[PATCH 1/4] Remove arm_override_mode

[Yao Qi <qiyaoltc at gmail dot com>]

This patch removes global variable arm_override_mode.  The rationale is
that if the address is the next address of current pc, we can get the
thumb/arm mode from dest address computed by software single step code.

gdb:

2016-05-12  Yao Qi  <yao.qi@linaro.org>

	* arm-tdep.c: Include "gdbthread.h".
	(arm_override_mode): Remove.
	(arm_pc_is_thumb): Remove arm_override_mode.  If MEMADDR
	is the dest address of current pc, get thumb mode by dest address.
	(arm_insert_single_step_breakpoint): Remove arm_override_mode
	and cleanup.
---
 gdb/arm-tdep.c | 57 +++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 41 insertions(+), 16 deletions(-)

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 0412f71..d529481 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -55,6 +55,7 @@
 #include "elf/arm.h"
 
 #include "vec.h"
+#include "gdbthread.h"
 
 #include "record.h"
 #include "record-full.h"
@@ -143,13 +144,6 @@ static const char *const arm_mode_strings[] =
 static const char *arm_fallback_mode_string = "auto";
 static const char *arm_force_mode_string = "auto";
 
-/* Internal override of the execution mode.  -1 means no override,
-   0 means override to ARM mode, 1 means override to Thumb mode.
-   The effect is the same as if arm_force_mode has been set by the
-   user (except the internal override has precedence over a user's
-   arm_force_mode override).  */
-static int arm_override_mode = -1;
-
 /* Number of different reg name sets (options).  */
 static int num_disassembly_options;
 
@@ -422,9 +416,46 @@ arm_pc_is_thumb (struct gdbarch *gdbarch, CORE_ADDR memaddr)
   if (IS_THUMB_ADDR (memaddr))
     return 1;
 
-  /* Respect internal mode override if active.  */
-  if (arm_override_mode != -1)
-    return arm_override_mode;
+  if (target_has_execution && !is_executing (inferior_ptid))
+    {
+      gdb_byte buf[4];
+      struct regcache *regcache = get_current_regcache ();
+
+      /* Check the memory pointed by PC is readable.  */
+      if (target_read_memory (regcache_read_pc (regcache), buf, 4) == 0)
+	{
+	  struct arm_get_next_pcs next_pcs_ctx;
+	  CORE_ADDR pc;
+	  int i;
+	  VEC (CORE_ADDR) *next_pcs = NULL;
+	  struct cleanup *old_chain
+	    = make_cleanup (VEC_cleanup (CORE_ADDR), &next_pcs);
+
+	  arm_get_next_pcs_ctor (&next_pcs_ctx,
+				 &arm_get_next_pcs_ops,
+				 gdbarch_byte_order (gdbarch),
+				 gdbarch_byte_order_for_code (gdbarch),
+				 0,
+				 regcache);
+
+	  next_pcs = arm_get_next_pcs (&next_pcs_ctx);
+
+	  /* If MEMADDR is the next instruction of current pc, do the
+	     software single step computation, and get the thumb mode by
+	     the destination address.  */
+	  for (i = 0; VEC_iterate (CORE_ADDR, next_pcs, i, pc); i++)
+	    {
+	      if (UNMAKE_THUMB_ADDR (pc) == memaddr)
+		{
+		  do_cleanups (old_chain);
+
+		  return IS_THUMB_ADDR (pc);
+		}
+	    }
+
+	  do_cleanups (old_chain);
+	}
+    }
 
   /* If the user wants to override the symbol table, let him.  */
   if (strcmp (arm_force_mode_string, "arm") == 0)
@@ -4205,15 +4236,9 @@ arm_insert_single_step_breakpoint (struct gdbarch *gdbarch,
 				   struct address_space *aspace,
 				   CORE_ADDR pc)
 {
-  struct cleanup *old_chain
-    = make_cleanup_restore_integer (&arm_override_mode);
-
-  arm_override_mode = IS_THUMB_ADDR (pc);
   pc = gdbarch_addr_bits_remove (gdbarch, pc);
 
   insert_single_step_breakpoint (gdbarch, aspace, pc);
-
-  do_cleanups (old_chain);
 }
 
 /* Given BUF, which is OLD_LEN bytes ending at ENDADDR, expand
-- 
1.9.1