* sched-int.h (ds_to_dk, dk_to_ds): Declare functions.
(struct _dep): New type.
(dep_t): New typedef.
(DEP_PRO, DEP_CON, DEP_KIND): New access macros.
(DEP_STATUS): New access macro. The macro with the same name was
renamed to DEP_LINK_STATUS.
(dep_init): Declare function
(struct _dep_link): New type.
(dep_link_t): New typedef.
(DEP_LINK_NODE, DEP_LINK_NEXT, DEP_LINK_PREV_NEXTP): New access macros.
(DEP_LINK_DEP, DEP_LINK_PRO, DEP_LINK_CON, DEP_LINK_KIND): New macros.
(DEP_LINK_STATUS): New macro.
(debug_dep_links): New debug function.
(struct _deps_list): New type.
(deps_list_t): New typedef.
(DEPS_LIST_FIRST): New access macro.
(FOR_EACH_DEP_LINK): New cycle macro.
(create_deps_list, free_deps_list, delete_deps_list): Declare
functions.
(deps_list_empty_p, debug_deps_list, add_back_dep_to_deps_list): Ditto.
(find_link_by_pro_in_deps_list, find_link_by_con_in_deps_list): Ditto.
(copy_deps_list_change_con): Ditto.
(move_dep_link): Declare function.
(struct _dep_node): New type.
(dep_node_t): New typedef.
(DEP_NODE_BACK, DEP_NODE_DEP, DEP_NODE_FORW): New access macros.
(struct haifa_insn_data.back_deps): New field to hold backward
dependencies of the insn.
(struct haifa_insn_data.depend): Rename to forw_deps. Change its type
to deps_list_t.
(struct haifa_insn_data.resolved_deps): Rename to resolved_back_deps.
Change its type to deps_list_t.
(INSN_BACK_DEPS): New access macro to use instead of LOG_LINKS.
(INSN_DEPEND): Rename to INSN_FORW_DEPS.
(RESOLVED_DEPS): Rename to INSN_RESOLVED_BACK_DEPS.
(INSN_COST): Move to haifa-sched.c. Use insn_cost () instead.
(DEP_STATUS): Rename to DEP_LINK_STATUS. Fix typo in the comment.
(add_forw_dep, delete_back_forw_dep, insn_cost): Update declaration and
all callers.
(dep_cost): Declare.
* sched-deps.c (CHECK): New macro to (en/dis)able sanity checks.
(ds_to_dk, dk_to_ds): New functions.
(init_dep_1): New static function.
(init_dep): New function.
(copy_dep): New static function.
(dep_link_consistent_p, attach_dep_link, add_to_deps_list): New static
functions.
(detach_dep_link): New static function.
(move_dep_link): New function.
(dep_links_consistent_p, dump_dep_links): New static functions.
(debug_dep_links): New debugging function.
(deps_obstack, dl_obstack, dn_obstack): New static variables.
(alloc_deps_list, init_deps_list): New static functions.
(create_deps_list): New function.
(clear_deps_list): New static function.
(free_deps_list, delete_deps_list, deps_list_empty_p): New functions.
(deps_list_consistent_p, dump_deps_list): New static functions.
(debug_deps_list): New function.
(add_back_dep_to_deps_list, find_link_by_pro_in_deps_list): New
functions.
(find_link_by_con_in_deps_list, copy_deps_list_change_con): Ditto.
(maybe_add_or_update_back_dep_1, add_or_update_back_dep_1): Update to
use new scheduler dependencies lists.
(add_back_dep, delete_all_dependences, fixup_sched_groups): Ditto.
(sched_analyze): Ditto. Initialize dependencies lists.
(add_forw_dep, compute_forward_dependences): Update to use new
scheduler dependencies lists.
(init_dependency_caches): Init deps_obstack.
(free_dependency_caches): Free deps_obstack.
(adjust_add_sorted_back_dep, adjust_back_add_forw_dep): Update to use
new scheduler dependencies lists.
(delete_forw_dep, add_or_update_back_forw_dep): Ditto.
(add_back_forw_dep, delete_back_forw_dep): Ditto.
* sched-rgn.c (set_spec_fed, find_conditional_protection, is_pfree):
Update to use new scheduler dependencies lists.
(is_conditionally_protected, is_prisky, add_branch_dependences): Ditto.
(debug_dependencies): Ditto.
(schedule_region): Update comments.
* sched-ebb.c (earliest_block_with_similiar_load): Update to use new
scheduler dependencies lists.
(schedule_ebb): Update comments.
* rtl.def (DEPS_LIST): Remove.
* lists.c (unused_deps_list): Remove.
(free_list): Update assertions.
(alloc_DEPS_LIST, free_DEPS_LIST_list, free_DEPS_LIST_node): Remove.
(remove_free_DEPS_LIST_elem, copy_DEPS_LIST_list): Ditto.
* rtl.h (free_DEPS_LIST_list, alloc_DEPS_LIST): Remove declarations.
(remove_free_DEPS_LIST_elem, copy_DEPS_LIST_list): Ditto.
* haifa-sched.c (comments): Update.
(insn_cost1): Remove. Inline the code into insn_cost ().
(insn_cost): Update to use new scheduler dependencies lists. Move
processing of the dependency cost to dep_cost ().
(dep_cost): New function. Use it instead of insn_cost () when
evaluating cost of the dependency. Use compatible interface to
interact with the target.
(priority): Update to use new scheduler dependencies lists.
(rank_for_schedule): Ditto. Optimize heuristic that prefers the insn
with greater number of insns that depend on the insn.
(schedule_insn): Update to use new scheduler dependencies lists. Add
code to free backward dependencies lists. Inline and optimize code
from resolve_dep () - see PR28071.
(ok_for_early_queue_removal): Update to use new scheduler dependencies
lists. Update call to targetm.sched.is_costly_dependence hook.
(fix_inter_tick, try_ready, fix_tick_ready): Update to use new
scheduler dependencies lists.
(resolve_dep): Remove. Move the logic to schedule_insn ().
(init_h_i_d): Initialize dependencies lists.
(process_insn_depend_be_in_spec): Rename to
process_insn_forw_deps_be_in_spec. Update to use new scheduler
dependencies lists.
(add_to_speculative_block, create_check_block_twin, fix_recovery_deps):
Update to use new scheduler dependencies lists.
(clear_priorities, calc_priorities, add_jump_dependencies): Ditto.
* ddg.c (create_ddg_dependence, create_ddg_dep_no_link): Update to use
new scheduler dependencies lists.
(build_intra_loop_deps): Ditto.
* target.h (struct _dep): Declare to use in
gcc_target.sched.is_costly_dependence.
(struct gcc_target.sched.adjust_cost): Fix typo.
(struct gcc_target.sched.is_costly_dependence): Change signature to use
single dep_t parameter instead of an equivalent triad.
(struct gcc_target.sched.adjust_cost_2): Remove.
* target-def.h (TARGET_SCHED_ADJUST_COST_2): Remove.
* reg-notes.def (DEP_TRUE, DEP_OUTPUT, DEP_ANTI): Update comments.
* doc/tm.texi (TARGET_SCHED_IS_COSTLY_DEPENDENCE): Update
documentation.
(TARGET_SCHED_ADJUST_COST_2): Remove documentation.
* doc/rtl.texi (LOG_LINKS): Remove part about instruction scheduler.
(REG_DEP_TRUE): Document.
* config/ia64/ia64.c (ia64_adjust_cost_2): Rename to ia64_adjust_cost.
Change signature to correspond to the targetm.sched.adjust_cost hook.
Update use in TARGET_SCHED_ADJUST_COST_2.
(TARGET_SCHED_ADJUST_COST_2): Rename to TARGET_SCHED_ADJUST_COST.
(ia64_dependencies_evaluation_hook, ia64_dfa_new_cycle): Update to use
new scheduler dependencies lists.
(ia64_gen_check): Ditto.
* config/mips/mips.c (vr4130_swap_insns_p): Update to use new scheduler
dependencies lists.
* config/rs6000/rs6000.c (rs6000_is_costly_dependence): Change
signature to correspond to the targetm.sched.is_costly_dependence hook.
(is_costly_group): Update to use new scheduler dependencies lists.
* config/spu/spu.c (spu_sched_adjust_cost): Use insn_cost () function
instead of INSN_COST () macro.
From-SVN: r121494
Copyright (C) 2000, 2003 Free Software Foundation, Inc.
This file is intended to contain a few notes about writing C code
within GCC so that it compiles without error on the full range of
compilers GCC needs to be able to compile on.
The problem is that many ISO-standard constructs are not accepted by
either old or buggy compilers, and we keep getting bitten by them.
This knowledge until know has been sparsely spread around, so I
thought I'd collect it in one useful place. Please add and correct
any problems as you come across them.
I'm going to start from a base of the ISO C90 standard, since that is
probably what most people code to naturally. Obviously using
constructs introduced after that is not a good idea.
For the complete coding style conventions used in GCC, please read
http://gcc.gnu.org/codingconventions.html
String literals
---------------
Irix6 "cc -n32" and OSF4 "cc" have problems with constant string
initializers with parens around it, e.g.
const char string[] = ("A string");
This is unfortunate since this is what the GNU gettext macro N_
produces. You need to find a different way to code it.
Some compilers like MSVC++ have fairly low limits on the maximum
length of a string literal; 509 is the lowest we've come across. You
may need to break up a long printf statement into many smaller ones.
Empty macro arguments
---------------------
ISO C (6.8.3 in the 1990 standard) specifies the following:
If (before argument substitution) any argument consists of no
preprocessing tokens, the behavior is undefined.
This was relaxed by ISO C99, but some older compilers emit an error,
so code like
#define foo(x, y) x y
foo (bar, )
needs to be coded in some other way.
free and realloc
----------------
Some implementations crash upon attempts to free or realloc the null
pointer. Thus if mem might be null, you need to write
if (mem)
free (mem);
Trigraphs
---------
You weren't going to use them anyway, but some otherwise ISO C
compliant compilers do not accept trigraphs.
Suffixes on Integer Constants
-----------------------------
You should never use a 'l' suffix on integer constants ('L' is fine),
since it can easily be confused with the number '1'.
Common Coding Pitfalls
======================
errno
-----
errno might be declared as a macro.
Implicit int
------------
In C, the 'int' keyword can often be omitted from type declarations.
For instance, you can write
unsigned variable;
as shorthand for
unsigned int variable;
There are several places where this can cause trouble. First, suppose
'variable' is a long; then you might think
(unsigned) variable
would convert it to unsigned long. It does not. It converts to
unsigned int. This mostly causes problems on 64-bit platforms, where
long and int are not the same size.
Second, if you write a function definition with no return type at
all:
operate (int a, int b)
{
...
}
that function is expected to return int, *not* void. GCC will warn
about this.
Implicit function declarations always have return type int. So if you
correct the above definition to
void
operate (int a, int b)
...
but operate() is called above its definition, you will get an error
about a "type mismatch with previous implicit declaration". The cure
is to prototype all functions at the top of the file, or in an
appropriate header.
Char vs unsigned char vs int
----------------------------
In C, unqualified 'char' may be either signed or unsigned; it is the
implementation's choice. When you are processing 7-bit ASCII, it does
not matter. But when your program must handle arbitrary binary data,
or fully 8-bit character sets, you have a problem. The most obvious
issue is if you have a look-up table indexed by characters.
For instance, the character '\341' in ISO Latin 1 is SMALL LETTER A
WITH ACUTE ACCENT. In the proper locale, isalpha('\341') will be
true. But if you read '\341' from a file and store it in a plain
char, isalpha(c) may look up character 225, or it may look up
character -31. And the ctype table has no entry at offset -31, so
your program will crash. (If you're lucky.)
It is wise to use unsigned char everywhere you possibly can. This
avoids all these problems. Unfortunately, the routines in <string.h>
take plain char arguments, so you have to remember to cast them back
and forth - or avoid the use of strxxx() functions, which is probably
a good idea anyway.
Another common mistake is to use either char or unsigned char to
receive the result of getc() or related stdio functions. They may
return EOF, which is outside the range of values representable by
char. If you use char, some legal character value may be confused
with EOF, such as '\377' (SMALL LETTER Y WITH UMLAUT, in Latin-1).
The correct choice is int.
A more subtle version of the same mistake might look like this:
unsigned char pushback[NPUSHBACK];
int pbidx;
#define unget(c) (assert(pbidx < NPUSHBACK), pushback[pbidx++] = (c))
#define get(c) (pbidx ? pushback[--pbidx] : getchar())
...
unget(EOF);
which will mysteriously turn a pushed-back EOF into a SMALL LETTER Y
WITH UMLAUT.
Other common pitfalls
---------------------
o Expecting 'plain' char to be either sign or unsigned extending.
o Shifting an item by a negative amount or by greater than or equal to
the number of bits in a type (expecting shifts by 32 to be sensible
has caused quite a number of bugs at least in the early days).
o Expecting ints shifted right to be sign extended.
o Modifying the same value twice within one sequence point.
o Host vs. target floating point representation, including emitting NaNs
and Infinities in a form that the assembler handles.
o qsort being an unstable sort function (unstable in the sense that
multiple items that sort the same may be sorted in different orders
by different qsort functions).
o Passing incorrect types to fprintf and friends.
o Adding a function declaration for a module declared in another file to
a .c file instead of to a .h file.