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alias.c (nonlocal_reference_p): Take a care for CALL_INSNS's fusage field. 

* alias.c (nonlocal_reference_p): Take a care for
	CALL_INSNS's fusage field.
	* calls.c (ECF_PURE): New flag.
	(emit_call_1): Handle ECF_PURE calls.
	(initialize_argument_information): Unset ECF_PURE flag too.
	(precompute_arguments): Precompute for ECF_PURE too.
	(expand_call): Handle ECF_PURE calls too.
	(emit_library_call_value_1): Rename no_queue argument to
	fn_type, accept value of 2 as pure function.
	(emit_library_call_value, emit_library_call): Rename no_queue argument
	to fn_type.
	* optabs.c (prepare_cmp_insn): Pass fn_type 2 to memcmp call.

	* tree.h (DECL_IS_PURE): New macro.
	(struct tree_decl): Add pure_flag.
	* c-common.c (enum attrs): Add attribute "pure".
	(init_attributes): Initialize attribute "pure"
	(decl_attributes): Handle attribute "pure".
	* extend.texi (Attribute "pure"): Document.
	* calls.c (expand_call): Add (mem:BLK (scratch)) to "equal from"
	in pure function.
	(flags_from_decl_or_type): Support attribute "pure".

From-SVN: r33138
This commit is contained in:
Jan Hubicka 2000-04-13 13:59:00 +00:00 committed by Jan Hubicka
parent c966901c24
commit 2a8f6b90c1
7 changed files with 143 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
gcc/ChangeLog
View File

@ -1,3 +1,28 @@
Thu Apr 13 15:55:08 MET DST 2000 Jan Hubicka <jh@suse.cz>
* alias.c (nonlocal_reference_p): Take a care for
CALL_INSNS's fusage field.
* calls.c (ECF_PURE): New flag.
(emit_call_1): Handle ECF_PURE calls.
(initialize_argument_information): Unset ECF_PURE flag too.
(precompute_arguments): Precompute for ECF_PURE too.
(expand_call): Handle ECF_PURE calls too.
(emit_library_call_value_1): Rename no_queue argument to
fn_type, accept value of 2 as pure function.
(emit_library_call_value, emit_library_call): Rename no_queue argument
to fn_type.
* optabs.c (prepare_cmp_insn): Pass fn_type 2 to memcmp call.
* tree.h (DECL_IS_PURE): New macro.
(struct tree_decl): Add pure_flag.
* c-common.c (enum attrs): Add attribute "pure".
(init_attributes): Initialize attribute "pure"
(decl_attributes): Handle attribute "pure".
* extend.texi (Attribute "pure"): Document.
* calls.c (expand_call): Add (mem:BLK (scratch)) to "equal from"
in pure function.
(flags_from_decl_or_type): Support attribute "pure".
2000-04-13 Jason Merrill <jason@casey.cygnus.com>
* cpplex.c (_cpp_lex_token): Handle digraphs. Don't null-terminate

13
gcc/alias.c
View File

@ -1424,10 +1424,15 @@ nonlocal_reference_p (x)
if (GET_RTX_CLASS (code) == 'i')
{
/* Constant functions are constant. */
/* Constant functions can be constant if they don't use
scratch memory used to mark function w/o side effects. */
if (code == CALL_INSN && CONST_CALL_P (x))
return 0;
x = PATTERN (x);
{
x = CALL_INSN_FUNCTION_USAGE (x);
if (!x) return 0;
}
else
x = PATTERN (x);
code = GET_CODE (x);
}
@ -1520,7 +1525,7 @@ nonlocal_reference_p (x)
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
if (fmt[i] == 'e')
if (fmt[i] == 'e' && XEXP (x, i))
{
if (nonlocal_reference_p (XEXP (x, i)))
return 1;

13
gcc/c-common.c
View File

@ -145,7 +145,7 @@ enum attrs {A_PACKED, A_NOCOMMON, A_COMMON, A_NORETURN, A_CONST, A_T_UNION,
A_NO_CHECK_MEMORY_USAGE, A_NO_INSTRUMENT_FUNCTION,
A_CONSTRUCTOR, A_DESTRUCTOR, A_MODE, A_SECTION, A_ALIGNED,
A_UNUSED, A_FORMAT, A_FORMAT_ARG, A_WEAK, A_ALIAS, A_MALLOC,
A_NO_LIMIT_STACK};
A_NO_LIMIT_STACK, A_PURE};
enum format_type { printf_format_type, scanf_format_type,
strftime_format_type };
@ -457,6 +457,7 @@ init_attributes ()
add_attribute (A_NO_CHECK_MEMORY_USAGE, "no_check_memory_usage", 0, 0, 1);
add_attribute (A_MALLOC, "malloc", 0, 0, 1);
add_attribute (A_NO_LIMIT_STACK, "no_stack_limit", 0, 0, 1);
add_attribute (A_PURE, "pure", 0, 0, 1);
}
/* Default implementation of valid_lang_attribute, below. By default, there
@ -596,6 +597,7 @@ decl_attributes (node, attributes, prefix_attributes)
case A_MALLOC:
if (TREE_CODE (decl) == FUNCTION_DECL)
DECL_IS_MALLOC (decl) = 1;
/* ??? TODO: Support types. */
else
warning ("`%s' attribute ignored", IDENTIFIER_POINTER (name));
break;
@ -625,6 +627,15 @@ decl_attributes (node, attributes, prefix_attributes)
warning ( "`%s' attribute ignored", IDENTIFIER_POINTER (name));
break;
case A_PURE:
if (TREE_CODE (decl) == FUNCTION_DECL)
DECL_IS_PURE (decl) = 1;
/* ??? TODO: Support types. */
else
warning ("`%s' attribute ignored", IDENTIFIER_POINTER (name));
break;
case A_T_UNION:
if (is_type
&& TREE_CODE (type) == UNION_TYPE

101
gcc/calls.c
View File

@ -168,6 +168,9 @@ static int calls_function_1 PARAMS ((tree, int));
the current one. */
#define ECF_FORK_OR_EXEC 128
#define ECF_SIBCALL 256
/* Nonzero if this is a call to "pure" function (like const function,
but may read memory. */
#define ECF_PURE 512
static void emit_call_1 PARAMS ((rtx, tree, tree, HOST_WIDE_INT,
HOST_WIDE_INT, HOST_WIDE_INT, rtx,
@ -555,6 +558,15 @@ emit_call_1 (funexp, fndecl, funtype, stack_size, rounded_stack_size,
if (! call_insn)
abort ();
/* Mark memory as used for "pure" function call. */
if (ecf_flags & ECF_PURE)
{
call_fusage = gen_rtx_EXPR_LIST (VOIDmode,
gen_rtx_USE (VOIDmode,
gen_rtx_MEM (BLKmode,
gen_rtx_SCRATCH (VOIDmode))), call_fusage);
}
/* Put the register usage information on the CALL. If there is already
some usage information, put ours at the end. */
if (CALL_INSN_FUNCTION_USAGE (call_insn))
@ -571,7 +583,7 @@ emit_call_1 (funexp, fndecl, funtype, stack_size, rounded_stack_size,
CALL_INSN_FUNCTION_USAGE (call_insn) = call_fusage;
/* If this is a const call, then set the insn's unchanging bit. */
if (ecf_flags & ECF_CONST)
if (ecf_flags & (ECF_CONST | ECF_PURE))
CONST_CALL_P (call_insn) = 1;
/* If this call can't throw, attach a REG_EH_REGION reg note to that
@ -610,7 +622,7 @@ emit_call_1 (funexp, fndecl, funtype, stack_size, rounded_stack_size,
if (rounded_stack_size != 0)
{
if (flag_defer_pop && inhibit_defer_pop == 0
&& !(ecf_flags & ECF_CONST))
&& !(ecf_flags & (ECF_CONST | ECF_PURE)))
pending_stack_adjust += rounded_stack_size;
else
adjust_stack (rounded_stack_size_rtx);
@ -759,6 +771,10 @@ flags_from_decl_or_type (exp)
if (DECL_P (exp) && DECL_IS_MALLOC (exp))
flags |= ECF_MALLOC;
/* The function exp may have the `pure' attribute. */
if (DECL_P (exp) && DECL_IS_PURE (exp))
flags |= ECF_PURE;
if (TREE_NOTHROW (exp))
flags |= ECF_NOTHROW;
}
@ -1195,7 +1211,7 @@ initialize_argument_information (num_actuals, args, args_size, n_named_args,
MEM_SET_IN_STRUCT_P (copy, AGGREGATE_TYPE_P (type));
store_expr (args[i].tree_value, copy, 0);
*ecf_flags &= ~ECF_CONST;
*ecf_flags &= ~(ECF_CONST | ECF_PURE);
args[i].tree_value = build1 (ADDR_EXPR,
build_pointer_type (type),
@ -1254,7 +1270,7 @@ initialize_argument_information (num_actuals, args, args_size, n_named_args,
/* If this is an addressable type, we cannot pre-evaluate it. Thus,
we cannot consider this function call constant. */
if (TREE_ADDRESSABLE (type))
*ecf_flags &= ~ECF_CONST;
*ecf_flags &= ~(ECF_CONST | ECF_PURE);
/* Compute the stack-size of this argument. */
if (args[i].reg == 0 || args[i].partial != 0
@ -1435,7 +1451,7 @@ precompute_arguments (flags, must_preallocate, num_actuals, args, args_size)
which have already been stored into the stack. */
for (i = 0; i < num_actuals; i++)
if ((flags & ECF_CONST)
if ((flags & (ECF_CONST | ECF_PURE))
|| ((args_size->var != 0 || args_size->constant != 0)
&& calls_function (args[i].tree_value, 1))
|| (must_preallocate
@ -2038,7 +2054,7 @@ expand_call (exp, target, ignore)
if (aggregate_value_p (exp))
{
/* This call returns a big structure. */
flags &= ~ECF_CONST;
flags &= ~(ECF_CONST | ECF_PURE);
#ifdef PCC_STATIC_STRUCT_RETURN
{
@ -2295,7 +2311,7 @@ expand_call (exp, target, ignore)
/* When calling a const function, we must pop the stack args right away,
so that the pop is deleted or moved with the call. */
if (flags & ECF_CONST)
if (flags & (ECF_CONST | ECF_PURE))
NO_DEFER_POP;
/* Don't let pending stack adjusts add up to too much.
@ -2416,7 +2432,7 @@ expand_call (exp, target, ignore)
Also do not make a sibling call. */
flags &= ~ECF_CONST;
flags &= ~(ECF_CONST | ECF_PURE);
must_preallocate = 1;
sibcall_failure = 1;
}
@ -2470,7 +2486,7 @@ expand_call (exp, target, ignore)
/* Now we are about to start emitting insns that can be deleted
if a libcall is deleted. */
if (flags & (ECF_CONST | ECF_MALLOC))
if (flags & (ECF_CONST | ECF_PURE | ECF_MALLOC))
start_sequence ();
old_stack_allocated = stack_pointer_delta - pending_stack_adjust;
@ -2653,7 +2669,7 @@ expand_call (exp, target, ignore)
{
/* When the stack adjustment is pending, we get better code
by combining the adjustments. */
if (pending_stack_adjust && ! (flags & ECF_CONST)
if (pending_stack_adjust && ! (flags & (ECF_CONST | ECF_PURE))
&& ! inhibit_defer_pop)
{
int adjust;
@ -2821,7 +2837,8 @@ expand_call (exp, target, ignore)
Test valreg so we don't crash; may safely ignore `const'
if return type is void. Disable for PARALLEL return values, because
we have no way to move such values into a pseudo register. */
if ((flags & ECF_CONST) && valreg != 0 && GET_CODE (valreg) != PARALLEL)
if ((flags & (ECF_CONST | ECF_PURE))
&& valreg != 0 && GET_CODE (valreg) != PARALLEL)
{
rtx note = 0;
rtx temp = gen_reg_rtx (GET_MODE (valreg));
@ -2840,11 +2857,17 @@ expand_call (exp, target, ignore)
insns = get_insns ();
end_sequence ();
if (flags & ECF_PURE)
note = gen_rtx_EXPR_LIST (VOIDmode,
gen_rtx_USE (VOIDmode,
gen_rtx_MEM (BLKmode,
gen_rtx_SCRATCH (VOIDmode))), note);
emit_libcall_block (insns, temp, valreg, note);
valreg = temp;
}
else if (flags & ECF_CONST)
else if (flags & (ECF_CONST | ECF_PURE))
{
/* Otherwise, just write out the sequence without a note. */
rtx insns = get_insns ();
@ -3171,11 +3194,11 @@ libfunc_nothrow (fun)
The RETVAL parameter specifies whether return value needs to be saved, other
parameters are documented in the emit_library_call function bellow. */
static rtx
emit_library_call_value_1 (retval, orgfun, value, no_queue, outmode, nargs, p)
emit_library_call_value_1 (retval, orgfun, value, fn_type, outmode, nargs, p)
int retval;
rtx orgfun;
rtx value;
int no_queue;
int fn_type;
enum machine_mode outmode;
int nargs;
va_list p;
@ -3223,8 +3246,10 @@ emit_library_call_value_1 (retval, orgfun, value, no_queue, outmode, nargs, p)
#endif
#endif
if (no_queue)
if (fn_type == 1)
flags |= ECF_CONST;
else if (fn_type == 2)
flags |= ECF_PURE;
fun = orgfun;
if (libfunc_nothrow (fun))
@ -3258,7 +3283,7 @@ emit_library_call_value_1 (retval, orgfun, value, no_queue, outmode, nargs, p)
#endif
/* This call returns a big structure. */
flags &= ~ECF_CONST;
flags &= ~(ECF_CONST | ECF_PURE);
}
/* ??? Unfinished: must pass the memory address as an argument. */
@ -3282,7 +3307,7 @@ emit_library_call_value_1 (retval, orgfun, value, no_queue, outmode, nargs, p)
/* Now we are about to start emitting insns that can be deleted
if a libcall is deleted. */
if (flags & ECF_CONST)
if (flags & (ECF_CONST | ECF_PURE))
start_sequence ();
push_temp_slots ();
@ -3726,7 +3751,7 @@ emit_library_call_value_1 (retval, orgfun, value, no_queue, outmode, nargs, p)
Test valreg so we don't crash; may safely ignore `const'
if return type is void. Disable for PARALLEL return values, because
we have no way to move such values into a pseudo register. */
if ((flags & ECF_CONST)
if ((flags & (ECF_CONST | ECF_PURE))
&& valreg != 0 && GET_CODE (valreg) != PARALLEL)
{
rtx note = 0;
@ -3743,11 +3768,17 @@ emit_library_call_value_1 (retval, orgfun, value, no_queue, outmode, nargs, p)
insns = get_insns ();
end_sequence ();
if (flags & ECF_PURE)
note = gen_rtx_EXPR_LIST (VOIDmode,
gen_rtx_USE (VOIDmode,
gen_rtx_MEM (BLKmode,
gen_rtx_SCRATCH (VOIDmode))), note);
emit_libcall_block (insns, temp, valreg, note);
valreg = temp;
}
else if (flags & ECF_CONST)
else if (flags & (ECF_CONST | ECF_PURE))
{
/* Otherwise, just write out the sequence without a note. */
rtx insns = get_insns ();
@ -3830,26 +3861,18 @@ emit_library_call_value_1 (retval, orgfun, value, no_queue, outmode, nargs, p)
and machine_modes to convert them to.
The rtx values should have been passed through protect_from_queue already.
NO_QUEUE will be true if and only if the library call is a `const' call
which will be enclosed in REG_LIBCALL/REG_RETVAL notes; it is equivalent
to the flag ECF_CONST in expand_call.
NO_QUEUE must be true for const calls, because if it isn't, then
any pending increment will be emitted between REG_LIBCALL/REG_RETVAL notes,
and will be lost if the libcall sequence is optimized away.
NO_QUEUE must be false for non-const calls, because if it isn't, the
call insn will have its CONST_CALL_P bit set, and it will be incorrectly
optimized. For instance, the instruction scheduler may incorrectly
move memory references across the non-const call. */
FN_TYPE will is zero for `normal' calls, one for `const' calls, wich
which will be enclosed in REG_LIBCALL/REG_RETVAL notes and two for `pure'
calls, that are handled like `const' calls with extra
(use (memory (scratch)). */
void
emit_library_call VPARAMS((rtx orgfun, int no_queue, enum machine_mode outmode,
emit_library_call VPARAMS((rtx orgfun, int fn_type, enum machine_mode outmode,
int nargs, ...))
{
#ifndef ANSI_PROTOTYPES
rtx orgfun;
int no_queue;
int fn_type;
enum machine_mode outmode;
int nargs;
#endif
@ -3859,12 +3882,12 @@ emit_library_call VPARAMS((rtx orgfun, int no_queue, enum machine_mode outmode,
#ifndef ANSI_PROTOTYPES
orgfun = va_arg (p, rtx);
no_queue = va_arg (p, int);
fn_type = va_arg (p, int);
outmode = va_arg (p, enum machine_mode);
nargs = va_arg (p, int);
#endif
emit_library_call_value_1 (0, orgfun, NULL_RTX, no_queue, outmode, nargs, p);
emit_library_call_value_1 (0, orgfun, NULL_RTX, fn_type, outmode, nargs, p);
va_end (p);
}
@ -3878,13 +3901,13 @@ emit_library_call VPARAMS((rtx orgfun, int no_queue, enum machine_mode outmode,
If VALUE is nonzero, VALUE is returned. */
rtx
emit_library_call_value VPARAMS((rtx orgfun, rtx value, int no_queue,
emit_library_call_value VPARAMS((rtx orgfun, rtx value, int fn_type,
enum machine_mode outmode, int nargs, ...))
{
#ifndef ANSI_PROTOTYPES
rtx orgfun;
rtx value;
int no_queue;
int fn_type;
enum machine_mode outmode;
int nargs;
#endif
@ -3895,12 +3918,12 @@ emit_library_call_value VPARAMS((rtx orgfun, rtx value, int no_queue,
#ifndef ANSI_PROTOTYPES
orgfun = va_arg (p, rtx);
value = va_arg (p, rtx);
no_queue = va_arg (p, int);
fn_type = va_arg (p, int);
outmode = va_arg (p, enum machine_mode);
nargs = va_arg (p, int);
#endif
value = emit_library_call_value_1 (1, orgfun, value, no_queue, outmode, nargs, p);
value = emit_library_call_value_1 (1, orgfun, value, fn_type, outmode, nargs, p);
va_end (p);

40
gcc/extend.texi
View File

@ -1379,22 +1379,44 @@ typedef void voidfn ();
volatile voidfn fatal;
@end smallexample
@cindex @code{const} function attribute
@item const
Many functions do not examine any values except their arguments, and
have no effects except the return value. Such a function can be subject
@cindex @code{pure} function attribute
@item pure
Many functions have no effects except the return value and their
return value and depends only on the parameters and/or global variables.
Such a function can be subject
to common subexpression elimination and loop optimization just as an
arithmetic operator would be. These functions should be declared
with the attribute @code{const}. For example,
with the attribute @code{pure}. For example,
@smallexample
int square (int) __attribute__ ((const));
int square (int) __attribute__ ((pure));
@end smallexample
@noindent
says that the hypothetical function @code{square} is safe to call
fewer times than the program says.
Some of common examples of pure functions are @code{strlen} or @code{memcmp}.
Interesting non-pure functions are functions with infinite loops or those
depending on volatile memory or other system resource, that may change between
two consetuctive calls (such as @code{feof} in multithreding environment).
The attribute @code{pure} is not implemented in GNU C versions earlier
than 2.96.
@cindex @code{const} function attribute
@item const
Many functions do not examine any values except their arguments, and
have no effects except the return value. Basically this is just slightly
more strict class than the "pure" attribute above, since function is not
alloved to read global memory.
@cindex pointer arguments
Note that a function that has pointer arguments and examines the data
pointed to must @emph{not} be declared @code{const}. Likewise, a
function that calls a non-@code{const} function usually must not be
@code{const}. It does not make sense for a @code{const} function to
return @code{void}.
The attribute @code{const} is not implemented in GNU C versions earlier
than 2.5. An alternative way to declare that a function has no side
effects, which works in the current version and in some older versions,
@ -1409,12 +1431,6 @@ extern const intfn square;
This approach does not work in GNU C++ from 2.6.0 on, since the language
specifies that the @samp{const} must be attached to the return value.
@cindex pointer arguments
Note that a function that has pointer arguments and examines the data
pointed to must @emph{not} be declared @code{const}. Likewise, a
function that calls a non-@code{const} function usually must not be
@code{const}. It does not make sense for a @code{const} function to
return @code{void}.
@item format (@var{archetype}, @var{string-index}, @var{first-to-check})
@cindex @code{format} function attribute

4
gcc/optabs.c
View File

@ -3020,14 +3020,14 @@ prepare_cmp_insn (px, py, pcomparison, size, pmode, punsignedp, align,
#endif
{
#ifdef TARGET_MEM_FUNCTIONS
emit_library_call (memcmp_libfunc, 0,
emit_library_call (memcmp_libfunc, 2,
TYPE_MODE (integer_type_node), 3,
XEXP (x, 0), Pmode, XEXP (y, 0), Pmode,
convert_to_mode (TYPE_MODE (sizetype), size,
TREE_UNSIGNED (sizetype)),
TYPE_MODE (sizetype));
#else
emit_library_call (bcmp_libfunc, 0,
emit_library_call (bcmp_libfunc, 2,
TYPE_MODE (integer_type_node), 3,
XEXP (x, 0), Pmode, XEXP (y, 0), Pmode,
convert_to_mode (TYPE_MODE (integer_type_node),

5
gcc/tree.h
View File

@ -1253,6 +1253,10 @@ struct tree_type
not an alias. */
#define DECL_IS_MALLOC(NODE) (FUNCTION_DECL_CHECK (NODE)->decl.malloc_flag)
/* Nonzero in a FUNCTION_DECL means this function should be treated
as "pure" function (like const function, but may read global memory). */
#define DECL_IS_PURE(NODE) (FUNCTION_DECL_CHECK (NODE)->decl.pure_flag)
/* Nonzero in a FIELD_DECL means it is a bit field, and must be accessed
specially. */
#define DECL_BIT_FIELD(NODE) (FIELD_DECL_CHECK (NODE)->decl.bit_field_flag)
@ -1392,6 +1396,7 @@ struct tree_decl
unsigned comdat_flag : 1;
unsigned malloc_flag : 1;
unsigned no_limit_stack : 1;
unsigned pure_flag : 1;
#ifdef ONLY_INT_FIELDS
unsigned int built_in_class : 2;
#else