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| -rw-r--r-- | gdb/doc/LRS | 722 |
1 files changed, 193 insertions, 529 deletions
diff --git a/gdb/doc/LRS b/gdb/doc/LRS index 5cd719e..eb0d711 100644 --- a/gdb/doc/LRS +++ b/gdb/doc/LRS @@ -1,531 +1,195 @@ -Return-Path: owner-egcs@cygnus.com Sun -Received: from cygnus.com (runyon.cygnus.com [205.180.230.5]) by hurl.cygnus.com with ESMTP (8.7.1/8.7.1) id RAA11988 for <law@hurl.cygnus.com>; Sun, 5 Oct 1997 17:27:27 -0600 (MDT) -Received: (from majordom@localhost) - by runyon.cygnus.com (8.8.7-cygnus/8.8.7) id QAA27817; - Sun, 5 Oct 1997 16:16:45 -0700 (PDT) -Received: from YALPH1.physics.yale.edu (hepvms1.physics.yale.edu [198.125.138.1]) - by runyon.cygnus.com (8.8.7-cygnus/8.8.7) with ESMTP id QAA27802; - Sun, 5 Oct 1997 16:16:38 -0700 (PDT) -Received: from hepunix2.physics.yale.edu by hepmail.physics.yale.edu - (PMDF V5.1-8 #17719) - with ESMTP id <01IOGJ0WO510CFQE02@hepmail.physics.yale.edu>; Sun, - 5 Oct 1997 19:20:08 EDT -Received: from hepunix1.physics.yale.edu by hepunix.physics.yale.edu - (PMDF V5.1-5 #17721) with SMTP id <0EHLPVM0N00788@hepunix.physics.yale.edu>; - Sun, 05 Oct 1997 19:14:13 -0400 (EDT) -Date: Sun, 05 Oct 1997 19:14:09 -0400 (EDT) -From: Weiwen Liu <liu@hepvms.physics.yale.edu> -Subject: Re: complex support on alpha -In-reply-to: <199710020532.WAA16123@dot.cygnus.com> -X-Sender: liu@hepunix1.physics.yale.edu -To: rth@cygnus.com -Cc: egcs@cygnus.com -Message-id: <Pine.OSF.3.96.971005190110.31383A-100000@hepunix1.physics.yale.edu> -MIME-version: 1.0 -Content-type: TEXT/PLAIN; charset=US-ASCII -Sender: owner-egcs@cygnus.com -Precedence: bulk - -On Wed, 1 Oct 1997, Richard Henderson wrote: - -> Well, it is enough to compile those examples properly, but it is -> not completely correct. The problem is that complex numbers should -> be treated as two distinct arguments on Alpha, which affects padding -> of the arguments passed on the stack. -> - -Here is a patch for it. It should be applied against egcs-970929. -Beside fixing complex-5.c in the testsuite, egcs with this patch generates -the same result from 'make check-gcc' as without it. - -On an alpha-dec-osf4.0, this patch correctly compiles the following test -program with F=char, short, int, long, float, double: -#ifndef F -#define F float -#endif - -typedef __complex__ F FC; - -FC f1(int odd, FC a, FC b, FC c) -{ - return a + b + c; -} - -FC f2a(F a, F b, F c, F d, F e, F f, F g, F h) -{ - return (a + c + e + g) + 1i * (b + d + f + h); -} - -FC f2b(FC a, FC b, FC c, FC d) -{ - return a + b + c + d; -} - -int main() -{ - FC a, b, c, d, e; - a = 1 + 2i; - b = 3+4i; - c = 5+6i; - d = 7+8i; - - e = f1(1,a,b,c); - if (e != 9+12i) - abort (); - e=f2b(a,b,c,d); - if (e != 16+20i) - abort (); - e=f2a(1,2,3,4,5,6,7,8); - if (e != 16+20i) - abort (); - return 0; -} - -This patch has only been tested on alpha-dec-osf4.0, because I have no -access to other machines. To support compless on other machines, the -machine-dependent tm.h has to be modified similarly to what is done for -alpha.h here. - -Weiwen - -Sun Oct 5 19:00:00 Weiwen Liu <liu@hepunix.phycis.yale.edu> - - * c-tree.h: Define complex_long_integer_type_node - to support __complex__ long. - * c-decl.c (init_decl_processing): Initialize - complex_long_integer_type_node. - * c-lex.c (yylex): Enable __complex__ long. - - * expr.h: Define COMPLEX_WORD_MODE and GET_COMPLEX_MODE_SIZE. - * emit-rtl.c (gen_lowpart_common, gen_highpart, - operand_subword): Use them. - * expr.c (move_block_to_reg, emit_push_insn): Use them. - - * emit-rtl.c (operand_subword): Deal with a complex mode. - - * regs.h: Correctly calculate REG_SIZE for a complex mode. - - * config/alpha/alpha.h: Correctly deal with a complex mode in - HARD_REGNO_NREGS, FUNCTION_VALUE, ALPHA_ARG_SIZE. - -*** gcc/c-decl.c.orig Sat Sep 27 14:16:06 1997 ---- gcc/c-decl.c Wed Oct 1 16:19:39 1997 -*************** tree double_type_node; -*** 135,140 **** ---- 135,141 ---- - tree long_double_type_node; - - tree complex_integer_type_node; -+ tree complex_long_integer_type_node; - tree complex_float_type_node; - tree complex_double_type_node; - tree complex_long_double_type_node; -*************** init_decl_processing () -*** 2989,2994 **** ---- 2990,3001 ---- - complex_integer_type_node)); - TREE_TYPE (complex_integer_type_node) = integer_type_node; - layout_type (complex_integer_type_node); -+ -+ complex_long_integer_type_node = make_node (COMPLEX_TYPE); -+ pushdecl (build_decl (TYPE_DECL, get_identifier ("complex long int"), -+ complex_long_integer_type_node)); -+ TREE_TYPE (complex_long_integer_type_node) = long_integer_type_node; -+ layout_type (complex_long_integer_type_node); - - complex_float_type_node = make_node (COMPLEX_TYPE); - pushdecl (build_decl (TYPE_DECL, get_identifier ("complex float"), -*** gcc/c-lex.c.orig Fri Aug 15 01:32:53 1997 ---- gcc/c-lex.c Wed Oct 1 16:19:39 1997 -*************** yylex () -*** 1769,1774 **** ---- 1769,1780 ---- - = build_complex (NULL_TREE, integer_zero_node, - convert (integer_type_node, - yylval.ttype)); -+ else if (TYPE_PRECISION (type) -+ <= TYPE_PRECISION (long_integer_type_node)) -+ yylval.ttype -+ = build_complex (NULL_TREE, integer_zero_node, -+ convert (long_integer_type_node, -+ yylval.ttype)); - else - error ("complex integer constant is too wide for `complex int'"); - } -*** gcc/c-tree.h.orig Mon Aug 11 11:57:03 1997 ---- gcc/c-tree.h Wed Oct 1 16:19:40 1997 -*************** extern tree long_long_integer_type_node; -*** 219,224 **** ---- 219,225 ---- - extern tree long_long_unsigned_type_node; - extern tree long_unsigned_type_node; - extern tree complex_integer_type_node; -+ extern tree complex_long_integer_type_node; - extern tree complex_float_type_node; - extern tree complex_double_type_node; - extern tree complex_long_double_type_node; -*** gcc/emit-rtl.c.orig Mon Sep 22 13:41:24 1997 ---- gcc/emit-rtl.c Sun Oct 5 17:48:05 1997 -*************** gen_lowpart_common (mode, x) -*** 635,644 **** - / UNITS_PER_WORD))) - return 0; - -! if (WORDS_BIG_ENDIAN && GET_MODE_SIZE (GET_MODE (x)) > UNITS_PER_WORD) -! word = ((GET_MODE_SIZE (GET_MODE (x)) -! - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD)) -! / UNITS_PER_WORD); - - if ((GET_CODE (x) == ZERO_EXTEND || GET_CODE (x) == SIGN_EXTEND) - && (GET_MODE_CLASS (mode) == MODE_INT ---- 635,644 ---- - / UNITS_PER_WORD))) - return 0; - -! if (WORDS_BIG_ENDIAN && GET_MODE_SIZE (GET_MODE (x)) >0) -! word = GET_COMPLEX_MODE_SIZE (GET_MODE (x)) -! - ((GET_MODE_SIZE (mode) + (UNITS_PER_WORD - 1)) -! / UNITS_PER_WORD); - - if ((GET_CODE (x) == ZERO_EXTEND || GET_CODE (x) == SIGN_EXTEND) - && (GET_MODE_CLASS (mode) == MODE_INT -*************** gen_highpart (mode, x) -*** 1013,1022 **** - int word = 0; - - if (! WORDS_BIG_ENDIAN -! && GET_MODE_SIZE (GET_MODE (x)) > UNITS_PER_WORD) -! word = ((GET_MODE_SIZE (GET_MODE (x)) -! - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD)) -! / UNITS_PER_WORD); - - /* - * ??? This fails miserably for complex values being passed in registers ---- 1013,1022 ---- - int word = 0; - - if (! WORDS_BIG_ENDIAN -! && GET_MODE_SIZE (GET_MODE (x)) > 0) -! word = GET_COMPLEX_MODE_SIZE (GET_MODE (x)) -! - ((GET_MODE_SIZE (mode) + (UNITS_PER_WORD - 1)) -! / UNITS_PER_WORD); - - /* - * ??? This fails miserably for complex values being passed in registers -*************** operand_subword (op, i, validate_address -*** 1100,1105 **** ---- 1100,1107 ---- - - /* If OP is narrower than a word or if we want a word outside OP, fail. */ - if (mode != BLKmode -+ && (GET_MODE_CLASS (mode) != MODE_COMPLEX_INT -+ && GET_MODE_CLASS (mode) != MODE_COMPLEX_FLOAT) - && (GET_MODE_SIZE (mode) < UNITS_PER_WORD - || (i + 1) * UNITS_PER_WORD > GET_MODE_SIZE (mode))) - return 0; -*************** operand_subword (op, i, validate_address -*** 1127,1133 **** - || op == arg_pointer_rtx - #endif - || op == stack_pointer_rtx) -! return gen_rtx (SUBREG, word_mode, op, i); - else - return gen_rtx (REG, word_mode, REGNO (op) + i); - } ---- 1129,1135 ---- - || op == arg_pointer_rtx - #endif - || op == stack_pointer_rtx) -! return gen_rtx (SUBREG, COMPLEX_WORD_MODE (mode), op, i); - else - return gen_rtx (REG, word_mode, REGNO (op) + i); - } -*************** operand_subword (op, i, validate_address -*** 1135,1141 **** - return gen_rtx (SUBREG, word_mode, SUBREG_REG (op), i + SUBREG_WORD (op)); - else if (GET_CODE (op) == CONCAT) - { -! int partwords = GET_MODE_UNIT_SIZE (GET_MODE (op)) / UNITS_PER_WORD; - if (i < partwords) - return operand_subword (XEXP (op, 0), i, validate_address, mode); - return operand_subword (XEXP (op, 1), i - partwords, ---- 1137,1144 ---- - return gen_rtx (SUBREG, word_mode, SUBREG_REG (op), i + SUBREG_WORD (op)); - else if (GET_CODE (op) == CONCAT) - { -! int partwords = (GET_MODE_UNIT_SIZE (GET_MODE (op)) -! + (UNITS_PER_WORD - 1))/ UNITS_PER_WORD; - if (i < partwords) - return operand_subword (XEXP (op, 0), i, validate_address, mode); - return operand_subword (XEXP (op, 1), i - partwords, -*************** operand_subword (op, i, validate_address -*** 1145,1151 **** - /* Form a new MEM at the requested address. */ - if (GET_CODE (op) == MEM) - { -! rtx addr = plus_constant (XEXP (op, 0), i * UNITS_PER_WORD); - rtx new; - - if (validate_address) ---- 1148,1158 ---- - /* Form a new MEM at the requested address. */ - if (GET_CODE (op) == MEM) - { -! rtx addr = plus_constant ( -! XEXP (op, 0), -! (GET_MODE_CLASS (mode) == MODE_COMPLEX_INT -! || GET_MODE_CLASS (mode) == MODE_COMPLEX_FLOAT)? -! i*GET_MODE_UNIT_SIZE (mode): i * UNITS_PER_WORD); - rtx new; - - if (validate_address) -*************** operand_subword (op, i, validate_address -*** 1159,1165 **** - addr = memory_address (word_mode, addr); - } - -! new = gen_rtx (MEM, word_mode, addr); - - MEM_VOLATILE_P (new) = MEM_VOLATILE_P (op); - MEM_IN_STRUCT_P (new) = MEM_IN_STRUCT_P (op); ---- 1166,1172 ---- - addr = memory_address (word_mode, addr); - } - -! new = gen_rtx (MEM, COMPLEX_WORD_MODE (mode), addr); - - MEM_VOLATILE_P (new) = MEM_VOLATILE_P (op); - MEM_IN_STRUCT_P (new) = MEM_IN_STRUCT_P (op); -*** gcc/expr.c.orig Sat Oct 4 03:12:35 1997 ---- gcc/expr.c Sun Oct 5 18:21:18 1997 -*************** move_block_to_reg (regno, x, nregs, mode -*** 1701,1707 **** - #endif - - for (i = 0; i < nregs; i++) -! emit_move_insn (gen_rtx (REG, word_mode, regno + i), - operand_subword_force (x, i, mode)); - } - ---- 1701,1707 ---- - #endif - - for (i = 0; i < nregs; i++) -! emit_move_insn (gen_rtx (REG, COMPLEX_WORD_MODE (mode), regno + i), - operand_subword_force (x, i, mode)); - } - -*************** move_block_from_reg (regno, x, nregs, si -*** 1724,1729 **** ---- 1724,1731 ---- - /* If SIZE is that of a mode no bigger than a word, just use that - mode's store operation. */ - if (size <= UNITS_PER_WORD -+ && GET_MODE_CLASS (GET_MODE (x)) != MODE_COMPLEX_INT -+ && GET_MODE_CLASS (GET_MODE (x)) != MODE_COMPLEX_FLOAT - && (mode = mode_for_size (size * BITS_PER_UNIT, MODE_INT, 0)) != BLKmode) - { - emit_move_insn (change_address (x, mode, NULL), -*************** move_block_from_reg (regno, x, nregs, si -*** 1769,1780 **** - - for (i = 0; i < nregs; i++) - { -! rtx tem = operand_subword (x, i, 1, BLKmode); - - if (tem == 0) - abort (); - -! emit_move_insn (tem, gen_rtx (REG, word_mode, regno + i)); - } - } - ---- 1771,1786 ---- - - for (i = 0; i < nregs; i++) - { -! rtx tem = operand_subword -! (x, i, 1, (GET_MODE_CLASS(GET_MODE (x)) == MODE_COMPLEX_INT -! || GET_MODE_CLASS(GET_MODE (x)) == MODE_COMPLEX_FLOAT)? -! GET_MODE(x):BLKmode); - - if (tem == 0) - abort (); - -! emit_move_insn (tem, gen_rtx (REG, COMPLEX_WORD_MODE (GET_MODE (x)), -! regno + i)); - } - } - -*************** emit_push_insn (x, mode, type, size, ali -*** 2687,2693 **** - { - /* Scalar partly in registers. */ - -! int size = GET_MODE_SIZE (mode) / UNITS_PER_WORD; - int i; - int not_stack; - /* # words of start of argument ---- 2693,2699 ---- - { - /* Scalar partly in registers. */ - -! int size = GET_COMPLEX_MODE_SIZE (mode); - int i; - int not_stack; - /* # words of start of argument -*************** emit_push_insn (x, mode, type, size, ali -*** 2696,2701 **** ---- 2702,2716 ---- - int args_offset = INTVAL (args_so_far); - int skip; - -+ /* For a complex argument passing partially in a register, -+ save the image part in stack immedially following the space -+ used for save the part passig in register (see function -+ assign_parms in function.c). */ -+ if (GET_MODE_CLASS (mode) == MODE_COMPLEX_INT -+ || GET_MODE_CLASS (mode) == MODE_COMPLEX_FLOAT) -+ if (GET_MODE_UNIT_SIZE (mode) < UNITS_PER_WORD) -+ args_offset += GET_MODE_UNIT_SIZE (mode) - UNITS_PER_WORD; -+ - /* Push padding now if padding above and stack grows down, - or if padding below and stack grows up. - But if space already allocated, this has already been done. */ -*************** emit_push_insn (x, mode, type, size, ali -*** 2742,2748 **** - #endif - if (i >= not_stack + offset) - emit_push_insn (operand_subword_force (x, i, mode), -! word_mode, NULL_TREE, NULL_RTX, align, 0, NULL_RTX, - 0, args_addr, - GEN_INT (args_offset + ((i - not_stack + skip) - * UNITS_PER_WORD))); ---- 2757,2764 ---- - #endif - if (i >= not_stack + offset) - emit_push_insn (operand_subword_force (x, i, mode), -! COMPLEX_WORD_MODE (mode), -! NULL_TREE, NULL_RTX, align, 0, NULL_RTX, - 0, args_addr, - GEN_INT (args_offset + ((i - not_stack + skip) - * UNITS_PER_WORD))); -*** gcc/expr.h.orig Sat Oct 4 23:46:34 1997 ---- gcc/expr.h Sun Oct 5 18:21:14 1997 -*************** extern void bc_adjust_stack PROTO ((in -*** 952,954 **** ---- 952,970 ---- - extern void bc_load_localaddr PROTO ((rtx)); - extern void do_jump_by_parts_greater_rtx PROTO ((enum machine_mode, int, - rtx, rtx, rtx, rtx)); -+ -+ /* Determine the mode for the imagine and real part of a complex MODE. -+ For a non-complex MODE, use WORD_MODE.*/ -+ #define COMPLEX_WORD_MODE(MODE) \ -+ (((GET_MODE_CLASS (MODE) == MODE_COMPLEX_INT \ -+ || GET_MODE_CLASS (MODE) == MODE_COMPLEX_FLOAT) \ -+ && GET_MODE_UNIT_SIZE (MODE) < UNITS_PER_WORD)? \ -+ mode_for_size (GET_MODE_UNIT_SIZE(MODE)*BITS_PER_UNIT, \ -+ (GET_MODE_CLASS (MODE) == MODE_COMPLEX_INT)? \ -+ MODE_INT:MODE_FLOAT, \ -+ 0):word_mode) -+ -+ /* Calculate number of bytes needed for a complex MODE */ -+ #define GET_COMPLEX_MODE_SIZE(MODE) \ -+ (((GET_MODE_UNIT_SIZE (MODE) + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD) \ -+ * (GET_MODE_SIZE (MODE)) / GET_MODE_UNIT_SIZE (MODE)) -*** gcc/regs.h.orig Mon Aug 11 11:57:12 1997 ---- gcc/regs.h Wed Oct 1 16:19:31 1997 -*************** Boston, MA 02111-1307, USA. */ -*** 27,33 **** - valid way to get this value. You cannot get it from the regno. */ - - #define REG_SIZE(R) \ -! ((mode_size[(int) GET_MODE (R)] + UNITS_PER_WORD - 1) / UNITS_PER_WORD) - - /* Maximum register number used in this function, plus one. */ - ---- 27,36 ---- - valid way to get this value. You cannot get it from the regno. */ - - #define REG_SIZE(R) \ -! (GET_MODE_SIZE (GET_MODE (R)) == 0? \ -! 0:(((GET_MODE_UNIT_SIZE (GET_MODE (R)) + (UNITS_PER_WORD - 1)) \ -! / UNITS_PER_WORD) * (GET_MODE_SIZE (GET_MODE (R)) \ -! / GET_MODE_UNIT_SIZE (GET_MODE (R))))) - - /* Maximum register number used in this function, plus one. */ - -*** gcc/config/alpha/alpha.h.orig Wed Oct 1 16:16:31 1997 ---- gcc/config/alpha/alpha.h Fri Oct 3 11:41:58 1997 -*************** extern void override_options (); -*** 515,521 **** - but can be less for certain modes in special long registers. */ - - #define HARD_REGNO_NREGS(REGNO, MODE) \ -! ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) / UNITS_PER_WORD) - - /* Value is 1 if hard register REGNO can hold a value of machine-mode MODE. - On Alpha, the integer registers can hold any mode. The floating-point ---- 515,524 ---- - but can be less for certain modes in special long registers. */ - - #define HARD_REGNO_NREGS(REGNO, MODE) \ -! (GET_MODE_SIZE (MODE) == 0? \ -! 0:(((GET_MODE_UNIT_SIZE (MODE) + (UNITS_PER_WORD - 1)) \ -! / UNITS_PER_WORD) * (GET_MODE_SIZE (MODE) \ -! / GET_MODE_UNIT_SIZE (MODE)))) - - /* Value is 1 if hard register REGNO can hold a value of machine-mode MODE. - On Alpha, the integer registers can hold any mode. The floating-point -*************** enum reg_class { NO_REGS, GENERAL_REGS, -*** 891,901 **** - #define FUNCTION_VALUE(VALTYPE, FUNC) \ - gen_rtx (REG, \ - (INTEGRAL_MODE_P (TYPE_MODE (VALTYPE)) \ - && TYPE_PRECISION (VALTYPE) < BITS_PER_WORD) \ - ? word_mode : TYPE_MODE (VALTYPE), \ - ((TARGET_FPREGS \ - && (TREE_CODE (VALTYPE) == REAL_TYPE \ -! || TREE_CODE (VALTYPE) == COMPLEX_TYPE)) \ - ? 32 : 0)) - - /* Define how to find the value returned by a library function ---- 894,908 ---- - #define FUNCTION_VALUE(VALTYPE, FUNC) \ - gen_rtx (REG, \ - (INTEGRAL_MODE_P (TYPE_MODE (VALTYPE)) \ -+ && (GET_MODE_CLASS(TYPE_MODE (VALTYPE)) \ -+ != MODE_COMPLEX_INT) \ - && TYPE_PRECISION (VALTYPE) < BITS_PER_WORD) \ - ? word_mode : TYPE_MODE (VALTYPE), \ - ((TARGET_FPREGS \ - && (TREE_CODE (VALTYPE) == REAL_TYPE \ -! || TREE_CODE (VALTYPE) == COMPLEX_TYPE) \ -! && (GET_MODE_CLASS(TYPE_MODE (VALTYPE)) \ -! != MODE_COMPLEX_INT)) \ - ? 32 : 0)) - - /* Define how to find the value returned by a library function -*************** enum reg_class { NO_REGS, GENERAL_REGS, -*** 953,959 **** - - #define ALPHA_ARG_SIZE(MODE, TYPE, NAMED) \ - ((MODE) != BLKmode \ -! ? (GET_MODE_SIZE (MODE) + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD \ - : (int_size_in_bytes (TYPE) + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD) - - /* Update the data in CUM to advance over an argument ---- 960,969 ---- - - #define ALPHA_ARG_SIZE(MODE, TYPE, NAMED) \ - ((MODE) != BLKmode \ -! ? (GET_MODE_SIZE (MODE) > 0? \ -! (GET_MODE_UNIT_SIZE (MODE) + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD \ -! * GET_MODE_SIZE (MODE) / GET_MODE_UNIT_SIZE (MODE) \ -! : 0) \ - : (int_size_in_bytes (TYPE) + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD) - - /* Update the data in CUM to advance over an argument +What's LRS? +=========== + +LRS, or Live Range Splitting is an optimization technique which allows a user +variable to reside in different locations during different parts of a function. + +For example, a variable might reside in the stack for part of a function and +in a register during a loop and in a different register during another loop. + +Clearly, if a variable may reside in different locations, then the compiler +must describe to the debugger where the variable resides for any given part +of the function. + +This document describes the debug format for encoding these extensions in +stabs. + +Since these extensions are gcc specific, these additional symbols and stabs +can be disabled by the gcc command option -gstabs. + + +GNU extensions for LRS under stabs: +=================================== + + +range symbols: +------------- + + A range symbol will be used to mark the beginning or end of a live range + (the range which describes where a symbol is active, or live). + These symbols will later be referenced in the stabs for debug purposes. + For simplicity, we'll use the terms "range_start" and "range_end" to + identify the range symbols which mark the beginning and end of a live + range respectively. + + Any text symbol which would normally appear in the symbol table (eg. a + function name) can be used as range symbol. If an address is needed to + delimit a live range and does not match any of the values of symbols + which would normally appear in the symbol table, a new symbol will be + added to the table whose value is that address. + + The three new symbol types described below have been added for this + purpose. + + For efficiency, the compiler should use existing symbols as range symbols + whenever possible; this reduces the number of additional symbols which + need to be added to the symbol table. + + +New debug symbol type for defining ranges: +------------------------------------------ + + range_off - contains PC function offset for start/end of a live range. + Its location is relative to the function start and therefore + eliminates the need for additional relocation. + + This symbol has a values in the text section, and does not have a name. + + NOTE: the following may not be needed but are included here just + in case. + range - contains PC value of beginning or end of a live range + (relocs required). + + NOTE: the following will be required if we desire LRS debugging + to work with old style a.out stabs. + range_abs - contains absolute PC value of start/end of a live + range. The range_abs debug symbol is provided for + completeness, in case there is a need to describe addresses + in ROM, etc. + + +Live range: +----------- + + The compiler and debugger view a variable with multiple homes as a primary + symbol and aliases for that symbol. The primary symbol describes the default + home of the variable while aliases describe alternate homes for the variable. + + A live range defines the interval of instructions beginning with + range_start and ending at range_end-1, and is used to specify a range of + instructions where an alias is active or "live". So, the actual end of + the range will be one less than the value of the range_end symbol. + + Ranges do not have to be nested. Eg. Two ranges may intersect while + each range contains subranges which are not in the other range. + + There does not have to be a 1-1 mapping from range_start to + range_end symbols. Eg. Two range_starts can share the same + range_end, while one symbol's range_start can be another symbol's + range_end. + + When a variable's storage class changes (eg. from stack to register, or + from one register to another), a new symbol entry will be added to + the symbol table with stabs describing the new type, and appropriate + live ranges refering to the variable's initial symbol index. + + For variables which are defined in the source but optimized away, a symbol + should be emitted with the live range l(0,0). + + Live ranges for aliases of a particular variable should always be disjoint. + Overlapping ranges for aliases of the same variable will be treated as + an error by the debugger, and the overlapping range will be ignored. + + If no live range information is given, the live range will be assumed to + span the symbol's entire lexical scope. + + +New stabs string identifiers: +----------------------------- + + "id" in "#id" in the following section refers to a numeric value. + + New stab syntax for live range: l(<ref_from>,<ref_to>) + + <ref_from> - "#id" where #id identifies the text symbol (range symbol) to + use as the start of live range (range_start). The value for + the referenced text symbol is the starting address of the + live range. + + <ref_to> - "#id" where #id identifies the text symbol (range symbol) to + use as the end of live range (range_end). The value for + the referenced text symbol is ONE BYTE PAST the ending + address of the live range. + + + New stab syntax for identifying symbols. + + <def> - "#id=" + + Uses: + <def><name>:<typedef1>... + When used in front of a symbol name, "#id=" defines a + unique reference number for this symbol. The reference + number can be used later when defining aliases for this + symbol. + <def> + When used as the entire stab string, "#id=" identifies this + nameless symbol as being the symbol for which "#id" refers to. + + + <ref> - "#id" where "#id" refers to the symbol for which the string + "#id=" identifies. + Uses: + <ref>:<typedef2>;<liverange>;<liverange>... + Defines an alias for the symbol identified by the reference + number ID. + l(<ref1>,<ref2>) + When used within a live range, "#id" refers to the text + symbol identified by "#id=" to use as the range symbol. + + <liverange> - "l(<ref_from>,<ref_to>)" - specifies a live range for a + symbol. Multiple "l" specifiers can be combined to represent + mutiple live ranges, separated by semicolons. + + + + +Example: +======== + +Consider a program of the form: + + void foo(){ + int a = ...; + ... + while (b--) + c += a; + .. + d = a; + .. + } + +Assume that "a" lives in the stack at offset -8, except for inside the loop where +"a" resides in register "r5". + +The way to describe this is to create a stab for the variable "a" which describes +"a" as living in the stack and an alias for the variable "a" which describes it +as living in register "r5" in the loop. + +Let's assume that "#1" and "#2" are symbols which bound the area where "a" lives +in a register. + +The stabs to describe "a" and its alias would look like this: + + .stabs "#3=a:1",128,0,8,-8 + .stabs "#3:r1;l(#1,#2)",64,0,0,5 + + + + +This design implies that the debugger will keep a chain of aliases for any +given variable with aliases and that chain will be searched first to find +out if an alias is active. If no alias is active, then the debugger will +assume that the main variable is active. |