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Re: Setting an SSE register to a certain value
- From: Eli Zaretskii <eliz at gnu dot org>
- To: Guillaume POIRIER <poirierg at gmail dot com>
- Cc: gdb-patches at sources dot redhat dot com
- Date: Wed, 28 Dec 2005 22:07:40 +0200
- Subject: Re: Setting an SSE register to a certain value
- References: <4e03026a0512270816p2ea883cfj42934c557ec7f4a5@mail.gmail.com> <8f2776cb0512271615g54aa91a4t3bc89777105d33b7@mail.gmail.com> <uoe31u9zj.fsf@gnu.org> <4e03026a0512280015m39499343rf96f8075fad23eeb@mail.gmail.com>
- Reply-to: Eli Zaretskii <eliz at gnu dot org>
> Date: Wed, 28 Dec 2005 09:15:45 +0100
> From: Guillaume POIRIER <poirierg@gmail.com>
>
> > That is, try this:
> >
> > set $xmm2.uint128 = 0x000000000000000000000000FFFFFFFF
>
> Thanks you so much! That worked beautifully. I hope this information
> can be added to your documentation as this will probably come in handy
> to other people, don't you think? :-)
Yes, I've just added the following to the manual:
2005-12-28 Eli Zaretskii <eliz@gnu.org>
* gdb.texinfo (Registers): Describe how to refer to SSE and MMX
registers and the likes.
Index: gdb/doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.302
diff -u -r1.302 gdb.texinfo
--- gdb/doc/gdb.texinfo 24 Dec 2005 15:28:44 -0000 1.302
+++ gdb/doc/gdb.texinfo 28 Dec 2005 20:04:30 -0000
@@ -6279,6 +6279,36 @@
that makes sense for your program), but the @code{info registers} command
prints the data in both formats.
+@cindex SSE registers (x86)
+@cindex MMX registers (x86)
+Some machines have special registers whose contents can be interpreted
+in several different ways. For example, modern x86-based machines
+have SSE and MMX registers that can hold several values packed
+together in several different formats. @value{GDBN} refers to such
+registers in @code{struct} notation:
+
+@smallexample
+(@value{GDBP}) print $xmm1
+$1 = @{
+ v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
+ v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
+ v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
+ v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
+ v4_int32 = @{0, 20657912, 11, 13@},
+ v2_int64 = @{88725056443645952, 55834574859@},
+ uint128 = 0x0000000d0000000b013b36f800000000
+@}
+@end smallexample
+
+@noindent
+To set values of such registers, you need to tell @value{GDBN} which
+view of the register you wish to change, as if you were assigning
+value to a @code{struct} member:
+
+@smallexample
+ (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
+@end smallexample
+
Normally, register values are relative to the selected stack frame
(@pxref{Selection, ,Selecting a frame}). This means that you get the
value that the register would contain if all stack frames farther in