disasm: add struct disasm_insn to describe to-be-disassembled instruction

The "record instruction-history" command prints for each instruction in
addition to the instruction's disassembly:

  - the instruction number in the recorded execution trace
  - a '?' before the instruction if it was executed speculatively

To allow the "record instruction-history" command to use GDB's disassembly
infrastructure, we extend gdb_pretty_print_insn to optionally print those
additional fields and export the function.

Add a new struct disasm_insn to add additional fields describing the
to-be-disassembled instruction.  The additional fields are:

  number            an optional instruction number, zero if omitted.
  is_speculative    a predicate saying whether the instruction was
                    executed speculatively.

If non-zero, the instruction number is printed first.  It will also appear
as a new optional field "insn-number" in MI.  The field will be present if
insn_num is non-zero.

If is_speculative is set, speculative execution will be indicated by a "?"
following the new instruction number field.  Unless the PC is omitted, it
will overwrite the first byte of the PC prefix.  It will appear as a new
optional field "is-speculative" in MI.  The field will contain "?" and will
be present if is_speculative is set.

The speculative execution indication is guarded by a new flag
DISASSEMBLY_SPECULATION.

Replace the PC parameter of gdb_pretty_print_insn with a pointer to the above
struct.  GDB's "disassemble" command does not use the new fields.

gdb/
	* disasm.h (DISASSEMBLY_SPECULATION): New.
	(struct disasm_insn): New.
	(gdb_pretty_print_insn): New.
	* disasm.c (gdb_pretty_print_insn): Replace parameter PC with INSN.
	Update users.  Print instruction number and indicate speculative
	execution, if requested.

gdb/ChangeLog

@@ -1,3 +1,12 @@
+2015-11-04  Markus Metzger  <markus.t.metzger@intel.com>
+
+	* disasm.h (DISASSEMBLY_SPECULATION): New.
+	(struct disasm_insn): New.
+	(gdb_pretty_print_insn): New.
+	* disasm.c (gdb_pretty_print_insn): Replace parameter PC with INSN.
+	Update users.  Print instruction number and indicate speculative
+	execution, if requested.
+
 2015-11-04  Markus Metzger  <markus.t.metzger@intel.com>
 
 	* disasm.c (dump_insns): Split into this and ...

gdb/disasm.c

@@ -170,12 +170,12 @@ compare_lines (const void *mle1p, const void *mle2p)
   return val;
 }
 
-/* Prints the instruction at PC into UIOUT and returns the length of the
+/* See disasm.h.  */
-   printed instruction in bytes.  */
 
-static int
+int
 gdb_pretty_print_insn (struct gdbarch *gdbarch, struct ui_out *uiout,
-		       struct disassemble_info * di, CORE_ADDR pc, int flags,
+		       struct disassemble_info * di,
+		       const struct disasm_insn *insn, int flags,
 		       struct ui_file *stb)
 {
   /* parts of the symbolic representation of the address */
@@ -186,10 +186,37 @@ gdb_pretty_print_insn (struct gdbarch *gdbarch, struct ui_out *uiout,
   struct cleanup *ui_out_chain;
   char *filename = NULL;
   char *name = NULL;
+  CORE_ADDR pc;
 
   ui_out_chain = make_cleanup_ui_out_tuple_begin_end (uiout, NULL);
+  pc = insn->addr;
 
+  if (insn->number != 0)
+    {
+      ui_out_field_fmt (uiout, "insn-number", "%u", insn->number);
+      ui_out_text (uiout, "\t");
+    }
+
+  if ((flags & DISASSEMBLY_SPECULATIVE) != 0)
+    {
+      if (insn->is_speculative)
+	{
+	  ui_out_field_string (uiout, "is-speculative", "?");
+
+	  /* The speculative execution indication overwrites the first
+	     character of the PC prefix.
+	     We assume a PC prefix length of 3 characters.  */
 	  if ((flags & DISASSEMBLY_OMIT_PC) == 0)
+	    ui_out_text (uiout, pc_prefix (pc) + 1);
+	  else
+	    ui_out_text (uiout, "  ");
+	}
+      else if ((flags & DISASSEMBLY_OMIT_PC) == 0)
+	ui_out_text (uiout, pc_prefix (pc));
+      else
+	ui_out_text (uiout, "   ");
+    }
+  else if ((flags & DISASSEMBLY_OMIT_PC) == 0)
     ui_out_text (uiout, pc_prefix (pc));
   ui_out_field_core_addr (uiout, "address", gdbarch, pc);
 
@@ -263,25 +290,29 @@ dump_insns (struct gdbarch *gdbarch, struct ui_out *uiout,
 	    int how_many, int flags, struct ui_file *stb,
 	    CORE_ADDR *end_pc)
 {
+  struct disasm_insn insn;
   int num_displayed = 0;
 
-  while (low < high && (how_many < 0 || num_displayed < how_many))
+  memset (&insn, 0, sizeof (insn));
+  insn.addr = low;
+
+  while (insn.addr < high && (how_many < 0 || num_displayed < how_many))
     {
       int size;
 
-      size = gdb_pretty_print_insn (gdbarch, uiout, di, low, flags, stb);
+      size = gdb_pretty_print_insn (gdbarch, uiout, di, &insn, flags, stb);
       if (size <= 0)
 	break;
 
       ++num_displayed;
-      low += size;
+      insn.addr += size;
 
       /* Allow user to bail out with ^C.  */
       QUIT;
     }
 
   if (end_pc != NULL)
-    *end_pc = low;
+    *end_pc = insn.addr;
 
   return num_displayed;
 }

gdb/disasm.h

@@ -27,11 +27,34 @@
 #define DISASSEMBLY_FILENAME	(0x1 << 3)
 #define DISASSEMBLY_OMIT_PC	(0x1 << 4)
 #define DISASSEMBLY_SOURCE	(0x1 << 5)
+#define DISASSEMBLY_SPECULATIVE	(0x1 << 6)
 
 struct gdbarch;
 struct ui_out;
 struct ui_file;
 
+/* An instruction to be disassembled.  */
+
+struct disasm_insn
+{
+  /* The address of the memory containing the instruction.  */
+  CORE_ADDR addr;
+
+  /* An optional instruction number.  If non-zero, it is printed first.  */
+  unsigned int number;
+
+  /* True if the instruction was executed speculatively.  */
+  unsigned int is_speculative:1;
+};
+
+/* Prints the instruction INSN into UIOUT and returns the length of the
+   printed instruction in bytes.  */
+
+extern int gdb_pretty_print_insn (struct gdbarch *gdbarch, struct ui_out *uiout,
+				  struct disassemble_info * di,
+				  const struct disasm_insn *insn, int flags,
+				  struct ui_file *stb);
+
 /* Return a filled in disassemble_info object for use by gdb.  */
 
 extern struct disassemble_info gdb_disassemble_info (struct gdbarch *gdbarch,