[PATCH 3/9] gdb/disasm: read opcodes bytes with a single read_code call

[Andrew Burgess <aburgess@redhat.com>]

This commit reduces the number of times we call read_code when
printing the instruction opcode bytes during disassembly.

I've added a new gdb::byte_vector within the
gdb_pretty_print_disassembler class, in line with all the other
buffers that gdb_pretty_print_disassembler needs.  This byte_vector is
then resized as needed, and filled with a single read_code call for
each instruction.

There should be no user visible changes after this commit.
---
 gdb/disasm.c | 16 +++++++---------
 gdb/disasm.h |  3 +++
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/gdb/disasm.c b/gdb/disasm.c
index c6edc92930d..42351c735d3 100644
--- a/gdb/disasm.c
+++ b/gdb/disasm.c
@@ -323,21 +323,19 @@ gdb_pretty_print_disassembler::pretty_print_insn (const struct disasm_insn *insn
 
     if (flags & DISASSEMBLY_RAW_INSN)
       {
-	CORE_ADDR end_pc;
-	bfd_byte data;
-	const char *spacer = "";
-
 	/* Build the opcodes using a temporary stream so we can
 	   write them out in a single go for the MI.  */
 	m_opcode_stb.clear ();
 
-	end_pc = pc + size;
+	/* Read the instruction opcode data.  */
+	m_opcode_data.resize (size);
+	read_code (pc, m_opcode_data.data (), size);
 
-	for (;pc < end_pc; ++pc)
+	for (int i = 0; i < size; ++i)
 	  {
-	    read_code (pc, &data, 1);
-	    m_opcode_stb.printf ("%s%02x", spacer, (unsigned) data);
-	    spacer = " ";
+	    if (i > 0)
+	      m_opcode_stb.puts (" ");
+	    m_opcode_stb.printf ("%02x", (unsigned) m_opcode_data[i]);
 	  }
 
 	m_uiout->field_stream ("opcodes", m_opcode_stb);
diff --git a/gdb/disasm.h b/gdb/disasm.h
index da03e130526..13403042709 100644
--- a/gdb/disasm.h
+++ b/gdb/disasm.h
@@ -311,6 +311,9 @@ class gdb_pretty_print_disassembler
 
   /* The buffer used to build the raw opcodes string.  */
   string_file m_opcode_stb;
+
+  /* The buffer used to hold the opcode bytes (if required).  */
+  gdb::byte_vector m_opcode_data;
 };
 
 /* Return the length in bytes of the instruction at address MEMADDR in
-- 
2.25.4