/* ehopt.c--optimize gcc exception frame information.
- Copyright (C) 1998 Free Software Foundation, Inc.
+ Copyright (C) 1998-2023 Free Software Foundation, Inc.
Written by Ian Lance Taylor <ian@cygnus.com>.
-This file is part of GAS, the GNU Assembler.
+ 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 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.
+ 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. */
+ 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"
ELF, since the exception frame information is always in a format
derived from DWARF. */
-#include "elf/dwarf2.h"
+#include "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:
+ .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)
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));
+struct cie_info
+{
+ unsigned code_alignment;
+ int z_augmentation;
+};
+
+static int get_cie_info (struct cie_info *);
-/* Get the code alignment factor from the CIE. */
+/* Extract information from the CIE. */
static int
-eh_frame_code_alignment ()
+get_cie_info (struct cie_info *info)
{
- static int code_alignment;
- segT current_seg;
- subsegT current_subseg;
fragS *f;
fixS *fix;
- int offset;
+ unsigned int offset;
+ char CIE_id;
char augmentation[10];
int iaug;
+ int code_alignment = 0;
- if (code_alignment != 0)
- return code_alignment;
+ /* We should find the CIE at the start of the section. */
- /* 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. */
+ /* First make sure that the CIE Identifier Tag is 0/-1. */
+
+ if (startswith (segment_name (now_seg), ".debug_frame"))
+ CIE_id = (char)0xff;
+ else
+ CIE_id = 0;
offset = 4;
while (f != NULL && offset >= f->fr_fix)
}
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;
- }
+ || 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. */
if (f == NULL
|| f->fr_fix - offset < 1
|| f->fr_literal[offset] != 1)
- {
- code_alignment = -1;
- return -1;
- }
+ return 0;
/* Skip the augmentation (a null terminated string). */
f = f->fr_next;
}
if (f == NULL)
- {
- code_alignment = -1;
- return -1;
- }
+ return 0;
+
while (offset < f->fr_fix && f->fr_literal[offset] != '\0')
{
if ((size_t) iaug < (sizeof augmentation) - 1)
f = f->fr_next;
}
if (f == NULL)
- {
- code_alignment = -1;
- return -1;
- }
+ return 0;
augmentation[iaug] = '\0';
if (augmentation[0] == '\0')
f = f->fr_next;
}
if (f == NULL)
- {
- code_alignment = -1;
- return -1;
- }
- }
- else
- {
- code_alignment = -1;
- return -1;
+ 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)
- {
- code_alignment = -1;
- return -1;
- }
+ if ((code_alignment & 0x80) != 0)
+ code_alignment = 0;
+
+ info->code_alignment = code_alignment;
+ info->z_augmentation = (augmentation[0] == 'z');
- return code_alignment;
+ 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.
change *EXP and *PNBYTES. */
int
-check_eh_frame (exp, pnbytes)
- expressionS *exp;
- unsigned int *pnbytes;
+check_eh_frame (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))
+ 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 (startswith (segment_name (now_seg), ".eh_frame")
+ && segment_name (now_seg)[9] != '_')
+ d = &eh_frame_data;
+ else if (startswith (segment_name (now_seg), ".debug_frame"))
+ 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. */
- saw_size = 0;
- saw_advance_loc4 = 0;
+ d->state = state_idle;
}
- if (flag_traditional_format)
+ switch (d->state)
{
- /* 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))
+ case state_idle:
+ if (*pnbytes == 4)
{
- saw_size = 1;
- size_end_sym = exp->X_add_symbol;
+ /* 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;
+ }
}
- }
- 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)
+ 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)
{
- /* Don't optimize. */
+ d->state = state_seeing_aug_size;
+ d->aug_size = 0;
+ d->aug_shift = 0;
}
- else if (exp->X_add_number % ca == 0
- && exp->X_add_number / ca < 0x40)
+ 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)
{
- loc4_frag->fr_literal[loc4_fix]
- = DW_CFA_advance_loc | (exp->X_add_number / ca);
- /* No more bytes needed. */
- return 1;
+ d->aug_size = exp->X_add_number;
+ d->state = state_skipping_aug;
}
- else if (exp->X_add_number < 0x100)
+ else if (*pnbytes == 1 && exp->X_op == O_constant)
{
- loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc1;
- *pnbytes = 1;
+ 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 if (exp->X_add_number < 0x10000)
+ 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
{
- loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc2;
- *pnbytes = 2;
+ int left = (d->aug_size -= *pnbytes);
+ if (left == 0)
+ d->state = state_wait_loc4;
+ else if (left < 0)
+ d->state = state_error;
}
- }
- else if (saw_advance_loc4
- && *pnbytes == 4
- && exp->X_op == O_subtract)
- {
+ break;
- /* 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;
+ 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;
- frag_var (rs_cfa, 4, 0, 0, make_expr_symbol (exp),
- loc4_fix, (char *) loc4_frag);
+ 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 (symbol_symbolS (exp->X_add_symbol)
+ && symbol_constant_p (exp->X_op_symbol)
+ && S_GET_SEGMENT (exp->X_op_symbol) == absolute_section
+ && ((exp->X_op == O_divide
+ ? *symbol_X_add_number (exp->X_op_symbol)
+ : (offsetT) 1 << *symbol_X_add_number (exp->X_op_symbol))
+ == (offsetT) d->cie_info.code_alignment))
+ {
+ expressionS *symval;
+
+ symval = symbol_get_value_expression (exp->X_add_symbol);
+ if (symval->X_op == O_subtract)
+ {
+ /* 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 (symval),
+ d->loc4_fix, (char *) d->loc4_frag);
+ return 1;
+ }
+ }
+ }
+ break;
- return 1;
+ case state_error:
+ /* Just skipping everything. */
+ break;
}
- 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. */
+ relaxation loop. We set fr_subtype{0:2} to the expected length. */
int
-eh_frame_estimate_size_before_relax (frag)
- fragS *frag;
+eh_frame_estimate_size_before_relax (fragS *frag)
{
- int ca;
offsetT diff;
+ int ca = frag->fr_subtype >> 3;
int ret;
- ca = eh_frame_code_alignment ();
- diff = resolve_symbol_value (frag->fr_symbol, 0);
+ diff = resolve_symbol_value (frag->fr_symbol);
- if (ca < 0)
- ret = 4;
- else if (diff % ca == 0 && diff / ca < 0x40)
+ gas_assert (ca > 0);
+ diff /= ca;
+ if (diff == 0)
+ ret = -1;
+ else if (diff < 0x40)
ret = 0;
else if (diff < 0x100)
ret = 1;
else
ret = 4;
- frag->fr_subtype = ret;
+ frag->fr_subtype = (frag->fr_subtype & ~7) | (ret & 7);
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. */
+ 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 (frag)
- fragS *frag;
+eh_frame_relax_frag (fragS *frag)
{
int oldsize, newsize;
- oldsize = frag->fr_subtype;
+ oldsize = frag->fr_subtype & 7;
+ if (oldsize == 7)
+ oldsize = -1;
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. */
+ fr_subtype{0:2} will be the desired length of the frag. */
void
-eh_frame_convert_frag (frag)
- fragS *frag;
+eh_frame_convert_frag (fragS *frag)
{
offsetT diff;
fragS *loc4_frag;
- int loc4_fix;
+ int loc4_fix, ca;
loc4_frag = (fragS *) frag->fr_opcode;
loc4_fix = (int) frag->fr_offset;
- diff = resolve_symbol_value (frag->fr_symbol, 1);
+ diff = resolve_symbol_value (frag->fr_symbol);
- if (frag->fr_subtype == 0)
+ ca = frag->fr_subtype >> 3;
+ gas_assert (ca > 0);
+ diff /= ca;
+ switch (frag->fr_subtype & 7)
{
- int ca;
+ case 0:
+ gas_assert (diff < 0x40);
+ loc4_frag->fr_literal[loc4_fix] = DW_CFA_advance_loc | diff;
+ break;
- 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);
+ case 1:
+ gas_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);
+ 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;
+
+ case 4:
+ md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 4);
+ break;
+
+ case 7:
+ gas_assert (diff == 0);
+ frag->fr_fix -= 8;
+ break;
+
+ default:
+ abort ();
}
- else
- md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 4);
- frag->fr_fix += frag->fr_subtype;
+ frag->fr_fix += frag->fr_subtype & 7;
frag->fr_type = rs_fill;
+ frag->fr_subtype = 0;
frag->fr_offset = 0;
}
projects / thirdparty / binutils-gdb.git / blobdiff