regcache is used in many places in gdb in different ways, so regcache
becomes a flat and fat object. That exposes some unnecessary APIs to
different part, and some APIs are misused or abused:
1) gdbarch methods pseudo_register_read, pseudo_register_read_value,
read_pc have a parameter 'regcache *', but these two gdbarch methods
only need raw_read* and cooked_read* methods. So it is better to
pass a class which only has raw_read* and cooked_read* methods, and
other regcache methods are invisible to each gdbarch implementation.
2) target_ops methods to_fetch_registers and to_store_registers have a
parameter 'regcache *', but these two target_ops methods only need
raw_supply and raw_collect methods, because raw registers are from
target
layer, pseudo registers are "composed" or "created" by gdbarch.
3) jit.c uses regcache in an odd way, and record-full.c should use
a simple version regcache instead of an array (see patch 11)
Beside these api issues, one issue in regcache is that there is no
type or class for readonly regcache. We use a flag field m_readonly_p
to indicate the regcache is readonly or not, so some regcache apis have
assert that this regcache is or is not readonly. The better way to do
this is to create a new class for readonly regcache which doesn't have
write methods at all.
This patch series fixes all of the problems above except 2) (I had a
patch to fix 2 in my tree, but still need more time to polish it.) by
designing a class hierarchy about regcache, like this,
reg_buffer
^
|
------+-----
^
|
readable_regcache
^
|
------+------
^ ^
| |
detached_regcache readonly_detached_regcache
^
|
regcache
Class reg_buffer is a simple class, having register contents and status
(in patch 1). readable_regcache is an abstract class only having
raw_read*
and cooked_read* methods (in patch 2). detached_regcache is a class
which
has read and write methods, but it detaches from target, IOW, the
write doesn't go through. Class readonly_detached_regcache is the
readonly
regcache, created from regcache::save method.
This is the v2 of this patch series, v1 can be found
https://sourceware.org/ml/gdb-patches/2017-12/msg00014.html Some
changes compared with v1,
- Some of the preparatory patches in v1 are already committed,
- Rename some classes,
- Pass readable_regcache to gdbarch read_pc. We can pass
readable_regcache
to gdbarch breakpoint_kind_from_current_state as well, because this
gdbarch method doesn't need to write regcache. The reason I don't
that is arm_breakpoint_kind_from_current_state uses a function
arm_get_next_pcs_ctor shared between GDB and GDBserver, and I don't
propagate the regcache changes to GDBserver at this moment,
This patch series is pushed to users/qiyao/regcache-split-4-2.
Regression
tested on {x86_64,aarch64}-linux.