[binutils-gdb] Remove some unnecessary inferior_ptid setting/restoring when fetching/storing registers

[Simon Marchi <simark at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3e00d44febb8093d8dc0e6842b975afb194c4fd1

commit 3e00d44febb8093d8dc0e6842b975afb194c4fd1
Author: Simon Marchi <simon.marchi@ericsson.com>
Date:   Thu Mar 23 13:37:06 2017 -0400

    Remove some unnecessary inferior_ptid setting/restoring when fetching/storing registers
    
    Now that the to_fetch_registers, to_store_registers and
    to_prepare_to_store target methods don't rely on the value of
    inferior_ptid anymore, we can remove a bunch of now unnecessary setting
    and restoring of inferior_ptid.
    
    The asserts added recently in target_fetch_registers and
    target_store_registers, which validate that inferior_ptid matches the
    regcache's ptid, must go away.  It's the whole point of this effort, to
    not require inferior_ptid to have a particular value when calling these
    functions.
    
    One thing that I noticed is how sol-thread.c's ps_lgetregs and friends
    use the current value of inferior_ptid instead of what's passed as
    argument (ph->ptid), unlike proc-service.c's versions of the same
    functions.  Is it expected?  I left it like this in the current patch,
    but unless there's a good reason for it to be that way, I guess we
    should make it use the parameter.
    
    gdb/ChangeLog:
    
    	* fbsd-tdep.c (fbsd_corefile_thread): Don't set/restore
    	inferior_ptid.
    	* proc-service.c (ps_lgetregs, ps_lsetregs, ps_lgetfpregs,
    	ps_lsetfpregs): Likewise.
    	* regcache.c (regcache_raw_update, regcache_raw_write): Likewise.
    	* sol-thread.c (ps_lgetregs, ps_lsetregs, ps_lgetfpregs,
    	ps_lsetfpregs): Likewise.
    	* target.c (target_fetch_registers, target_store_registers):
    	Remove asserts.

Diff:
---
 gdb/ChangeLog      | 12 ++++++++++++
 gdb/fbsd-tdep.c    |  4 ----
 gdb/proc-service.c | 36 ++++++++++++------------------------
 gdb/regcache.c     | 17 +++--------------
 gdb/sol-thread.c   | 48 ++++++++++++------------------------------------
 gdb/target.c       |  4 ----
 6 files changed, 39 insertions(+), 82 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a3f503d..5ad7ac3 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,15 @@
+2017-03-23  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* fbsd-tdep.c (fbsd_corefile_thread): Don't set/restore
+	inferior_ptid.
+	* proc-service.c (ps_lgetregs, ps_lsetregs, ps_lgetfpregs,
+	ps_lsetfpregs): Likewise.
+	* regcache.c (regcache_raw_update, regcache_raw_write): Likewise.
+	* sol-thread.c (ps_lgetregs, ps_lsetregs, ps_lgetfpregs,
+	ps_lsetfpregs): Likewise.
+	* target.c (target_fetch_registers, target_store_registers):
+	Remove asserts.
+
 2017-03-23  Alan Hayward  <alan.hayward@arm.com>
 
 	* sol-thread.c (sol_thread_store_registers): Remove regcache calls.
diff --git a/gdb/fbsd-tdep.c b/gdb/fbsd-tdep.c
index e757910..46875d8 100644
--- a/gdb/fbsd-tdep.c
+++ b/gdb/fbsd-tdep.c
@@ -193,15 +193,11 @@ static void
 fbsd_corefile_thread (struct thread_info *info,
 		      struct fbsd_corefile_thread_data *args)
 {
-  struct cleanup *old_chain;
   struct regcache *regcache;
 
   regcache = get_thread_arch_regcache (info->ptid, args->gdbarch);
 
-  old_chain = save_inferior_ptid ();
-  inferior_ptid = info->ptid;
   target_fetch_registers (regcache, -1);
-  do_cleanups (old_chain);
 
   args->note_data = fbsd_collect_thread_registers
     (regcache, info->ptid, args->obfd, args->note_data,
diff --git a/gdb/proc-service.c b/gdb/proc-service.c
index d39830c..415ba0a 100644
--- a/gdb/proc-service.c
+++ b/gdb/proc-service.c
@@ -158,16 +158,13 @@ ps_pdwrite (gdb_ps_prochandle_t ph, psaddr_t addr,
 ps_err_e
 ps_lgetregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, prgregset_t gregset)
 {
-  struct cleanup *old_chain = save_inferior_ptid ();
-  struct regcache *regcache;
-
-  inferior_ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   target_fetch_registers (regcache, -1);
   fill_gregset (regcache, (gdb_gregset_t *) gregset, -1);
 
-  do_cleanups (old_chain);
   return PS_OK;
 }
 
@@ -177,16 +174,13 @@ ps_lgetregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, prgregset_t gregset)
 ps_err_e
 ps_lsetregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, const prgregset_t gregset)
 {
-  struct cleanup *old_chain = save_inferior_ptid ();
-  struct regcache *regcache;
-
-  inferior_ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   supply_gregset (regcache, (const gdb_gregset_t *) gregset);
   target_store_registers (regcache, -1);
 
-  do_cleanups (old_chain);
   return PS_OK;
 }
 
@@ -197,16 +191,13 @@ ps_err_e
 ps_lgetfpregs (gdb_ps_prochandle_t ph, lwpid_t lwpid,
 	       gdb_prfpregset_t *fpregset)
 {
-  struct cleanup *old_chain = save_inferior_ptid ();
-  struct regcache *regcache;
-
-  inferior_ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   target_fetch_registers (regcache, -1);
   fill_fpregset (regcache, (gdb_fpregset_t *) fpregset, -1);
 
-  do_cleanups (old_chain);
   return PS_OK;
 }
 
@@ -217,16 +208,13 @@ ps_err_e
 ps_lsetfpregs (gdb_ps_prochandle_t ph, lwpid_t lwpid,
 	       const gdb_prfpregset_t *fpregset)
 {
-  struct cleanup *old_chain = save_inferior_ptid ();
-  struct regcache *regcache;
-
-  inferior_ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (ph->ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   supply_fpregset (regcache, (const gdb_fpregset_t *) fpregset);
   target_store_registers (regcache, -1);
 
-  do_cleanups (old_chain);
   return PS_OK;
 }
 
diff --git a/gdb/regcache.c b/gdb/regcache.c
index 58d4f56..71223a1 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -666,11 +666,7 @@ regcache_raw_update (struct regcache *regcache, int regnum)
   if (!regcache->readonly_p
       && regcache_register_status (regcache, regnum) == REG_UNKNOWN)
     {
-      struct cleanup *old_chain = save_inferior_ptid ();
-
-      inferior_ptid = regcache->ptid;
       target_fetch_registers (regcache, regnum);
-      do_cleanups (old_chain);
 
       /* A number of targets can't access the whole set of raw
 	 registers (because the debug API provides no means to get at
@@ -937,8 +933,7 @@ void
 regcache_raw_write (struct regcache *regcache, int regnum,
 		    const gdb_byte *buf)
 {
-  struct cleanup *chain_before_save_inferior;
-  struct cleanup *chain_before_invalidate_register;
+  struct cleanup *old_chain;
 
   gdb_assert (regcache != NULL && buf != NULL);
   gdb_assert (regnum >= 0 && regnum < regcache->descr->nr_raw_registers);
@@ -956,24 +951,18 @@ regcache_raw_write (struct regcache *regcache, int regnum,
 		  regcache->descr->sizeof_register[regnum]) == 0))
     return;
 
-  chain_before_save_inferior = save_inferior_ptid ();
-  inferior_ptid = regcache->ptid;
-
   target_prepare_to_store (regcache);
   regcache_raw_set_cached_value (regcache, regnum, buf);
 
   /* Register a cleanup function for invalidating the register after it is
      written, in case of a failure.  */
-  chain_before_invalidate_register
-    = make_cleanup_regcache_invalidate (regcache, regnum);
+  old_chain = make_cleanup_regcache_invalidate (regcache, regnum);
 
   target_store_registers (regcache, regnum);
 
   /* The target did not throw an error so we can discard invalidating the
      register and restore the cleanup chain to what it was.  */
-  discard_cleanups (chain_before_invalidate_register);
-
-  do_cleanups (chain_before_save_inferior);
+  discard_cleanups (old_chain);
 }
 
 void
diff --git a/gdb/sol-thread.c b/gdb/sol-thread.c
index e59c0cb..7c1620a 100644
--- a/gdb/sol-thread.c
+++ b/gdb/sol-thread.c
@@ -872,19 +872,13 @@ ps_ptwrite (gdb_ps_prochandle_t ph, gdb_ps_addr_t addr,
 ps_err_e
 ps_lgetregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, prgregset_t gregset)
 {
-  struct cleanup *old_chain;
-  struct regcache *regcache;
-
-  old_chain = save_inferior_ptid ();
-
-  inferior_ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   target_fetch_registers (regcache, -1);
   fill_gregset (regcache, (gdb_gregset_t *) gregset, -1);
 
-  do_cleanups (old_chain);
-
   return PS_OK;
 }
 
@@ -894,19 +888,13 @@ ps_err_e
 ps_lsetregs (gdb_ps_prochandle_t ph, lwpid_t lwpid,
 	     const prgregset_t gregset)
 {
-  struct cleanup *old_chain;
-  struct regcache *regcache;
-
-  old_chain = save_inferior_ptid ();
-
-  inferior_ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   supply_gregset (regcache, (const gdb_gregset_t *) gregset);
   target_store_registers (regcache, -1);
 
-  do_cleanups (old_chain);
-
   return PS_OK;
 }
 
@@ -952,19 +940,13 @@ ps_err_e
 ps_lgetfpregs (gdb_ps_prochandle_t ph, lwpid_t lwpid,
 	       prfpregset_t *fpregset)
 {
-  struct cleanup *old_chain;
-  struct regcache *regcache;
-
-  old_chain = save_inferior_ptid ();
-
-  inferior_ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   target_fetch_registers (regcache, -1);
   fill_fpregset (regcache, (gdb_fpregset_t *) fpregset, -1);
 
-  do_cleanups (old_chain);
-
   return PS_OK;
 }
 
@@ -974,19 +956,13 @@ ps_err_e
 ps_lsetfpregs (gdb_ps_prochandle_t ph, lwpid_t lwpid,
 	       const prfpregset_t * fpregset)
 {
-  struct cleanup *old_chain;
-  struct regcache *regcache;
-
-  old_chain = save_inferior_ptid ();
-
-  inferior_ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
-  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
+  ptid_t ptid = ptid_build (ptid_get_pid (inferior_ptid), lwpid, 0);
+  struct regcache *regcache
+    = get_thread_arch_regcache (ptid, target_gdbarch ());
 
   supply_fpregset (regcache, (const gdb_fpregset_t *) fpregset);
   target_store_registers (regcache, -1);
 
-  do_cleanups (old_chain);
-
   return PS_OK;
 }
 
diff --git a/gdb/target.c b/gdb/target.c
index 359bf0d..0ff8515 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -3587,8 +3587,6 @@ debug_print_register (const char * func,
 void
 target_fetch_registers (struct regcache *regcache, int regno)
 {
-  gdb_assert (ptid_equal (regcache_get_ptid (regcache), inferior_ptid));
-
   current_target.to_fetch_registers (&current_target, regcache, regno);
   if (targetdebug)
     debug_print_register ("target_fetch_registers", regcache, regno);
@@ -3600,8 +3598,6 @@ target_store_registers (struct regcache *regcache, int regno)
   if (!may_write_registers)
     error (_("Writing to registers is not allowed (regno %d)"), regno);
 
-  gdb_assert (ptid_equal (regcache_get_ptid (regcache), inferior_ptid));
-
   current_target.to_store_registers (&current_target, regcache, regno);
   if (targetdebug)
     {