* Re: [asm] Difference of symbols in another section
2001-09-08 8:02 ` [asm] Difference of symbols in another section Harshad R Joglekar
@ 2001-09-09 6:56 ` Alan Modra
0 siblings, 0 replies; 4+ messages in thread
From: Alan Modra @ 2001-09-09 6:56 UTC (permalink / raw)
To: Harshad R Joglekar; +Cc: binutils
On Sat, Sep 08, 2001 at 08:36:28PM +0530, Harshad R Joglekar wrote:
>
> The assembler gives an error only when listings are enabled:
Ah, missed that.
> How about removing the check itself from expr.c (patch below)? This
> check is probably being done later when resolving symbols ??
I think we still want the check here, as otherwise we might lose the
line number information when reporting errors.
I'm going to commit the following, which should cure these problems (*),
and also extends allowed expressions a little.
* expr.c (expr): Move code setting "retval" to the end of the loop,
and rearrange for efficiency. For "PIC code" subtraction, use
"rightseg" rather than recalculating. For "symbol OP symbol"
subtract, set "retval" to absolute_section if symbols in same
section.
* symbols.c (resolve_symbol_value): Resolve "sym +/- expr" to an
O_symbol. Simplify a +/- b code. Allow equality and non-equality
comparisons on symbols from any section. Allow other comparison
operators as for subtraction.
(symbol_equated_reloc_p): New predicate function.
* symbols.h (symbol_equated_reloc_p): Declare.
* write.c (adjust_reloc_syms): Use symbol_equated_reloc_p.
(write_relocs): Likewise.
(write_object_file): Likewise.
(relax_segment <rs_machine_dependent>): Ensure segment for
expression syms is set correctly.
* config/tc-mips.c (md_estimate_size_before_relax): Likewise.
* config/tc-i386.c (md_assemble <Output jumps>): Don't lose part
of a complex expression when setting up frag_var.
*) At least on x86. There are other gas/config/tc-* files that should
be patched similarly to tc-i386.c for frag_var calls. hp has already
fixed cris, I see. ;)
--
Alan Modra
Index: gas/expr.c
===================================================================
RCS file: /cvs/src/src/gas/expr.c,v
retrieving revision 1.38
diff -u -p -r1.38 expr.c
--- expr.c 2001/08/14 20:00:32 1.38
+++ expr.c 2001/09/09 12:55:05
@@ -1699,21 +1699,6 @@ expr (rankarg, resultP)
}
}
- if (retval == undefined_section)
- {
- if (SEG_NORMAL (rightseg))
- retval = rightseg;
- }
- else if (! SEG_NORMAL (retval))
- retval = rightseg;
- else if (SEG_NORMAL (rightseg)
- && retval != rightseg
-#ifdef DIFF_EXPR_OK
- && op_left != O_subtract
-#endif
- )
- as_bad (_("operation combines symbols in different segments"));
-
op_right = operator (&op_chars);
know (op_right == O_illegal
@@ -1769,7 +1754,7 @@ expr (rankarg, resultP)
&& resultP->X_op == O_symbol
&& (symbol_get_frag (right.X_add_symbol)
== symbol_get_frag (resultP->X_add_symbol))
- && SEG_NORMAL (S_GET_SEGMENT (right.X_add_symbol)))
+ && SEG_NORMAL (rightseg))
{
resultP->X_add_number -= right.X_add_number;
@@ -1865,7 +1850,14 @@ expr (rankarg, resultP)
if (op_left == O_add)
resultP->X_add_number += right.X_add_number;
else if (op_left == O_subtract)
- resultP->X_add_number -= right.X_add_number;
+ {
+ resultP->X_add_number -= right.X_add_number;
+ if (retval == rightseg && SEG_NORMAL (retval))
+ {
+ retval = absolute_section;
+ rightseg = absolute_section;
+ }
+ }
}
else
{
@@ -1875,6 +1867,21 @@ expr (rankarg, resultP)
resultP->X_op = op_left;
resultP->X_add_number = 0;
resultP->X_unsigned = 1;
+ }
+
+ if (retval != rightseg)
+ {
+ if (! SEG_NORMAL (retval))
+ {
+ if (retval != undefined_section || SEG_NORMAL (rightseg))
+ retval = rightseg;
+ }
+ else if (SEG_NORMAL (rightseg)
+#ifdef DIFF_EXPR_OK
+ && op_left != O_subtract
+#endif
+ )
+ as_bad (_("operation combines symbols in different segments"));
}
op_left = op_right;
Index: gas/symbols.c
===================================================================
RCS file: /cvs/src/src/gas/symbols.c,v
retrieving revision 1.29
diff -u -p -r1.29 symbols.c
--- symbols.c 2001/08/09 14:42:07 1.29
+++ symbols.c 2001/09/09 12:55:07
@@ -914,8 +914,11 @@ resolve_symbol_value (symp)
case O_symbol:
case O_symbol_rva:
left = resolve_symbol_value (add_symbol);
- do_symbol:
+ seg_left = S_GET_SEGMENT (add_symbol);
+ if (finalize_syms)
+ symp->sy_value.X_op_symbol = NULL;
+ do_symbol:
if (symp->sy_mri_common)
{
/* This is a symbol inside an MRI common section. The
@@ -933,8 +936,8 @@ resolve_symbol_value (symp)
copy_symbol_attributes (symp, add_symbol);
}
- /* If we have equated this symbol to an undefined symbol, we
- keep X_op set to O_symbol, and we don't change
+ /* If we have equated this symbol to an undefined or common
+ symbol, keep X_op set to O_symbol, and don't change
X_add_number. This permits the routine which writes out
relocation to detect this case, and convert the
relocation to be against the symbol to which this symbol
@@ -943,21 +946,41 @@ resolve_symbol_value (symp)
{
if (finalize_syms)
{
- final_seg = S_GET_SEGMENT (add_symbol);
symp->sy_value.X_op = O_symbol;
symp->sy_value.X_add_symbol = add_symbol;
symp->sy_value.X_add_number = final_val;
+ /* Use X_op_symbol as a flag. */
+ symp->sy_value.X_op_symbol = add_symbol;
+ final_seg = seg_left;
}
final_val = 0;
resolved = symbol_resolved_p (add_symbol);
symp->sy_resolving = 0;
goto exit_dont_set_value;
}
+ else if (finalize_syms && final_seg == expr_section
+ && seg_left != expr_section)
+ {
+ /* If the symbol is an expression symbol, do similarly
+ as for undefined and common syms above. Handles
+ "sym +/- expr" where "expr" cannot be evaluated
+ immediately, and we want relocations to be against
+ "sym", eg. because it is weak. */
+ symp->sy_value.X_op = O_symbol;
+ symp->sy_value.X_add_symbol = add_symbol;
+ symp->sy_value.X_add_number = final_val;
+ symp->sy_value.X_op_symbol = add_symbol;
+ final_seg = seg_left;
+ final_val += symp->sy_frag->fr_address + left;
+ resolved = symbol_resolved_p (add_symbol);
+ symp->sy_resolving = 0;
+ goto exit_dont_set_value;
+ }
else
{
final_val += symp->sy_frag->fr_address + left;
if (final_seg == expr_section || final_seg == undefined_section)
- final_seg = S_GET_SEGMENT (add_symbol);
+ final_seg = seg_left;
}
resolved = symbol_resolved_p (add_symbol);
@@ -1008,42 +1031,49 @@ resolve_symbol_value (symp)
/* Simplify addition or subtraction of a constant by folding the
constant into X_add_number. */
- if (op == O_add || op == O_subtract)
+ if (op == O_add)
{
if (seg_right == absolute_section)
{
- if (op == O_add)
- final_val += right;
- else
- final_val -= right;
- op = O_symbol;
- op_symbol = NULL;
+ final_val += right;
goto do_symbol;
}
- else if (seg_left == absolute_section && op == O_add)
+ else if (seg_left == absolute_section)
{
- op = O_symbol;
final_val += left;
add_symbol = op_symbol;
left = right;
- op_symbol = NULL;
+ seg_left = seg_right;
+ goto do_symbol;
+ }
+ }
+ else if (op == O_subtract)
+ {
+ if (seg_right == absolute_section)
+ {
+ final_val -= right;
goto do_symbol;
}
}
+
+ /* Equality and non-equality tests are permitted on anything.
+ Subtraction, and other comparison operators are permitted if
+ both operands are in the same section. Otherwise, both
+ operands must be absolute. We already handled the case of
+ addition or subtraction of a constant above. This will
+ probably need to be changed for an object file format which
+ supports arbitrary expressions, such as IEEE-695.
- /* Subtraction is permitted if both operands are in the same
- section. Otherwise, both operands must be absolute. We
- already handled the case of addition or subtraction of a
- constant above. This will probably need to be changed
- for an object file format which supports arbitrary
- expressions, such as IEEE-695. */
- /* Don't emit messages unless we're finalizing the symbol value,
+ Don't emit messages unless we're finalizing the symbol value,
otherwise we may get the same message multiple times. */
- if ((seg_left != absolute_section
- || seg_right != absolute_section)
- && (op != O_subtract
+ if (op != O_eq && op != O_ne
+ && (seg_left != absolute_section
+ || seg_right != absolute_section)
+ && ((op != O_subtract
+ && op != O_lt && op != O_le && op != O_ge && op != O_gt)
|| seg_left != seg_right
- || seg_left == undefined_section)
+ || (seg_left == undefined_section
+ && add_symbol != op_symbol))
&& finalize_syms)
{
char *file;
@@ -1114,8 +1144,15 @@ resolve_symbol_value (symp)
case O_bit_and: left &= right; break;
case O_add: left += right; break;
case O_subtract: left -= right; break;
- case O_eq: left = left == right ? ~ (offsetT) 0 : 0; break;
- case O_ne: left = left != right ? ~ (offsetT) 0 : 0; break;
+ case O_eq:
+ case O_ne:
+ left = (left == right && seg_left == seg_right
+ && (seg_left != undefined_section
+ || add_symbol == op_symbol)
+ ? ~ (offsetT) 0 : 0);
+ if (symp->sy_value.X_op == O_ne)
+ left = ~left;
+ break;
case O_lt: left = left < right ? ~ (offsetT) 0 : 0; break;
case O_le: left = left <= right ? ~ (offsetT) 0 : 0; break;
case O_ge: left = left >= right ? ~ (offsetT) 0 : 0; break;
@@ -2144,6 +2181,24 @@ symbol_equated_p (s)
if (LOCAL_SYMBOL_CHECK (s))
return 0;
return s->sy_value.X_op == O_symbol;
+}
+
+/* Return whether a symbol is equated to another symbol, and should be
+ treated specially when writing out relocs. */
+
+int
+symbol_equated_reloc_p (s)
+ symbolS *s;
+{
+ if (LOCAL_SYMBOL_CHECK (s))
+ return 0;
+ /* X_op_symbol, normally not used for O_symbol, is set by
+ resolve_symbol_value to flag expression syms that have been
+ equated. */
+ return (s->sy_value.X_op == O_symbol
+ && ((s->sy_resolved && s->sy_value.X_op_symbol != NULL)
+ || ! S_IS_DEFINED (s)
+ || S_IS_COMMON (s)));
}
/* Return whether a symbol has a constant value. */
Index: gas/symbols.h
===================================================================
RCS file: /cvs/src/src/gas/symbols.h,v
retrieving revision 1.6
diff -u -p -r1.6 symbols.h
--- symbols.h 2001/05/22 10:23:48 1.6
+++ symbols.h 2001/09/09 12:55:07
@@ -185,6 +185,7 @@ extern void symbol_mark_resolved PARAMS
extern int symbol_resolved_p PARAMS ((symbolS *));
extern int symbol_section_p PARAMS ((symbolS *));
extern int symbol_equated_p PARAMS ((symbolS *));
+extern int symbol_equated_reloc_p PARAMS ((symbolS *));
extern int symbol_constant_p PARAMS ((symbolS *));
#ifdef BFD_ASSEMBLER
Index: gas/write.c
===================================================================
RCS file: /cvs/src/src/gas/write.c,v
retrieving revision 1.44
diff -u -p -r1.44 write.c
--- write.c 2001/08/01 01:44:25 1.44
+++ write.c 2001/09/09 12:55:09
@@ -769,8 +769,7 @@ adjust_reloc_syms (abfd, sec, xxx)
/* If this symbol is equated to an undefined symbol, convert
the fixup to being against that symbol. */
- if (sym != NULL && symbol_equated_p (sym)
- && (! S_IS_DEFINED (sym) || S_IS_COMMON (sym)))
+ if (sym != NULL && symbol_equated_reloc_p (sym))
{
fixp->fx_offset += symbol_get_value_expression (sym)->X_add_number;
sym = symbol_get_value_expression (sym)->X_add_symbol;
@@ -983,11 +982,10 @@ write_relocs (abfd, sec, xxx)
}
/* If this is an undefined symbol which was equated to another
- symbol, then use generate the reloc against the latter symbol
+ symbol, then generate the reloc against the latter symbol
rather than the former. */
sym = fixp->fx_addsy;
- while (symbol_equated_p (sym)
- && (! S_IS_DEFINED (sym) || S_IS_COMMON (sym)))
+ while (symbol_equated_reloc_p (sym))
{
symbolS *n;
@@ -1059,8 +1057,7 @@ write_relocs (abfd, sec, xxx)
symbol, then generate the reloc against the latter symbol
rather than the former. */
sym = fixp->fx_addsy;
- while (symbol_equated_p (sym)
- && (! S_IS_DEFINED (sym) || S_IS_COMMON (sym)))
+ while (symbol_equated_reloc_p (sym))
sym = symbol_get_value_expression (sym)->X_add_symbol;
fixp->fx_addsy = sym;
@@ -1960,8 +1957,7 @@ write_object_file ()
/* Skip symbols which were equated to undefined or common
symbols. */
- if (symbol_equated_p (symp)
- && (! S_IS_DEFINED (symp) || S_IS_COMMON (symp)))
+ if (symbol_equated_reloc_p (symp))
{
symbol_remove (symp, &symbol_rootP, &symbol_lastP);
continue;
@@ -2264,6 +2260,12 @@ relax_segment (segment_frag_root, segmen
break;
case rs_machine_dependent:
+ /* If fr_symbol is an expression, this call to
+ resolve_symbol_value sets up the correct segment, which will
+ likely be needed in md_estimate_size_before_relax. */
+ if (fragP->fr_symbol)
+ resolve_symbol_value (fragP->fr_symbol);
+
address += md_estimate_size_before_relax (fragP, segment);
break;
Index: gas/config/tc-mips.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-mips.c,v
retrieving revision 1.73
diff -u -p -r1.73 tc-mips.c
--- tc-mips.c 2001/09/07 05:54:11 1.73
+++ tc-mips.c 2001/09/09 12:55:38
@@ -11143,8 +11143,7 @@ md_estimate_size_before_relax (fragp, se
sym = fragp->fr_symbol;
/* Handle the case of a symbol equated to another symbol. */
- while (symbol_equated_p (sym)
- && (! S_IS_DEFINED (sym) || S_IS_COMMON (sym)))
+ while (symbol_equated_reloc_p (sym))
{
symbolS *n;
Index: gas/config/tc-i386.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-i386.c,v
retrieving revision 1.102
diff -u -p -r1.102 tc-i386.c
--- tc-i386.c 2001/08/01 02:27:11 1.102
+++ tc-i386.c 2001/09/09 12:55:28
@@ -2741,6 +2741,9 @@ md_assemble (line)
{
int code16;
int prefix;
+ relax_substateT subtype;
+ symbolS *sym;
+ offsetT off;
code16 = 0;
if (flag_code == CODE_16BIT)
@@ -2785,19 +2788,29 @@ md_assemble (line)
if (i.prefix[REX_PREFIX])
*p++ = i.prefix[REX_PREFIX];
*p = i.tm.base_opcode;
- /* 1 possible extra opcode + displacement go in var part.
+
+ if ((unsigned char) *p == JUMP_PC_RELATIVE)
+ subtype = ENCODE_RELAX_STATE (UNCOND_JUMP, SMALL);
+ else if ((cpu_arch_flags & Cpu386) != 0)
+ subtype = ENCODE_RELAX_STATE (COND_JUMP, SMALL);
+ else
+ subtype = ENCODE_RELAX_STATE (COND_JUMP86, SMALL);
+ subtype |= code16;
+
+ sym = i.op[0].disps->X_add_symbol;
+ off = i.op[0].disps->X_add_number;
+
+ if (i.op[0].disps->X_op != O_constant
+ && i.op[0].disps->X_op != O_symbol)
+ {
+ /* Handle complex expressions. */
+ sym = make_expr_symbol (i.op[0].disps);
+ off = 0;
+ }
+
+ /* 1 possible extra opcode + 4 byte displacement go in var part.
Pass reloc in fr_var. */
- frag_var (rs_machine_dependent,
- 1 + 4,
- i.reloc[0],
- ((unsigned char) *p == JUMP_PC_RELATIVE
- ? ENCODE_RELAX_STATE (UNCOND_JUMP, SMALL) | code16
- : ((cpu_arch_flags & Cpu386) != 0
- ? ENCODE_RELAX_STATE (COND_JUMP, SMALL) | code16
- : ENCODE_RELAX_STATE (COND_JUMP86, SMALL) | code16)),
- i.op[0].disps->X_add_symbol,
- i.op[0].disps->X_add_number,
- p);
+ frag_var (rs_machine_dependent, 5, i.reloc[0], subtype, sym, off, p);
}
else if (i.tm.opcode_modifier & (JumpByte | JumpDword))
{
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