Add support for reading frame registers to Python API.

The ability to read registers is needed to use Frame Filter API to
display the frames created by JIT compilers.

gdb/ChangeLog:

2014-08-29  Sasha Smundak  <asmundak@google.com>

	* python/py-frame.c (frapy_read_register): New function.

gdb/doc/ChangeLog:

2014-08-26  Sasha Smundak  <asmundak@google.com>

	* python.texi (Frames in Python): Add read_register description.

gdb/testsuite/ChangeLog:

2014-08-26  Sasha Smundak  <asmundak@google.com>

	* gdb.python/py-frame.exp: Test Frame.read_register.

1 files changed, 38 insertions, 0 deletions

diff --git a/gdb/python/py-frame.c b/gdb/python/py-frame.c
index 120e147..859d115 100644
--- a/gdb/python/py-frame.c
+++ b/gdb/python/py-frame.c
@@ -28,6 +28,7 @@
 #include "python-internal.h"
 #include "symfile.h"
 #include "objfiles.h"
+#include "user-regs.h"
 
 typedef struct {
   PyObject_HEAD
@@ -235,6 +236,40 @@ frapy_pc (PyObject *self, PyObject *args)
   return gdb_py_long_from_ulongest (pc);
 }
 
+/* Implementation of gdb.Frame.read_register (self, register) -> gdb.Value.
+   Returns the value of a register in this frame.  */
+
+static PyObject *
+frapy_read_register (PyObject *self, PyObject *args)
+{
+  volatile struct gdb_exception except;
+  const char *regnum_str;
+  struct value *val = NULL;
+
+  if (!PyArg_ParseTuple (args, "s", &regnum_str))
+    return NULL;
+
+  TRY_CATCH (except, RETURN_MASK_ALL)
+    {
+      struct frame_info *frame;
+      int regnum;
+
+      FRAPY_REQUIRE_VALID (self, frame);
+
+      regnum = user_reg_map_name_to_regnum (get_frame_arch (frame),
+                                            regnum_str,
+                                            strlen (regnum_str));
+      if (regnum >= 0)
+        val = value_of_register (regnum, frame);
+
+      if (val == NULL)
+        PyErr_SetString (PyExc_ValueError, _("Unknown register."));
+    }
+  GDB_PY_HANDLE_EXCEPTION (except);
+
+  return val == NULL ? NULL : value_to_value_object (val);
+}
+
 /* Implementation of gdb.Frame.block (self) -> gdb.Block.
    Returns the frame's code block.  */
 
@@ -674,6 +709,9 @@ Return the reason why it's not possible to find frames older than this." },
   { "pc", frapy_pc, METH_NOARGS,
     "pc () -> Long.\n\
 Return the frame's resume address." },
+  { "read_register", frapy_read_register, METH_VARARGS,
+    "read_register (register_name) -> gdb.Value\n\
+Return the value of the register in the frame." },
   { "block", frapy_block, METH_NOARGS,
     "block () -> gdb.Block.\n\
 Return the frame's code block." },