trace: add some tcg tracing support

This adds a couple of tcg specific trace-events which are useful for
tracing execution though tcg generated blocks. It's been tested with
lttng user space tracing but is generic enough for all systems. The tcg
events are:

  * translate_block - when a subject block is translated
  * exec_tb - when a translated block is entered
  * exec_tb_exit - when we exit the translated code
  * exec_tb_nocache - special case translations

Of course we can only trace the entrance to the first block of a chain
as each block will jump directly to the next when it can. See the -d
nochain patch to allow more complete tracing at the expense of
performance.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

translate-all.c

@@ -33,6 +33,7 @@
 #include "qemu-common.h"
 #define NO_CPU_IO_DEFS
 #include "cpu.h"
+#include "trace.h"
 #include "disas/disas.h"
 #include "tcg.h"
 #if defined(CONFIG_USER_ONLY)
@@ -158,6 +159,8 @@ int cpu_gen_code(CPUArchState *env, TranslationBlock *tb, int *gen_code_size_ptr
 
     gen_intermediate_code(env, tb);
 
+    trace_translate_block(tb, tb->pc, tb->tc_ptr);
+
     /* generate machine code */
     gen_code_buf = tb->tc_ptr;
     tb->tb_next_offset[0] = 0xffff;