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.

7 files changed, 215 insertions, 3 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 326b47c..d7e5b4a 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,23 @@
+2014-04-10  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	* 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.
+
 2014-04-10  Andrew Bennett  <andrew.bennett@imgtec.com>
 
 	* config/tc-mips.c (mips_cpu_info_table): Add P5600
diff --git a/gas/config/tc-avr.c b/gas/config/tc-avr.c
index ce9708e..e4bc59c 100644
--- a/gas/config/tc-avr.c
+++ b/gas/config/tc-avr.c
@@ -338,9 +338,11 @@ struct avr_opt_s
   int all_opcodes;  /* -mall-opcodes: accept all known AVR opcodes.  */
   int no_skip_bug;  /* -mno-skip-bug: no warnings for skipping 2-word insns.  */
   int no_wrap;      /* -mno-wrap: reject rjmp/rcall with 8K wrap-around.  */
+  int link_relax;   /* -mlink-relax: generate relocations for linker 
+                       relaxation. */
 };
 
-static struct avr_opt_s avr_opt = { 0, 0, 0 };
+static struct avr_opt_s avr_opt = { 0, 0, 0, 0 };
 
 const char EXP_CHARS[] = "eE";
 const char FLT_CHARS[] = "dD";
@@ -401,7 +403,8 @@ enum options
   OPTION_ALL_OPCODES = OPTION_MD_BASE + 1,
   OPTION_NO_SKIP_BUG,
   OPTION_NO_WRAP,
-  OPTION_ISA_RMW
+  OPTION_ISA_RMW,
+  OPTION_LINK_RELAX
 };
 
 struct option md_longopts[] =
@@ -411,6 +414,7 @@ struct option md_longopts[] =
   { "mno-skip-bug", no_argument, NULL, OPTION_NO_SKIP_BUG },
   { "mno-wrap",     no_argument, NULL, OPTION_NO_WRAP     },
   { "mrmw",         no_argument, NULL, OPTION_ISA_RMW     },
+  { "mlink-relax",  no_argument, NULL, OPTION_LINK_RELAX  },
   { NULL, no_argument, NULL, 0 }
 };
 
@@ -517,6 +521,7 @@ md_show_usage (FILE *stream)
 	"  -mno-wrap        reject rjmp/rcall instructions with 8K wrap-around\n"
 	"                   (default for avr3, avr5)\n"
 	"  -mrmw            accept Read-Modify-Write instructions\n"
+    "  -mlink-relax     generate relocations for linker relaxation\n"
     ));
   show_mcu_list (stream);
 }
@@ -587,6 +592,9 @@ md_parse_option (int c, char *arg)
     case OPTION_ISA_RMW:
       specified_mcu.isa |= AVR_ISA_RMW;
       return 1;
+    case OPTION_LINK_RELAX:
+      avr_opt.link_relax = 1;
+      return 1;
     }
 
   return 0;
@@ -637,6 +645,7 @@ md_begin (void)
     }
 
   bfd_set_arch_mach (stdoutput, TARGET_ARCH, avr_mcu->mach);
+  linkrelax = avr_opt.link_relax;
 }
 
 /* Resolve STR as a constant expression and return the result.
@@ -1200,6 +1209,53 @@ md_pcrel_from_section (fixS *fixp, segT sec)
   return fixp->fx_frag->fr_address + fixp->fx_where;
 }
 
+static bfd_boolean
+relaxable_section (asection *sec)
+{
+  return (sec->flags & SEC_DEBUGGING) == 0;
+}
+
+/* Does whatever the xtensa port does. */
+int
+avr_validate_fix_sub (fixS *fix)
+{
+  segT add_symbol_segment, sub_symbol_segment;
+
+  /* The difference of two symbols should be resolved by the assembler when
+     linkrelax is not set.  If the linker may relax the section containing
+     the symbols, then an Xtensa DIFF relocation must be generated so that
+     the linker knows to adjust the difference value.  */
+  if (!linkrelax || fix->fx_addsy == NULL)
+    return 0;
+
+  /* Make sure both symbols are in the same segment, and that segment is
+     "normal" and relaxable.  If the segment is not "normal", then the
+     fix is not valid.  If the segment is not "relaxable", then the fix
+     should have been handled earlier.  */
+  add_symbol_segment = S_GET_SEGMENT (fix->fx_addsy);
+  if (! SEG_NORMAL (add_symbol_segment) ||
+      ! relaxable_section (add_symbol_segment))
+    return 0;
+
+  sub_symbol_segment = S_GET_SEGMENT (fix->fx_subsy);
+  return (sub_symbol_segment == add_symbol_segment);
+}
+
+/* TC_FORCE_RELOCATION hook */
+
+/* If linkrelax is turned on, and the symbol to relocate
+   against is in a relaxable segment, don't compute the value -
+   generate a relocation instead. */
+int
+avr_force_relocation (fixS *fix)
+{
+  if (linkrelax && fix->fx_addsy
+      && relaxable_section (S_GET_SEGMENT (fix->fx_addsy)))
+    return 1;
+
+  return generic_force_reloc (fix);
+}
+
 /* GAS will call this for each fixup.  It should store the correct
    value in the object file.  */
 
@@ -1223,11 +1279,47 @@ md_apply_fix (fixS *fixP, valueT * valP, segT seg)
 	  fixP->fx_done = 1;
 	}
     }
-
+  else if (linkrelax && fixP->fx_subsy)
+    {
+      /* For a subtraction relocation expression, generate one
+         of the DIFF relocs, with the value being the difference.
+         Note that a sym1 - sym2 expression is adjusted into a
+         section_start_sym + sym4_offset_from_section_start - sym1
+         expression. fixP->fx_addsy holds the section start symbol,
+         fixP->fx_offset holds sym2's offset, and fixP->fx_subsy
+         holds sym1. Calculate the current difference and write value,
+         but leave fx_offset as is - during relaxation, 
+         fx_offset - value gives sym1's value */
+
+       switch (fixP->fx_r_type)
+         {
+           case BFD_RELOC_8:
+             fixP->fx_r_type = BFD_RELOC_AVR_DIFF8;
+             break;
+           case BFD_RELOC_16:
+             fixP->fx_r_type = BFD_RELOC_AVR_DIFF16;
+             break;
+           case BFD_RELOC_32:
+             fixP->fx_r_type = BFD_RELOC_AVR_DIFF32;
+             break;
+           default:
+             as_bad_where (fixP->fx_file, fixP->fx_line, _("expression too complex"));
+             break;
+         }
+
+      value = S_GET_VALUE (fixP->fx_addsy) +
+          fixP->fx_offset - S_GET_VALUE (fixP->fx_subsy);
+
+      fixP->fx_subsy = NULL;
+  }
   /* We don't actually support subtracting a symbol.  */
   if (fixP->fx_subsy != (symbolS *) NULL)
     as_bad_where (fixP->fx_file, fixP->fx_line, _("expression too complex"));
 
+  /* For the DIFF relocs, write the value into the object file while still
+     keeping fx_done FALSE, as both the difference (recorded in the object file)
+     and the sym offset (part of fixP) are needed at link relax time */
+  where = (unsigned char *) fixP->fx_frag->fr_literal + fixP->fx_where;
   switch (fixP->fx_r_type)
     {
     default:
@@ -1237,6 +1329,16 @@ md_apply_fix (fixS *fixP, valueT * valP, segT seg)
     case BFD_RELOC_AVR_13_PCREL:
     case BFD_RELOC_32:
     case BFD_RELOC_16:
+      break;
+    case BFD_RELOC_AVR_DIFF8:
+      *where = value;
+	  break;
+    case BFD_RELOC_AVR_DIFF16:
+      bfd_putl16 ((bfd_vma) value, where);
+      break;
+    case BFD_RELOC_AVR_DIFF32:
+      bfd_putl32 ((bfd_vma) value, where);
+      break;
     case BFD_RELOC_AVR_CALL:
       break;
     }
@@ -1654,3 +1756,25 @@ tc_cfi_frame_initial_instructions (void)
      do not line up the same way as for targers that use pre-decrement.  */
   cfi_add_CFA_offset (DWARF2_DEFAULT_RETURN_COLUMN, 1-return_size);
 }
+
+bfd_boolean
+avr_allow_local_subtract (expressionS * left,
+			     expressionS * right,
+			     segT section)
+{
+  /* If we are not in relaxation mode, subtraction is OK. */
+  if (!linkrelax)
+    return TRUE;
+
+  /* If the symbols are not in a code section then they are OK.  */
+  if ((section->flags & SEC_CODE) == 0)
+    return TRUE;
+
+  if (left->X_add_symbol == right->X_add_symbol)
+    return TRUE;
+
+  /* We have to assume that there may be instructions between the
+     two symbols and that relaxation may increase the distance between
+     them.  */
+  return FALSE;
+}
diff --git a/gas/config/tc-avr.h b/gas/config/tc-avr.h
index df75ac7..fb596ad 100644
--- a/gas/config/tc-avr.h
+++ b/gas/config/tc-avr.h
@@ -112,6 +112,18 @@ extern void avr_cons_fix_new (fragS *,int, int, expressionS *,
    visible symbols can be overridden.  */
 #define EXTERN_FORCE_RELOC 0
 
+/* If defined, this macro allows control over whether fixups for a
+   given section will be processed when the linkrelax variable is
+   set. Define it to zero and handle things in md_apply_fix instead.*/
+#define TC_LINKRELAX_FIXUP(SEG) 0
+
+/* If this macro returns non-zero, it guarantees that a relocation will be emitted
+   even when the value can be resolved locally. Do that if linkrelax is turned on */
+#define TC_FORCE_RELOCATION(fix)	avr_force_relocation (fix)
+#define TC_FORCE_RELOCATION_SUB_SAME(fix, seg) \
+  (! SEG_NORMAL (seg) || avr_force_relocation (fix))
+extern int avr_force_relocation (struct fix *);
+
 /* Values passed to md_apply_fix don't include the symbol value.  */
 #define MD_APPLY_SYM_VALUE(FIX) 0
 
@@ -169,6 +181,12 @@ extern long md_pcrel_from_section (struct fix *, segT);
       goto SKIP;					     \
     }
 
+/* This macro is evaluated for any fixup with a fx_subsy that
+   fixup_segment cannot reduce to a number.  If the macro returns
+   false an error will be reported. */
+#define TC_VALIDATE_FIX_SUB(fix, seg)   avr_validate_fix_sub (fix)
+extern int avr_validate_fix_sub (struct fix *);
+
 /* This target is buggy, and sets fix size too large.  */
 #define TC_FX_SIZE_SLACK(FIX) 2
 
@@ -190,3 +208,8 @@ extern long md_pcrel_from_section (struct fix *, segT);
 /* Define a hook to setup initial CFI state.  */
 extern void tc_cfi_frame_initial_instructions (void);
 #define tc_cfi_frame_initial_instructions tc_cfi_frame_initial_instructions
+
+/* The difference between same-section symbols may be affected by linker
+   relaxation, so do not resolve such expressions in the assembler.  */
+#define md_allow_local_subtract(l,r,s) avr_allow_local_subtract (l, r, s)
+extern bfd_boolean avr_allow_local_subtract (expressionS *, expressionS *, segT);
diff --git a/gas/testsuite/ChangeLog b/gas/testsuite/ChangeLog
index 61b42dd..30d957d 100644
--- a/gas/testsuite/ChangeLog
+++ b/gas/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2014-04-10  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	* gas/avr/diffreloc_withrelax.d: New testcase.
+	* gas/avr/noreloc_withoutrelax.d: Likewise.
+	* gas/avr/relax.s: Likewise.
+
 2014-04-04  Ilya Tocar  <ilya.tocar@intel.com>
 
 	* gas/i386/i386.exp: Run SE1 tests.
diff --git a/gas/testsuite/gas/avr/diffreloc_withrelax.d b/gas/testsuite/gas/avr/diffreloc_withrelax.d
new file mode 100644
index 0000000..6d5bd2e
--- /dev/null
+++ b/gas/testsuite/gas/avr/diffreloc_withrelax.d
@@ -0,0 +1,16 @@
+#name: AVR DIFF relocs with link relax
+#as: -mmcu=avrxmega2 -mlink-relax
+#source: relax.s
+#objdump: -r
+#target: avr-*-*
+
+.*:     file format elf32-avr
+
+RELOCATION RECORDS FOR \[.text\]:
+OFFSET   TYPE              VALUE 
+00000000 R_AVR_CALL        .text
+
+
+RELOCATION RECORDS FOR \[.data\]:
+OFFSET   TYPE              VALUE 
+00000000 R_AVR_DIFF16      .text\+0x00000004
diff --git a/gas/testsuite/gas/avr/noreloc_withoutrelax.d b/gas/testsuite/gas/avr/noreloc_withoutrelax.d
new file mode 100644
index 0000000..daaaeb2
--- /dev/null
+++ b/gas/testsuite/gas/avr/noreloc_withoutrelax.d
@@ -0,0 +1,11 @@
+#name: AVR no DIFF relocs without link relax
+#as: -mmcu=avrxmega2
+#objdump: -r
+#source: relax.s
+#target: avr-*-*
+
+.*:     file format elf32-avr
+
+RELOCATION RECORDS FOR \[.text\]:
+OFFSET   TYPE              VALUE 
+00000000 R_AVR_CALL        .text
diff --git a/gas/testsuite/gas/avr/relax.s b/gas/testsuite/gas/avr/relax.s
new file mode 100644
index 0000000..dc6b262
--- /dev/null
+++ b/gas/testsuite/gas/avr/relax.s
@@ -0,0 +1,12 @@
+    .file "diffreloc.s"
+.section	.text,"ax",@progbits
+main:
+L1:
+    jmp  L1
+L2:
+.global	x
+	.section .data
+	.type	x, @object
+	.size	x, 2
+x:
+	.word	L2 - L1