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[PATCH] Fix returning floating points values for x86
- To: gdb-patches at sources dot redhat dot com
- Subject: [PATCH] Fix returning floating points values for x86
- From: Mark Kettenis <kettenis at wins dot uva dot nl>
- Date: Wed, 11 Jul 2001 10:49:16 +0200
- CC: grossman at juniper dot dot dot net
Fixes two FAILS in gdb.base/return2.exp.
Stu, I was about to commit this patch when I saw you FreeBSD patch.
Patch is almost identical (modulo comments), so it must be right :-).
I nevertheless took all the credit ;-). I will come back to you on
some of the other stuff in your patch.
Checked in.
Mark
Index: ChangeLog
from Mark Kettenis <kettenis@gnu.org>
* i386-tdep.c (i386_extract_return_value): "Fix" comment.
(i386_store_return_value): Frob FPU status and tag word to make
sure the return value is the only value on the FPU stack.
Index: i386-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.c,v
retrieving revision 1.31
diff -u -p -r1.31 i386-tdep.c
--- i386-tdep.c 2001/05/09 16:16:33 1.31
+++ i386-tdep.c 2001/07/11 08:38:27
@@ -803,7 +803,8 @@ i386_extract_return_value (struct type *
return;
}
- /* Floating-point return values can be found in %st(0). */
+ /* Floating-point return values can be found in %st(0).
+ FIXME: Does %st(0) always correspond to FP0? */
if (len == TARGET_LONG_DOUBLE_BIT / TARGET_CHAR_BIT
&& TARGET_LONG_DOUBLE_FORMAT == &floatformat_i387_ext)
{
@@ -861,6 +862,8 @@ i386_store_return_value (struct type *ty
if (TYPE_CODE (type) == TYPE_CODE_FLT)
{
+ unsigned int fstat;
+
if (NUM_FREGS == 0)
{
warning ("Cannot set floating-point return value.");
@@ -889,6 +892,16 @@ i386_store_return_value (struct type *ty
write_register_bytes (REGISTER_BYTE (FP0_REGNUM), buf,
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? */
+ fstat = read_register (FSTAT_REGNUM);
+ fstat |= (7 << 11);
+ write_register (FSTAT_REGNUM, fstat);
+
+ /* Mark %st(1) through %st(7) as empty. */
+ write_register (FTAG_REGNUM, 0x3fff);
}
else
{