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-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>
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-To: rth@cygnus.com
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-
-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.
projects / binutils-gdb.git / commitdiff