two addresses in the function. Since gcc does - not know this value, it always uses four bytes. We will know the - value at the end of assembly, so we can do better. */ - -static int eh_frame_code_alignment PARAMS ((void)); - -/* Get the code alignment factor from the CIE. */ - -static int -eh_frame_code_alignment () -{ - static int code_alignment; - segT current_seg; - subsegT current_subseg; - fragS *f; - fixS *fix; - int offset; - char augmentation[10]; - int iaug; - - if (code_alignment != 0) - return code_alignment; - - /* We should find the CIE at the start of the .eh_frame section. */ - - current_seg = now_seg; - current_subseg = now_subseg; - subseg_new (".eh_frame", 0); -#if defined (BFD_ASSEMBLER) || defined (MANY_SEGMENTS) - f = seg_info (now_seg)->frchainP->frch_root; -#else - f = frchain_now->frch_root; -#endif -#ifdef BFD_ASSEMBLER - fix = seg_info (now_seg)->frchainP->fix_root; -#else - fix = *seg_fix_rootP; -#endif - subseg_set (current_seg, current_subseg); - - /* Look through the frags of the section to find the code alignment. */ - - /* First make sure that the CIE Identifier Tag is 0. */ - - offset = 4; - while (f != NULL && offset >= f->fr_fix) - { - offset -= f->fr_fix; - f = f->fr_next; - } - if (f == NULL - || f->fr_fix - offset < 4 - || f->fr_literal[offset] != 0 - || f->fr_literal[offset + 1] != 0 - || f->fr_literal[offset + 2] != 0 - || f->fr_literal[offset + 3] != 0) - { - code_alignment = -1; - return -1; - } - - /* Next make sure the CIE version number is 1. */ - - offset += 4; - while (f != NULL && offset >= f->fr_fix) - { - offset -= f->fr_fix; - f = f->fr_next; - } - if (f == NULL - || f->fr_fix - offset < 1 - || f->fr_literal[offset] != 1) - { - code_alignment = -1; - return -1; - } - - /* Skip the augmentation (a null terminated string). */ - - iaug = 0; - ++offset; - while (1) - { - while (f != NULL && offset >= f->fr_fix) - { - offset -= f->fr_fix; - f = f->fr_next; - } - if (f == NULL) - { - code_alignment = -1; - return -1; - } - while (offset < f->fr_fix && f->fr_literal[offset] != '\0') - { - if ((size_t) iaug < (sizeof augmentation) - 1) - { - augmentation[iaug] = f->fr_literal[offset]; - ++iaug; - } - ++offset; - } - if (offset < f->fr_fix) - break; - } - ++offset; - while (f != NULL && offset >= f->fr_fix) - { - offset -= f->fr_fix; - f = f->fr_next; - } - if (f == NULL) - { - code_alignment = -1; - return -1; - } - - augmentation[iaug] = '\0'; - if (augmentation[0] == '\0') - { - /* No augmentation. */ - } - else if (strcmp (augmentation, "eh") == 0) - { - /* We have to skip a pointer. Unfortunately, we don't know how - large it is. We find out by looking for a matching fixup. */ - while (fix != NULL - && (fix->fx_frag != f || fix->fx_where != offset)) - fix = fix->fx_next; - if (fix == NULL) - offset += 4; - else - offset += fix->fx_size; - while (f != NULL && offset >= f->fr_fix) - { - offset -= f->fr_fix; - f = f->fr_next; - } - if (f == NULL) - { - code_alignment = -1; - return -1; - } - } - else - { - code_alignment = -1; - return -1; - } - - /* We're now at the code alignment factor, which is a ULEB128. If - it isn't a single byte, forget it. */ - - code_alignment = f->fr_literal[offset] & 0xff; - if ((code_alignment & 0x80) != 0 || code_alignment == 0) - { - code_alignment = -1; - return -1; - } - - return code_alignment; -} - -/* This function is called from emit_expr. It looks for cases which - we can optimize. - - Rather than try to parse all this information as we read it, we - look for a single byte DW_CFA_advance_loc4 followed by a 4 byte - difference. We turn that into a rs_cfa_advance frag, and handle - those frags at the end of the assembly. If the gcc output changes - somewhat, this optimization may stop working. - - This function returns non-zero if it handled the expression and - emit_expr should not do anything, or zero otherwise. It can also - change *EXP and *PNBYTES. */ - -int -check_eh_frame (exp, pnbytes) - expressionS *exp; - unsigned int *pnbytes; -{ - static int saw_size; - static symbolS *size_end_sym; - static int saw_advance_loc4; - static fragS *loc4_frag; - static int loc4_fix; - - if (saw_size - && S_IS_DEFINED (size_end_sym)) - { - /* We have come to the end of the CIE or FDE. See below where - we set saw_size. We must check this first because we may now - be looking at the next size. */ - saw_size = 0; - saw_advance_loc4 = 0; - } - - if (flag_traditional_format) - { - /* Don't optimize. */ - } - else if (strcmp (segment_name (now_seg), ".eh_frame") != 0) - { - saw_size = 0; - saw_advance_loc4 = 0; - } - else if (! saw_size - && *pnbytes == 4) - { - /* This might be the size of the CIE or FDE. We want to know - the size so that we don't accidentally optimize across an FDE - boundary. We recognize the size in one of two forms: a - symbol which will later be defined as a difference, or a - subtraction of two symbols. Either way, we can tell when we - are at the end of the FDE because the symbol becomes defined - (in the case of a subtraction, the end symbol, from which the - start symbol is being subtracted). Other ways of describing - the size will not be optimized. */ - if ((exp->X_op == O_symbol || exp->X_op == O_subtract) - && ! S_IS_DEFINED (exp->X_add_symbol)) - { - saw_size = 1; - size_end_sym = exp->X_add_symbol; - } - } - else if (saw_size - && *pnbytes == 1 - && exp->X_op == O_constant - && exp->X_add_number == DW_CFA_advance_loc4) - { - /* This might be a DW_CFA_advance_loc4. Record the frag and the - position within the frag, so that we can change it later. */ - saw_advance_loc4 = 1; - frag_grow (1); - loc4_frag = frag_now; - loc4_fix = frag_now_fix (); - } - else if (saw_advance_loc4 - && *pnbytes == 4 - && exp->X_op == O_constant) - { - int ca; - - /* This is a case which we can optimize. The two symbols being - subtracted were in the same frag and the expression was - reduced to a constant. We can do the optimization entirely - in this function. */ - - saw_advance_loc4 = 0; - - ca = eh_frame_code_alignment (); - if (ca < 0) - { - /* Don't optimize. */ - } - else if (exp->X_add_number % ca == 0 - && exp->X_add_number / ca < 0x40) - { - loc4_frag->fr_literal[loc4_fix] - = DW_CFA_advance_loc | (exp->X_add_number / ca); - /* No more bytes needed. */ - return 1; - } - else if (exp->X_add_number < 0x100) - { - loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc1; - *pnbytes = 1; - } - else if (exp->X_add_number < 0x10000) - { - loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc2; - *pnbytes = 2; - } - } - else if (saw_advance_loc4 - && *pnbytes == 4 - && exp->X_op == O_subtract) - { - - /* This is a case we can optimize. The expression was not - reduced, so we can not finish the optimization until the end - of the assembly. We set up a variant frag which we handle - later. */ - - saw_advance_loc4 = 0; - - frag_var (rs_cfa, 4, 0, 0, make_expr_symbol (exp), - loc4_fix, (char *) loc4_frag); - - return 1; - } - else - saw_advance_loc4 = 0; - - return 0; -} - -/* The function estimates the size of a rs_cfa variant frag based on - the current values of the symbols. It is called before the - relaxation loop. We set fr_subtype to the expected length. */ - -int -eh_frame_estimate_size_before_relax (frag) - fragS *frag; -{ - int ca; - offsetT diff; - int ret; - - ca = eh_frame_code_alignment (); - diff = resolve_symbol_value (frag->fr_symbol, 0); - - if (ca < 0) - ret = 4; - else if (diff % ca == 0 && diff / ca < 0x40) - ret = 0; - else if (diff < 0x100) - ret = 1; - else if (diff < 0x10000) - ret = 2; - else - ret = 4; - - frag->fr_subtype = ret; - - return ret; -} - -/* This function relaxes a rs_cfa variant frag based on the current - values of the symbols. fr_subtype is the current length of the - frag. This returns the change in frag length. */ - -int -eh_frame_relax_frag (frag) - fragS *frag; -{ - int oldsize, newsize; - - oldsize = frag->fr_subtype; - newsize = eh_frame_estimate_size_before_relax (frag); - return newsize - oldsize; -} - -/* This function converts a rs_cfa variant frag into a normal fill - frag. This is called after all relaxation has been done. - fr_subtype will be the desired length of the frag. */ - -void -eh_frame_convert_frag (frag) - fragS *frag; -{ - offsetT diff; - fragS *loc4_frag; - int loc4_fix; - - loc4_frag = (fragS *) frag->fr_opcode; - loc4_fix = (int) frag->fr_offset; - - diff = resolve_symbol_value (frag->fr_symbol, 1); - - if (frag->fr_subtype == 0) - { - int ca; - - ca = eh_frame_code_alignment (); - assert (ca > 0 && diff % ca == 0 && diff / ca < 0x40); - loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc | (diff / ca); - } - else if (frag->fr_subtype == 1) - { - assert (diff < 0x100); - loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc1; - frag->fr_literal[frag->fr_fix] = diff; - } - else if (frag->fr_subtype == 2) - { - assert (diff < 0x10000); - loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc2; - md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 2); - } - else - md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 4); - - frag->fr_fix += frag->fr_subtype; - frag->fr_type = rs_fill; - frag->fr_offset = 0; -} |