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Here is an explanation of implicit calls to library routines.
This macro, if defined, should expand to a piece of C code that will get expanded when compiling functions for libgcc.a. It can be used to provide alternate names for GCC’s internal library functions if there are ABI-mandated names that the compiler should provide.
This hook should declare additional library routines or rename
existing ones, using the functions set_optab_libfunc
and
init_one_libfunc
defined in optabs.c.
init_optabs
calls this macro after initializing all the normal
library routines.
The default is to do nothing. Most ports don’t need to define this hook.
If false (the default), internal library routines start with two
underscores. If set to true, these routines start with __gnu_
instead. E.g., __muldi3
changes to __gnu_muldi3
. This
currently only affects functions defined in libgcc2.c. If this
is set to true, the tm.h file must also
#define LIBGCC2_GNU_PREFIX
.
This macro should return true
if the library routine that
implements the floating point comparison operator comparison in
mode mode will return a boolean, and false if it will
return a tristate.
GCC’s own floating point libraries return tristates from the comparison operators, so the default returns false always. Most ports don’t need to define this macro.
This macro should evaluate to true
if the integer comparison
functions (like __cmpdi2
) return 0 to indicate that the first
operand is smaller than the second, 1 to indicate that they are equal,
and 2 to indicate that the first operand is greater than the second.
If this macro evaluates to false
the comparison functions return
-1, 0, and 1 instead of 0, 1, and 2. If the target uses the routines
in libgcc.a, you do not need to define this macro.
The value of EDOM
on the target machine, as a C integer constant
expression. If you don’t define this macro, GCC does not attempt to
deposit the value of EDOM
into errno
directly. Look in
/usr/include/errno.h to find the value of EDOM
on your
system.
If you do not define TARGET_EDOM
, then compiled code reports
domain errors by calling the library function and letting it report the
error. If mathematical functions on your system use matherr
when
there is an error, then you should leave TARGET_EDOM
undefined so
that matherr
is used normally.
Define this macro as a C expression to create an rtl expression that
refers to the global “variable” errno
. (On certain systems,
errno
may not actually be a variable.) If you don’t define this
macro, a reasonable default is used.
When this macro is nonzero, GCC will implicitly optimize sin
calls into
sinf
and similarly for other functions defined by C99 standard. The
default is zero because a number of existing systems lack support for these
functions in their runtime so this macro needs to be redefined to one on
systems that do support the C99 runtime.
When this macro is nonzero, GCC will implicitly optimize calls to sin
and cos
with the same argument to a call to sincos
. The
default is zero. The target has to provide the following functions:
void sincos(double x, double *sin, double *cos); void sincosf(float x, float *sin, float *cos); void sincosl(long double x, long double *sin, long double *cos);
Set this macro to 1 to use the "NeXT" Objective-C message sending conventions by default. This calling convention involves passing the object, the selector and the method arguments all at once to the method-lookup library function. This is the usual setting when targeting Darwin/Mac OS X systems, which have the NeXT runtime installed.
If the macro is set to 0, the "GNU" Objective-C message sending convention will be used by default. This convention passes just the object and the selector to the method-lookup function, which returns a pointer to the method.
In either case, it remains possible to select code-generation for the alternate scheme, by means of compiler command line switches.
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