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* i386-tdep.c (i386_extract_return_value): Undo 2001-07-11 changes

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to comment.
(i386_store_return_value): Improve comments about storing
floating-point return values.
This commit is contained in:
Mark Kettenis 2001-07-12 18:50:01 +00:00
parent 1e4fac5928
commit 635b0cc19c
2 changed files with 18 additions and 8 deletions
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5
gdb/ChangeLog
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@ -1,5 +1,10 @@
2001-07-12 Mark Kettenis <kettenis@gnu.org>
* i386-tdep.c (i386_extract_return_value): Undo 2001-07-11 changes
to comment.
(i386_store_return_value): Improve comments about storing
floating-point return values.
* config/arm/xm-linux.h, config/i386/xm-linux.h,
config/m68k/xm-linux.h, config/powerpc/xm-linux.h,
config/sparc/xm-linux.h, config/ia64/xm-linux.h (HAVE_TERMIOS):

21
gdb/i386-tdep.c
View file

@ -803,8 +803,7 @@ i386_extract_return_value (struct type *type, char *regbuf, char *valbuf)
return;
}
/* Floating-point return values can be found in %st(0).
FIXME: Does %st(0) always correspond to FP0? */
/* Floating-point return values can be found in %st(0). */
if (len == TARGET_LONG_DOUBLE_BIT / TARGET_CHAR_BIT
&& TARGET_LONG_DOUBLE_FORMAT == &floatformat_i387_ext)
{
@ -870,7 +869,10 @@ i386_store_return_value (struct type *type, char *valbuf)
return;
}
/* Floating-point return values can be found in %st(0). */
/* Returning floating-point values is a bit tricky. Apart from
storing the return value in %st(0), we have to simulate the
state of the FPU at function return point. */
if (len == TARGET_LONG_DOUBLE_BIT / TARGET_CHAR_BIT
&& TARGET_LONG_DOUBLE_FORMAT == &floatformat_i387_ext)
{
@ -884,7 +886,7 @@ i386_store_return_value (struct type *type, char *valbuf)
DOUBLEST val;
/* Convert the value found in VALBUF to the extended
floating point format used by the FPU. This is probably
floating-point format used by the FPU. This is probably
not exactly how it would happen on the target itself, but
it is the best we can do. */
val = extract_floating (valbuf, TYPE_LENGTH (type));
@ -893,14 +895,17 @@ i386_store_return_value (struct type *type, char *valbuf)
FPU_REG_RAW_SIZE);
}
/* Set the top of the floating point register stack to 7. That
makes sure that FP0 (which we set above) is indeed %st(0).
FIXME: Perhaps we should completely reset the status word? */
/* Set the top of the floating-point register stack to 7. The
actual value doesn't really matter, but 7 is what a normal
function return would end up with if the program started out
with a freshly initialized FPU. */
fstat = read_register (FSTAT_REGNUM);
fstat |= (7 << 11);
write_register (FSTAT_REGNUM, fstat);
/* Mark %st(1) through %st(7) as empty. */
/* Mark %st(1) through %st(7) as empty. Since we set the top of
the floating-point register stack to 7, the appropriate value
for the tag word is 0x3fff. */
write_register (FTAG_REGNUM, 0x3fff);
}
else