Re: [PATCH] Pass noaliases_p to aarch64_decode_insn

[Yao Qi <qiyaoltc at gmail dot com>]

Hi Nick,

On 28/10/15 13:09, Nick Clifton wrote:
> This is a bit worrying, given that the interface is undocumented.  Plus 
> now we are changing it without updating any kind of version information. 
>   Not good, but not your fault either.
> 

Don't understand much your worry.  Both binutils and gdb are in the same
repository, and we always build them (opcodes and gdb) from source.  I
don't think we'll build gdb with opcodes library and headers in the future.

> 
>> This patch adds a new argument in aarch64_decode_insn, and pass 
>> no_aliases
>> to it.  In GDB side, always pass 1 to it.  Is it OK?
> 
>> -aarch64_decode_insn (aarch64_insn, aarch64_inst *);
>> +aarch64_decode_insn (aarch64_insn, aarch64_inst *, int);
> 
> I think that it would be better if the new parameter was a bfd_boolean 
> rather than an int.   The patch is approved with this change.

Thanks for the review.  Patch below is what I pushed in.

-- 
Yao (éå)
>From 43cdf5aeb8ae6ac2ec3bdbf636cbb2731ccbbb2a Mon Sep 17 00:00:00 2001
From: Yao Qi <yao.qi@linaro.org>
Subject: [PATCH] Pass noaliases_p to aarch64_decode_insn

Nowadays aarch64_decode_insn is a public interface used by both
opcodes and gdb.  However, its behaviour relies on a global variable
no_aliases, which isn't a good practise.  On the other hand, In default,
no_aliases is zero, but in GDB, we do want no alias when decoding
instructions for prologue analysis (patches to be posted), so that we
can handle both instructions "add" and "mov" (an alias of "add") as
"add".  The code in GDB can be simplified.

This patch adds a new argument in aarch64_decode_insn, and pass no_aliases
to it.  In GDB side, always pass 1 to it.

include/opcode:

2015-10-28  Yao Qi  <yao.qi@linaro.org>

	* aarch64.h (aarch64_decode_insn): Update declaration.

opcodes:

2015-10-28  Yao Qi  <yao.qi@linaro.org>

	* aarch64-dis.c	(aarch64_decode_insn): Add one argument
	noaliases_p.  Update comments.  Pass noaliases_p rather than
	no_aliases to aarch64_opcode_decode.
	(print_insn_aarch64_word): Pass no_aliases to
	aarch64_decode_insn.

gdb:

2015-10-28  Yao Qi  <yao.qi@linaro.org>

	* aarch64-tdep.c (aarch64_software_single_step): Pass 1 to
	aarch64_decode_insn.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0936194..181991a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-10-28  Yao Qi  <yao.qi@linaro.org>
+
+	* aarch64-tdep.c (aarch64_software_single_step): Pass 1 to
+	aarch64_decode_insn.
+
 2015-10-27  Pedro Alves  <palves@redhat.com>
 
 	* common/print-utils.c (host_address_to_string): Rename to ...
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 55c5fb8..d01a83f 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -2499,7 +2499,7 @@ aarch64_software_single_step (struct frame_info *frame)
   int last_breakpoint = 0; /* Defaults to 0 (no breakpoints placed).  */
   aarch64_inst inst;
 
-  if (aarch64_decode_insn (insn, &inst) != 0)
+  if (aarch64_decode_insn (insn, &inst, 1) != 0)
     return 0;
 
   /* Look for a Load Exclusive instruction which begins the sequence.  */
@@ -2512,7 +2512,7 @@ aarch64_software_single_step (struct frame_info *frame)
       insn = read_memory_unsigned_integer (loc, insn_size,
 					   byte_order_for_code);
 
-      if (aarch64_decode_insn (insn, &inst) != 0)
+      if (aarch64_decode_insn (insn, &inst, 1) != 0)
 	return 0;
       /* Check if the instruction is a conditional branch.  */
       if (inst.opcode->iclass == condbranch)
diff --git a/include/opcode/ChangeLog b/include/opcode/ChangeLog
index ea833f7..b049302 100644
--- a/include/opcode/ChangeLog
+++ b/include/opcode/ChangeLog
@@ -1,3 +1,7 @@
+2015-10-28  Yao Qi  <yao.qi@linaro.org>
+
+	* aarch64.h (aarch64_decode_insn): Update declaration.
+
 2015-10-07  Yao Qi  <yao.qi@linaro.org>
 
 	* aarch64.h (aarch64_sys_ins_reg) <template>: Removed.
diff --git a/include/opcode/aarch64.h b/include/opcode/aarch64.h
index c423858..711f7e5 100644
--- a/include/opcode/aarch64.h
+++ b/include/opcode/aarch64.h
@@ -930,7 +930,7 @@ extern int
 aarch64_zero_register_p (const aarch64_opnd_info *);
 
 extern int
-aarch64_decode_insn (aarch64_insn, aarch64_inst *);
+aarch64_decode_insn (aarch64_insn, aarch64_inst *, bfd_boolean);
 
 /* Given an operand qualifier, return the expected data element size
    of a qualified operand.  */
diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index d0f7771..8952872 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,11 @@
+2015-10-28  Yao Qi  <yao.qi@linaro.org>
+
+	* aarch64-dis.c	(aarch64_decode_insn): Add one argument
+	noaliases_p.  Update comments.  Pass noaliases_p rather than
+	no_aliases to aarch64_opcode_decode.
+	(print_insn_aarch64_word): Pass no_aliases to
+	aarch64_decode_insn.
+
 2015-10-27  Vinay  <Vinay.G@kpit.com>
 
 	PR binutils/19159
diff --git a/opcodes/aarch64-dis.c b/opcodes/aarch64-dis.c
index 9b96cff..93766c6 100644
--- a/opcodes/aarch64-dis.c
+++ b/opcodes/aarch64-dis.c
@@ -2029,11 +2029,13 @@ user_friendly_fixup (aarch64_inst *inst)
     }
 }
 
-/* Decode INSN and fill in *INST the instruction information.  Return zero
-   on success.  */
+/* Decode INSN and fill in *INST the instruction information.  An alias
+   opcode may be filled in *INSN if NOALIASES_P is FALSE.  Return zero on
+   success.  */
 
 int
-aarch64_decode_insn (aarch64_insn insn, aarch64_inst *inst)
+aarch64_decode_insn (aarch64_insn insn, aarch64_inst *inst,
+		     bfd_boolean noaliases_p)
 {
   const aarch64_opcode *opcode = aarch64_opcode_lookup (insn);
 
@@ -2060,7 +2062,7 @@ aarch64_decode_insn (aarch64_insn insn, aarch64_inst *inst)
     {
       /* But only one opcode can be decoded successfully for, as the
 	 decoding routine will check the constraint carefully.  */
-      if (aarch64_opcode_decode (opcode, insn, inst, no_aliases) == 1)
+      if (aarch64_opcode_decode (opcode, insn, inst, noaliases_p) == 1)
 	return ERR_OK;
       opcode = aarch64_find_next_opcode (opcode);
     }
@@ -2172,7 +2174,7 @@ print_insn_aarch64_word (bfd_vma pc,
        addresses, since the addend is not currently pc-relative.  */
     pc = 0;
 
-  ret = aarch64_decode_insn (word, &inst);
+  ret = aarch64_decode_insn (word, &inst, no_aliases);
 
   if (((word >> 21) & 0x3ff) == 1)
     {