[v2] gdb.trace: Fix string collection for 64-bit platforms.
Commit Message
String collection always used ref32 to fetch the string pointer. Make it
use gen_fetch instead.
As a side effect, this patch changes dup+const+trace+pop sequence used
for collecting the string's address to a trace_quick opcode. This
results in a shorter agent expression.
This appeared to work on x86_64 since it's a little-endian platform, and
malloc (used in gdb.trace/collection.exp) returns addresses in low 4GB.
Noticed and tested on s390x-ibm-linux-gnu, also tested on
i686-unknown-linux-gnu and x86_64-unknown-linux-gnu.
gdb/ChangeLog:
* ax-gdb.c (gen_traced_pop): Use gen_fetch for string collection.
---
Instead of factoring out the switch, I just delegated to gen_fetch.
Turns out we can shave off a few ops this way, too. Likewise tested
on s390, s390x, i686, x86_64.
gdb/ChangeLog | 4 ++++
gdb/ax-gdb.c | 23 +++++++++++------------
2 files changed, 15 insertions(+), 12 deletions(-)
Comments
On 01/21/2016 04:43 PM, Marcin Kościelnicki wrote:
> String collection always used ref32 to fetch the string pointer. Make it
> use gen_fetch instead.
>
> As a side effect, this patch changes dup+const+trace+pop sequence used
> for collecting the string's address to a trace_quick opcode. This
> results in a shorter agent expression.
>
> This appeared to work on x86_64 since it's a little-endian platform, and
> malloc (used in gdb.trace/collection.exp) returns addresses in low 4GB.
> Noticed and tested on s390x-ibm-linux-gnu, also tested on
> i686-unknown-linux-gnu and x86_64-unknown-linux-gnu.
>
> gdb/ChangeLog:
>
> * ax-gdb.c (gen_traced_pop): Use gen_fetch for string collection.
> ---
> Instead of factoring out the switch, I just delegated to gen_fetch.
> Turns out we can shave off a few ops this way, too. Likewise tested
> on s390, s390x, i686, x86_64.
Even better. This is OK.
Thanks,
Pedro Alves
On 21/01/16 17:55, Pedro Alves wrote:
> On 01/21/2016 04:43 PM, Marcin Kościelnicki wrote:
>> String collection always used ref32 to fetch the string pointer. Make it
>> use gen_fetch instead.
>>
>> As a side effect, this patch changes dup+const+trace+pop sequence used
>> for collecting the string's address to a trace_quick opcode. This
>> results in a shorter agent expression.
>>
>> This appeared to work on x86_64 since it's a little-endian platform, and
>> malloc (used in gdb.trace/collection.exp) returns addresses in low 4GB.
>> Noticed and tested on s390x-ibm-linux-gnu, also tested on
>> i686-unknown-linux-gnu and x86_64-unknown-linux-gnu.
>>
>> gdb/ChangeLog:
>>
>> * ax-gdb.c (gen_traced_pop): Use gen_fetch for string collection.
>> ---
>> Instead of factoring out the switch, I just delegated to gen_fetch.
>> Turns out we can shave off a few ops this way, too. Likewise tested
>> on s390, s390x, i686, x86_64.
>
> Even better. This is OK.
>
> Thanks,
> Pedro Alves
>
Thanks, pushed.
@@ -1,3 +1,7 @@
+2016-01-21 Marcin Kościelnicki <koriakin@0x04.net>
+
+ * ax-gdb.c (gen_traced_pop): Use gen_fetch for string collection.
+
2016-01-21 Andrew Burgess <andrew.burgess@embecosm.com>
* disasm.c (maybe_add_dis_line_entry): Rename to...
@@ -394,26 +394,25 @@ gen_traced_pop (struct gdbarch *gdbarch,
case axs_lvalue_memory:
{
- if (string_trace)
- ax_simple (ax, aop_dup);
-
/* Initialize the TYPE_LENGTH if it is a typedef. */
check_typedef (value->type);
- /* There's no point in trying to use a trace_quick bytecode
- here, since "trace_quick SIZE pop" is three bytes, whereas
- "const8 SIZE trace" is also three bytes, does the same
- thing, and the simplest code which generates that will also
- work correctly for objects with large sizes. */
- ax_const_l (ax, TYPE_LENGTH (value->type));
- ax_simple (ax, aop_trace);
-
if (string_trace)
{
- ax_simple (ax, aop_ref32);
+ gen_fetch (ax, value->type);
ax_const_l (ax, ax->trace_string);
ax_simple (ax, aop_tracenz);
}
+ else
+ {
+ /* There's no point in trying to use a trace_quick bytecode
+ here, since "trace_quick SIZE pop" is three bytes, whereas
+ "const8 SIZE trace" is also three bytes, does the same
+ thing, and the simplest code which generates that will also
+ work correctly for objects with large sizes. */
+ ax_const_l (ax, TYPE_LENGTH (value->type));
+ ax_simple (ax, aop_trace);
+ }
}
break;