bfd/ChangeLog

	* elf32-avr.c: Add DIFF relocations for AVR.
	(avr_final_link_relocate): Handle the DIFF relocs.
	(bfd_elf_avr_diff_reloc): New.
	(elf32_avr_is_diff_reloc): New.
	(elf32_avr_adjust_diff_reloc_value): Reduce difference value.
	(elf32_avr_relax_delete_bytes): Recompute difference after deleting
	bytes.

	* reloc.c: Add BFD_RELOC_AVR_DIFF8/16/32 relocations

gas/ChangeLog

	* config/tc-avr.c: Add new flag mlink-relax.
	(md_show_usage): Add flag and help text.
	(md_parse_option): Record whether link relax is turned on.
	(relaxable_section): New.
	(avr_validate_fix_sub): New.
	(avr_force_relocation): New.
	(md_apply_fix): Generate DIFF reloc.
	(avr_allow_local_subtract): New.

	* config/tc-avr.h (TC_LINKRELAX_FIXUP): Define to 0.
	(TC_FORCE_RELOCATION): Define.
	(TC_FORCE_RELOCATION_SUB_SAME): Define.
	(TC_VALIDATE_FIX_SUB): Define.
	(avr_force_relocation): Declare.
	(avr_validate_fix_sub): Declare.
	(md_allow_local_subtract): Define.
	(avr_allow_local_subtract): Declare.

gas/testsuite/ChangeLog

	* gas/avr/diffreloc_withrelax.d: New testcase.
	* gas/avr/noreloc_withoutrelax.d: Likewise.
	* gas/avr/relax.s: Likewise.

include/ChangeLog

	* elf/avr.h: Add new DIFF relocs.

ld/testsuite/ChangeLog

	* ld-avr/norelax_diff.d: New testcase.
	* ld-avr/relax_diff.d: Likewise.
	* ld-avr/relax.s: Likewise.

3 files changed, 206 insertions, 2 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index e38c6a4..0fc016c 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,15 @@
+2014-04-10  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	* elf32-avr.c: Add DIFF relocations for AVR.
+	(avr_final_link_relocate): Handle the DIFF relocs.
+	(bfd_elf_avr_diff_reloc): New.
+	(elf32_avr_is_diff_reloc): New.
+	(elf32_avr_adjust_diff_reloc_value): Reduce difference value.
+	(elf32_avr_relax_delete_bytes): Recompute difference after deleting
+	bytes.
+
+	* reloc.c: Add BFD_RELOC_AVR_DIFF8/16/32 relocations
+
 2014-04-09  Alan Modra  <amodra@gmail.com>
 
 	* libcoff.h: Regenerate.
diff --git a/bfd/elf32-avr.c b/bfd/elf32-avr.c
index 3fd43c9..425e2d1 100644
--- a/bfd/elf32-avr.c
+++ b/bfd/elf32-avr.c
@@ -32,6 +32,15 @@ static bfd_boolean debug_relax = FALSE;
 /* Enable debugging printout at stdout with this variable.  */
 static bfd_boolean debug_stubs = FALSE;
 
+static bfd_reloc_status_type
+bfd_elf_avr_diff_reloc (bfd *abfd,
+              arelent *reloc_entry,
+              asymbol *symbol,
+              void *data,
+              asection *input_section,
+              bfd *output_bfd,
+              char **error_message);
+
 /* Hash table initialization and handling.  Code is taken from the hppa port
    and adapted to the needs of AVR.  */
 
@@ -557,6 +566,45 @@ static reloc_howto_type elf_avr_howto_table[] =
 	 0xffffff,		/* src_mask */
 	 0xffffff,		/* dst_mask */
 	 FALSE),		/* pcrel_offset */
+  HOWTO (R_AVR_DIFF8,      /* type */
+     0,             /* rightshift */
+     0, 			/* size (0 = byte, 1 = short, 2 = long) */
+     8, 			/* bitsize */
+     FALSE,         /* pc_relative */
+     0,             /* bitpos */
+     complain_overflow_bitfield, /* complain_on_overflow */
+     bfd_elf_avr_diff_reloc, /* special_function */
+     "R_AVR_DIFF8",     /* name */
+     FALSE,         /* partial_inplace */
+     0,             /* src_mask */
+     0xff,          /* dst_mask */
+     FALSE),        /* pcrel_offset */
+  HOWTO (R_AVR_DIFF16,     /* type */
+     0,             /* rightshift */
+     1,			/* size (0 = byte, 1 = short, 2 = long) */
+     16,			/* bitsize */
+     FALSE,         /* pc_relative */
+     0,             /* bitpos */
+     complain_overflow_bitfield, /* complain_on_overflow */
+     bfd_elf_avr_diff_reloc, /* special_function */
+     "R_AVR_DIFF16",     /* name */
+     FALSE,         /* partial_inplace */
+     0,             /* src_mask */
+     0xffff,        /* dst_mask */
+     FALSE),        /* pcrel_offset */
+  HOWTO (R_AVR_DIFF32,    /* type */
+     0,             /* rightshift */
+     2,         /* size (0 = byte, 1 = short, 2 = long) */
+     32,        /* bitsize */
+     FALSE,         /* pc_relative */
+     0,             /* bitpos */
+     complain_overflow_bitfield, /* complain_on_overflow */
+     bfd_elf_avr_diff_reloc, /* special_function */
+     "R_AVR_DIFF32",     /* name */
+     FALSE,         /* partial_inplace */
+     0,             /* src_mask */
+     0xffffffff,    /* dst_mask */ 
+     FALSE)         /* pcrel_offset */
 };
 
 /* Map BFD reloc types to AVR ELF reloc types.  */
@@ -598,7 +646,10 @@ static const struct avr_reloc_map avr_reloc_map[] =
   { BFD_RELOC_8,                    R_AVR_8 },
   { BFD_RELOC_AVR_8_LO,             R_AVR_8_LO8 },
   { BFD_RELOC_AVR_8_HI,             R_AVR_8_HI8 },
-  { BFD_RELOC_AVR_8_HLO,            R_AVR_8_HLO8 }
+  { BFD_RELOC_AVR_8_HLO,            R_AVR_8_HLO8 },
+  { BFD_RELOC_AVR_DIFF8,            R_AVR_DIFF8 },
+  { BFD_RELOC_AVR_DIFF16,           R_AVR_DIFF16 },
+  { BFD_RELOC_AVR_DIFF32,           R_AVR_DIFF32 }
 };
 
 /* Meant to be filled one day with the wrap around address for the
@@ -797,6 +848,22 @@ avr_get_stub_addr (bfd_vma srel,
   return 0x020000;
 }
 
+/* Perform a diff relocation. Nothing to do, as the difference value is already
+   written into the section's contents. */
+
+static bfd_reloc_status_type
+bfd_elf_avr_diff_reloc (bfd *abfd ATTRIBUTE_UNUSED,
+		      arelent *reloc_entry ATTRIBUTE_UNUSED,
+              asymbol *symbol ATTRIBUTE_UNUSED,
+              void *data ATTRIBUTE_UNUSED,
+              asection *input_section ATTRIBUTE_UNUSED,
+              bfd *output_bfd ATTRIBUTE_UNUSED,
+              char **error_message ATTRIBUTE_UNUSED)
+{
+  return bfd_reloc_ok;
+}
+
+
 /* Perform a single relocation.  By default we use the standard BFD
    routines, but a few relocs, we have to do them ourselves.  */
 
@@ -1149,6 +1216,13 @@ avr_final_link_relocate (reloc_howto_type *                 howto,
       bfd_put_16 (input_bfd, (bfd_vma) srel &0x00ffff, contents);
       break;
 
+    case R_AVR_DIFF8:
+    case R_AVR_DIFF16:
+    case R_AVR_DIFF32:
+      /* Nothing to do here, as contents already contains the diff value. */
+      r = bfd_reloc_ok;
+      break;
+
     default:
       r = _bfd_final_link_relocate (howto, input_bfd, input_section,
 				    contents, rel->r_offset,
@@ -1457,6 +1531,104 @@ elf32_avr_object_p (bfd *abfd)
 				    e_set);
 }
 
+/* Returns whether the relocation type passed is a diff reloc. */
+
+static bfd_boolean
+elf32_avr_is_diff_reloc (Elf_Internal_Rela *irel)
+{
+  return (ELF32_R_TYPE (irel->r_info) == R_AVR_DIFF8
+          ||ELF32_R_TYPE (irel->r_info) == R_AVR_DIFF16
+          || ELF32_R_TYPE (irel->r_info) == R_AVR_DIFF32);
+}
+
+/* Reduce the diff value written in the section by count if the shrinked 
+   insn address happens to fall between the two symbols for which this 
+   diff reloc was emitted. */
+
+static void
+elf32_avr_adjust_diff_reloc_value (bfd *abfd,
+                                   struct bfd_section *isec,
+                                   Elf_Internal_Rela *irel,
+                                   bfd_vma symval,
+                                   bfd_vma shrinked_insn_address,
+                                   int count)
+{
+  unsigned char *reloc_contents = NULL;
+  unsigned char *isec_contents = elf_section_data (isec)->this_hdr.contents;
+  if (isec_contents == NULL)
+  {
+    if (! bfd_malloc_and_get_section (abfd, isec, &isec_contents))
+      return;
+
+    elf_section_data (isec)->this_hdr.contents = isec_contents;
+  }
+
+  reloc_contents = isec_contents + irel->r_offset;
+
+  /* Read value written in object file. */
+ bfd_vma x = 0;
+  switch (ELF32_R_TYPE (irel->r_info))
+  {
+  case R_AVR_DIFF8:
+    {
+      x = *reloc_contents;
+      break;
+    }
+  case R_AVR_DIFF16:
+    {
+      x = bfd_get_16 (abfd, reloc_contents);
+      break;
+    }
+  case R_AVR_DIFF32:
+    {
+      x = bfd_get_32 (abfd, reloc_contents);
+      break;
+    }
+  default:
+    {
+      BFD_FAIL();
+    }
+  }
+
+  /* For a diff reloc sym1 - sym2 the diff at assembly time (x) is written
+     into the object file at the reloc offset. sym2's logical value is
+     symval (<start_of_section>) + reloc addend. Compute the start and end
+     addresses and check if the shrinked insn falls between sym1 and sym2. */
+
+  bfd_vma end_address = symval + irel->r_addend;
+  bfd_vma start_address = end_address - x;
+
+  /* Reduce the diff value by count bytes and write it back into section 
+    contents. */
+
+  if (shrinked_insn_address >= start_address && 
+      shrinked_insn_address <= end_address)
+  {
+    switch (ELF32_R_TYPE (irel->r_info))
+    {
+    case R_AVR_DIFF8:
+      {
+        *reloc_contents = (x - count);
+        break;
+      }
+    case R_AVR_DIFF16:
+      {
+        bfd_put_16 (abfd, (x - count) & 0xFFFF, reloc_contents);
+        break;
+      }
+    case R_AVR_DIFF32:
+      {
+        bfd_put_32 (abfd, (x - count) & 0xFFFFFFFF, reloc_contents);
+        break;
+      }
+    default:
+      {
+        BFD_FAIL();
+      }
+    }
+
+  }
+}
 
 /* Delete some bytes from a section while changing the size of an instruction.
    The parameter "addr" denotes the section-relative offset pointing just
@@ -1595,6 +1767,14 @@ elf32_avr_relax_delete_bytes (bfd *abfd,
                    if (symval <= shrinked_insn_address
                        && (symval + irel->r_addend) > shrinked_insn_address)
                      {
+                       if (elf32_avr_is_diff_reloc (irel))
+                         {
+                           elf32_avr_adjust_diff_reloc_value (abfd, isec, irel,
+                                                         symval,
+                                                         shrinked_insn_address,
+                                                        count);
+                         }
+
                        irel->r_addend -= count;
 
                        if (debug_relax)
diff --git a/bfd/reloc.c b/bfd/reloc.c
index 5a7d0e9..7ca3cfd 100644
--- a/bfd/reloc.c
+++ b/bfd/reloc.c
@@ -4780,7 +4780,19 @@ ENUM
 ENUMDOC
   This is a 8 bit reloc for the AVR that stores bits 16..23 of a symbol
   in .byte hlo8(symbol)
-
+ENUM
+  BFD_RELOC_AVR_DIFF8
+ENUMX
+  BFD_RELOC_AVR_DIFF16
+ENUMX
+  BFD_RELOC_AVR_DIFF32
+ENUMDOC
+  AVR relocations to mark the difference of two local symbols.
+  These are only needed to support linker relaxation and can be ignored
+  when not relaxing.  The field is set to the value of the difference
+  assuming no relaxation.  The relocation encodes the position of the
+  second symbol so the linker can determine whether to adjust the field
+  value.
 ENUM
   BFD_RELOC_RL78_NEG8
 ENUMX