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| author | Mark Kettenis <kettenis@gnu.org> | 2001-07-12 18:50:01 +0000 |
|---|---|---|
| committer | Mark Kettenis <kettenis@gnu.org> | 2001-07-12 18:50:01 +0000 |
| commit | 635b0cc19c737fb6706bc639c6373c0a8f36afe2 (patch) | |
| tree | 4cad807eea91cc0ef8dd77746d44c838ae0d8896 | |
| parent | 1e4fac5928dd643e538e672ea234e82b7a733c0d (diff) | |
| download | gdb-635b0cc19c737fb6706bc639c6373c0a8f36afe2.zip gdb-635b0cc19c737fb6706bc639c6373c0a8f36afe2.tar.gz gdb-635b0cc19c737fb6706bc639c6373c0a8f36afe2.tar.bz2 | |
* 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.
| -rw-r--r-- | gdb/ChangeLog | 5 | ||||
| -rw-r--r-- | gdb/i386-tdep.c | 21 |
2 files changed, 18 insertions, 8 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 64f6cf5..95ea9a0 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -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): diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c index 108a707..b7d5a17 100644 --- a/gdb/i386-tdep.c +++ b/gdb/i386-tdep.c @@ -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 |