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Diffstat (limited to 'binutils-2.24/gas/ehopt.c')
| -rw-r--r-- | binutils-2.24/gas/ehopt.c | 557 |
1 files changed, 0 insertions, 557 deletions
diff --git a/binutils-2.24/gas/ehopt.c b/binutils-2.24/gas/ehopt.c deleted file mode 100644 index 70e1a00f..00000000 --- a/binutils-2.24/gas/ehopt.c +++ /dev/null @@ -1,557 +0,0 @@ -/* ehopt.c--optimize gcc exception frame information. - Copyright 1998, 2000, 2001, 2003, 2005, 2007, 2008, 2009 - 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 3, 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, 51 Franklin Street - Fifth Floor, Boston, MA - 02110-1301, USA. */ - -#include "as.h" -#include "subsegs.h" -#include "struc-symbol.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 "dwarf2.h" - -/* Try to optimize gcc 2.8 exception frame information. - - Exception frame information is emitted for every function in the - .eh_frame or .debug_frame sections. Simple information for a function - with no exceptions looks like this: - -__FRAME_BEGIN__: - .4byte .LLCIE1 / Length of Common Information Entry -.LSCIE1: -#if .eh_frame - .4byte 0x0 / CIE Identifier Tag -#elif .debug_frame - .4byte 0xffffffff / CIE Identifier Tag -#endif - .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. */ - -struct cie_info -{ - unsigned code_alignment; - int z_augmentation; -}; - -static int get_cie_info (struct cie_info *); - -/* Extract information from the CIE. */ - -static int -get_cie_info (struct cie_info *info) -{ - fragS *f; - fixS *fix; - int offset; - char CIE_id; - char augmentation[10]; - int iaug; - int code_alignment = 0; - - /* We should find the CIE at the start of the section. */ - - f = seg_info (now_seg)->frchainP->frch_root; - fix = seg_info (now_seg)->frchainP->fix_root; - - /* Look through the frags of the section to find the code alignment. */ - - /* First make sure that the CIE Identifier Tag is 0/-1. */ - - if (strncmp (segment_name (now_seg), ".debug_frame", 12) == 0) - CIE_id = (char)0xff; - else - CIE_id = 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] != CIE_id - || f->fr_literal[offset + 1] != CIE_id - || f->fr_literal[offset + 2] != CIE_id - || f->fr_literal[offset + 3] != CIE_id) - return 0; - - /* 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) - return 0; - - /* 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) - return 0; - - 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) - return 0; - - 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) - return 0; - } - else if (augmentation[0] != 'z') - return 0; - - /* 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; - - info->code_alignment = code_alignment; - info->z_augmentation = (augmentation[0] == 'z'); - - return 1; -} - -enum frame_state -{ - state_idle, - state_saw_size, - state_saw_cie_offset, - state_saw_pc_begin, - state_seeing_aug_size, - state_skipping_aug, - state_wait_loc4, - state_saw_loc4, - state_error, -}; - -/* 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 (expressionS *exp, unsigned int *pnbytes) -{ - struct frame_data - { - enum frame_state state; - - int cie_info_ok; - struct cie_info cie_info; - - symbolS *size_end_sym; - fragS *loc4_frag; - int loc4_fix; - - int aug_size; - int aug_shift; - }; - - static struct frame_data eh_frame_data; - static struct frame_data debug_frame_data; - struct frame_data *d; - - /* Don't optimize. */ - if (flag_traditional_format) - return 0; - -#ifdef md_allow_eh_opt - if (! md_allow_eh_opt) - return 0; -#endif - - /* Select the proper section data. */ - if (strncmp (segment_name (now_seg), ".eh_frame", 9) == 0 - && segment_name (now_seg)[9] != '_') - d = &eh_frame_data; - else if (strncmp (segment_name (now_seg), ".debug_frame", 12) == 0) - d = &debug_frame_data; - else - return 0; - - if (d->state >= state_saw_size && S_IS_DEFINED (d->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. */ - d->state = state_idle; - } - - switch (d->state) - { - case state_idle: - if (*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)) - { - d->state = state_saw_size; - d->size_end_sym = exp->X_add_symbol; - } - } - break; - - case state_saw_size: - case state_saw_cie_offset: - /* Assume whatever form it appears in, it appears atomically. */ - d->state = (enum frame_state) (d->state + 1); - break; - - case state_saw_pc_begin: - /* Decide whether we should see an augmentation. */ - if (! d->cie_info_ok - && ! (d->cie_info_ok = get_cie_info (&d->cie_info))) - d->state = state_error; - else if (d->cie_info.z_augmentation) - { - d->state = state_seeing_aug_size; - d->aug_size = 0; - d->aug_shift = 0; - } - else - d->state = state_wait_loc4; - break; - - case state_seeing_aug_size: - /* Bytes == -1 means this comes from an leb128 directive. */ - if ((int)*pnbytes == -1 && exp->X_op == O_constant) - { - d->aug_size = exp->X_add_number; - d->state = state_skipping_aug; - } - else if (*pnbytes == 1 && exp->X_op == O_constant) - { - unsigned char byte = exp->X_add_number; - d->aug_size |= (byte & 0x7f) << d->aug_shift; - d->aug_shift += 7; - if ((byte & 0x80) == 0) - d->state = state_skipping_aug; - } - else - d->state = state_error; - if (d->state == state_skipping_aug && d->aug_size == 0) - d->state = state_wait_loc4; - break; - - case state_skipping_aug: - if ((int)*pnbytes < 0) - d->state = state_error; - else - { - int left = (d->aug_size -= *pnbytes); - if (left == 0) - d->state = state_wait_loc4; - else if (left < 0) - d->state = state_error; - } - break; - - case state_wait_loc4: - if (*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. */ - frag_grow (1); - d->state = state_saw_loc4; - d->loc4_frag = frag_now; - d->loc4_fix = frag_now_fix (); - } - break; - - case state_saw_loc4: - d->state = state_wait_loc4; - if (*pnbytes != 4) - break; - if (exp->X_op == O_constant) - { - /* 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. */ - if (exp->X_add_number < 0x40) - { - d->loc4_frag->fr_literal[d->loc4_fix] - = DW_CFA_advance_loc | exp->X_add_number; - /* No more bytes needed. */ - return 1; - } - else if (exp->X_add_number < 0x100) - { - d->loc4_frag->fr_literal[d->loc4_fix] = DW_CFA_advance_loc1; - *pnbytes = 1; - } - else if (exp->X_add_number < 0x10000) - { - d->loc4_frag->fr_literal[d->loc4_fix] = DW_CFA_advance_loc2; - *pnbytes = 2; - } - } - else if (exp->X_op == O_subtract && d->cie_info.code_alignment == 1) - { - /* 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. */ - frag_var (rs_cfa, 4, 0, 1 << 3, make_expr_symbol (exp), - d->loc4_fix, (char *) d->loc4_frag); - return 1; - } - else if ((exp->X_op == O_divide - || exp->X_op == O_right_shift) - && d->cie_info.code_alignment > 1) - { - if (exp->X_add_symbol->bsym - && exp->X_op_symbol->bsym - && exp->X_add_symbol->sy_value.X_op == O_subtract - && exp->X_op_symbol->sy_value.X_op == O_constant - && ((exp->X_op == O_divide - ? exp->X_op_symbol->sy_value.X_add_number - : (offsetT) 1 << exp->X_op_symbol->sy_value.X_add_number) - == (offsetT) d->cie_info.code_alignment)) - { - /* This is a case we can optimize as well. 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. */ - frag_var (rs_cfa, 4, 0, d->cie_info.code_alignment << 3, - make_expr_symbol (&exp->X_add_symbol->sy_value), - d->loc4_fix, (char *) d->loc4_frag); - return 1; - } - } - break; - - case state_error: - /* Just skipping everything. */ - break; - } - - 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{0:2} to the expected length. */ - -int -eh_frame_estimate_size_before_relax (fragS *frag) -{ - offsetT diff; - int ca = frag->fr_subtype >> 3; - int ret; - - diff = resolve_symbol_value (frag->fr_symbol); - - gas_assert (ca > 0); - diff /= ca; - if (diff < 0x40) - ret = 0; - else if (diff < 0x100) - ret = 1; - else if (diff < 0x10000) - ret = 2; - else - ret = 4; - - frag->fr_subtype = (frag->fr_subtype & ~7) | ret; - - return ret; -} - -/* This function relaxes a rs_cfa variant frag based on the current - values of the symbols. fr_subtype{0:2} is the current length of - the frag. This returns the change in frag length. */ - -int -eh_frame_relax_frag (fragS *frag) -{ - int oldsize, newsize; - - oldsize = frag->fr_subtype & 7; - 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{0:2} will be the desired length of the frag. */ - -void -eh_frame_convert_frag (fragS *frag) -{ - offsetT diff; - fragS *loc4_frag; - int loc4_fix, ca; - - loc4_frag = (fragS *) frag->fr_opcode; - loc4_fix = (int) frag->fr_offset; - - diff = resolve_symbol_value (frag->fr_symbol); - - ca = frag->fr_subtype >> 3; - gas_assert (ca > 0); - diff /= ca; - switch (frag->fr_subtype & 7) - { - case 0: - gas_assert (diff < 0x40); - loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc | diff; - break; - - case 1: - gas_assert (diff < 0x100); - loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc1; - frag->fr_literal[frag->fr_fix] = diff; - break; - - case 2: - gas_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); - break; - - default: - md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 4); - break; - } - - frag->fr_fix += frag->fr_subtype & 7; - frag->fr_type = rs_fill; - frag->fr_subtype = 0; - frag->fr_offset = 0; -} |