From: Pierre Langlois <pierre.langlois@embecosm.com>
Date: Fri, 25 Jul 2014 13:45:03 +0000 (+0100)
Subject: Clarify the address and pointer conversions on AVR.
X-Git-Tag: binutils-2_25~737
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=7d0d9d2bee341b1e88c559c476f15fc24b6de346;p=external%2Fbinutils.git

Clarify the address and pointer conversions on AVR.

This patch adds additional comments about the conversion of addresses to
pointers and vice-versa on AVR.

Special conversion needs to be done when dealing with an address in the
flash address space, where both code and read-only data can be stored.
Code and data pointers to flash are not addressed the same way:

A code pointer is 16 bit addressed.  A data pointer is 8 bit addressed,
even if the data is in flash.

2014-07-25  Pierre Langlois  <pierre.langlois@embecosm.com>

	* avr-tdep.c (avr_address_to_pointer): Clarify the conversion in the
	comments.
	(avr_pointer_to_address): Likewise.
---

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b0c79b5..f265915 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2014-07-25  Pierre Langlois  <pierre.langlois@embecosm.com>
+
+	* avr-tdep.c (avr_address_to_pointer): Clarify the conversion in the
+	comments.
+	(avr_pointer_to_address): Likewise.
+
 2014-07-24  Tom Tromey  <tromey@redhat.com>
 
 	* monitor.c (compile_pattern): Update.
diff --git a/gdb/avr-tdep.c b/gdb/avr-tdep.c
index be0b543..1f268f2 100644
--- a/gdb/avr-tdep.c
+++ b/gdb/avr-tdep.c
@@ -308,7 +308,7 @@ avr_address_to_pointer (struct gdbarch *gdbarch,
   /* Is it a data address in flash?  */
   if (AVR_TYPE_ADDRESS_CLASS_FLASH (type))
     {
-      /* A data address in flash is always byte addressed.  */
+      /* A data pointer in flash is byte addressed.  */
       store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order,
 			      avr_convert_iaddr_to_raw (addr));
     }
@@ -316,8 +316,8 @@ avr_address_to_pointer (struct gdbarch *gdbarch,
   else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
 	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
     {
-      /* A code address, either a function pointer or the program counter, is
-	 word (16 bits) addressed.  */
+      /* A code pointer is word (16 bits) addressed.  We shift the address down
+	 by 1 bit to convert it to a pointer.  */
       store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order,
 			      avr_convert_iaddr_to_raw (addr >> 1));
     }
@@ -339,12 +339,19 @@ avr_pointer_to_address (struct gdbarch *gdbarch,
 
   /* Is it a data address in flash?  */
   if (AVR_TYPE_ADDRESS_CLASS_FLASH (type))
-    return avr_make_iaddr (addr);
+    {
+      /* A data pointer in flash is already byte addressed.  */
+      return avr_make_iaddr (addr);
+    }
   /* Is it a code address?  */
   else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
 	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
 	   || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
-    return avr_make_iaddr (addr << 1);
+    {
+      /* A code pointer is word (16 bits) addressed so we shift it up
+	 by 1 bit to convert it to an address.  */
+      return avr_make_iaddr (addr << 1);
+    }
   else
     return avr_make_saddr (addr);
 }