Unify ctf_fetch_registers and tfile_fetch_registers

Functions ctf_fetch_registers and tfile_fetch_registers have some
duplicated code about guessing the PC in regcache.  Sometimes, we
may change one function and forget to update the other one, like this
https://www.sourceware.org/ml/gdb-patches/2014-01/msg00292.html

This patch is to move the duplicated code into a new function
tracefile_fetch_registers, and let both ctf_fetch_registers and
tfile_fetch_registers call it.

gdb:

2014-04-22  Yao Qi  <yao@codesourcery.com>

	* tracefile-tfile.c (tfile_fetch_registers): Move the bottom to ...
	* tracefile.c (tracefile_fetch_registers): ... it.  New function.
	* tracefile.h (tracefile_fetch_registers): Declare.
	* ctf.c (ctf_fetch_registers): Remove the bottom.  Call
	tracefile_fetch_registers.

1 files changed, 61 insertions, 0 deletions

diff --git a/gdb/tracefile.c b/gdb/tracefile.c
index a7c3cf7..0b89cfa 100644
--- a/gdb/tracefile.c
+++ b/gdb/tracefile.c
@@ -21,6 +21,7 @@
 #include "tracefile.h"
 #include "ctf.h"
 #include "exec.h"
+#include "regcache.h"
 
 /* Helper macros.  */
 
@@ -377,6 +378,66 @@ trace_save_ctf (const char *dirname, int target_does_save)
   do_cleanups (back_to);
 }
 
+/* Fetch register data from tracefile, shared for both tfile and
+   ctf.  */
+
+void
+tracefile_fetch_registers (struct regcache *regcache, int regno)
+{
+  struct gdbarch *gdbarch = get_regcache_arch (regcache);
+  int regn, pc_regno;
+
+  /* We get here if no register data has been found.  Mark registers
+     as unavailable.  */
+  for (regn = 0; regn < gdbarch_num_regs (gdbarch); regn++)
+    regcache_raw_supply (regcache, regn, NULL);
+
+  /* We can often usefully guess that the PC is going to be the same
+     as the address of the tracepoint.  */
+  pc_regno = gdbarch_pc_regnum (gdbarch);
+
+  /* XXX This guessing code below only works if the PC register isn't
+     a pseudo-register.  The value of a pseudo-register isn't stored
+     in the (non-readonly) regcache -- instead it's recomputed
+     (probably from some other cached raw register) whenever the
+     register is read.  This guesswork should probably move to some
+     higher layer.  */
+  if (pc_regno < 0 || pc_regno >= gdbarch_num_regs (gdbarch))
+    return;
+
+  if (regno == -1 || regno == pc_regno)
+    {
+      struct tracepoint *tp = get_tracepoint (get_tracepoint_number ());
+      gdb_byte *regs;
+
+      if (tp && tp->base.loc)
+	{
+	  /* But don't try to guess if tracepoint is multi-location...  */
+	  if (tp->base.loc->next)
+	    {
+	      warning (_("Tracepoint %d has multiple "
+			 "locations, cannot infer $pc"),
+		       tp->base.number);
+	      return;
+	    }
+	  /* ... or does while-stepping.  */
+	  if (tp->step_count > 0)
+	    {
+	      warning (_("Tracepoint %d does while-stepping, "
+			 "cannot infer $pc"),
+		       tp->base.number);
+	      return;
+	    }
+
+	  regs = alloca (register_size (gdbarch, pc_regno));
+	  store_unsigned_integer (regs, register_size (gdbarch, pc_regno),
+				  gdbarch_byte_order (gdbarch),
+				  tp->base.loc->address);
+	  regcache_raw_supply (regcache, pc_regno, regs);
+	}
+    }
+}
+
 /* This is the implementation of target_ops method to_has_all_memory.  */
 
 static int