[PATCH 08/10] Don't invalidate dcache when option stack-cache is changed

Yao Qi
2013-11-03T05:56:05Z

Nowadays, option "stack-cache" on->off and off->on transitions trigger
cache invalidation. It is not very necessary and not friendly to
using target_dcache for other purpose, such as code caching.

Option "stack-cache" can be regarded as a switch, to decide whether to
read through cache when reading data from target. When this switch is
off, read from target. When the switch is on, read from cache. We
need to keep cache in sync, so when GDB writes data, cache should be
updated unconditionally.

gdb:

2013-11-02 Yao Qi <yao@codesourcery.com>

* target-dcache.c (stack_cache_enabled_p_1): Remove.
(set_stack_cache_enabled_p): Remove.
(_initialize_target_dcache): Update command register.
* target.c (memory_xfer_partial_1): Don't check
stack_cache_enabled.
---
gdb/target-dcache.c | 24 ++++--------------------
gdb/target.c | 4 ++--
2 files changed, 6 insertions(+), 22 deletions(-)

diff --git a/gdb/target-dcache.c b/gdb/target-dcache.c
index a840c40..ce36bbb 100644
--- a/gdb/target-dcache.c
+++ b/gdb/target-dcache.c
@@ -100,26 +100,10 @@ target_dcache_get_or_init (void)
}

/* The option sets this. */
-static int stack_cache_enabled_p_1 = 1;
-/* And set_stack_cache_enabled_p updates this.
- The reason for the separation is so that we don't flush the cache for
- on->on transitions. */
-static int stack_cache_enabled_p = 1;
-
-/* This is called *after* the stack-cache has been set.
- Flush the cache for off->on and on->off transitions.
- There's no real need to flush the cache for on->off transitions,
- except cleanliness. */

-static void
-set_stack_cache_enabled_p (char *args, int from_tty,
- struct cmd_list_element *c)
-{
- if (stack_cache_enabled_p != stack_cache_enabled_p_1)
- target_dcache_invalidate ();
+static int stack_cache_enabled_p = 1;

- stack_cache_enabled_p = stack_cache_enabled_p_1;
-}
+/* Show option "stack-cache". */

static void
show_stack_cache_enabled_p (struct ui_file *file, int from_tty,
@@ -143,13 +127,13 @@ void
_initialize_target_dcache (void)
{
add_setshow_boolean_cmd ("stack-cache", class_support,
- &stack_cache_enabled_p_1, _("\
+ &stack_cache_enabled_p, _("\
Set cache use for stack access."), _("\
Show cache use for stack access."), _("\
When on, use the data cache for all stack access, regardless of any\n\
configured memory regions. This improves remote performance significantly.\n\
By default, caching for stack access is on."),
- set_stack_cache_enabled_p,
+ NULL,
show_stack_cache_enabled_p,
&setlist, &showlist);

diff --git a/gdb/target.c b/gdb/target.c
index 1212347..55c5d78 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -1593,14 +1593,14 @@ memory_xfer_partial_1 (struct target_ops *ops, enum target_object object,

/* Make sure the cache gets updated no matter what - if we are writing
to the stack. Even if this write is not tagged as such, we still need
- to update the cache. */
+ to update the cache. Update the cache to keep it in sync if it
+ has been initialized. */

if (res > 0
&& inf != NULL
&& writebuf != NULL
&& target_dcache_init_p ()
&& !region->attrib.cache
- && stack_cache_enabled ()
&& object != TARGET_OBJECT_STACK_MEMORY)
{
DCACHE *dcache = target_dcache_get ();
--
1.7.7.6