Relocatable read-only section support for absolute jump table

This patch puts absolute jump tables into a relocatable read-only section
if they are on ELF target and relocation is supported.

gcc/ChangeLog:

	* final.c (final_scan_insn_1): Set jump table relocatable as the
	second argument of targetm.asm_out.function_rodata_section.
	* output.h (default_function_rodata_section,
	default_no_function_rodata_section): Add the second argument to the
	declarations.
	* target.def (function_rodata_section): Change the doc and add
	the second argument.
	* doc/tm.texi: Regenerate.
	* varasm.c (jumptable_relocatable): Implement.
	(default_function_rodata_section): Add the second argument
	and the support for relocatable read only sections.
	(default_no_function_rodata_section): Add the second argument.
	(function_mergeable_rodata_prefix): Set the second argument to false.
	* config/mips/mips.c (mips_function_rodata_section): Add the second
	arugment and set it to false.
	* config/s390/s390.c (targetm.asm_out.function_rodata_section): Set
	the second argument to false.
	* config/s390/s390.md: Likewise.

gcc/config/mips/mips.c

@@ -9315,10 +9315,10 @@ mips_select_rtx_section (machine_mode mode, rtx x,
    default_function_rodata_section.  */
 
 static section *
-mips_function_rodata_section (tree decl)
+mips_function_rodata_section (tree decl, bool)
 {
   if (!TARGET_ABICALLS || TARGET_ABSOLUTE_ABICALLS || TARGET_GPWORD)
-    return default_function_rodata_section (decl);
+    return default_function_rodata_section (decl, false);
 
   if (decl && DECL_SECTION_NAME (decl))
     {

gcc/config/s390/s390.c

@@ -11746,7 +11746,7 @@ s390_output_split_stack_data (rtx parm_block, rtx call_done,
   rtx ops[] = { parm_block, call_done };
 
   switch_to_section (targetm.asm_out.function_rodata_section
-		     (current_function_decl));
+		     (current_function_decl, false));
 
   if (TARGET_64BIT)
     output_asm_insn (".align\t8", NULL);

gcc/config/s390/s390.md

@@ -11290,7 +11290,7 @@
   ""
 {
   switch_to_section (targetm.asm_out.function_rodata_section
-		 (current_function_decl));
+		 (current_function_decl, false));
   return "";
 }
   [(set_attr "length" "0")])

gcc/doc/tm.texi

@@ -7711,13 +7711,14 @@ example, the function @code{foo} would be placed in @code{.text.foo}.
 Whatever the actual target object format, this is often good enough.
 @end deftypefn
 
-@deftypefn {Target Hook} {section *} TARGET_ASM_FUNCTION_RODATA_SECTION (tree @var{decl})
-Return the readonly data section associated with
-@samp{DECL_SECTION_NAME (@var{decl})}.
+@deftypefn {Target Hook} {section *} TARGET_ASM_FUNCTION_RODATA_SECTION (tree @var{decl}, bool @var{relocatable})
+Return the readonly data or reloc readonly data section associated with
+@samp{DECL_SECTION_NAME (@var{decl})}. @var{relocatable} selects the latter
+over the former.
 The default version of this function selects @code{.gnu.linkonce.r.name} if
 the function's section is @code{.gnu.linkonce.t.name}, @code{.rodata.name}
-if function is in @code{.text.name}, and the normal readonly-data section
-otherwise.
+or @code{.data.rel.ro.name} if function is in @code{.text.name}, and
+the normal readonly-data or reloc readonly data section otherwise.
 @end deftypefn
 
 @deftypevr {Target Hook} {const char *} TARGET_ASM_MERGEABLE_RODATA_PREFIX

gcc/final.c

@@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "rtl-iter.h"
 #include "print-rtl.h"
 #include "function-abi.h"
+#include "common/common-target.h"
 
 #ifdef XCOFF_DEBUGGING_INFO
 #include "xcoffout.h"		/* Needed for external data declarations.  */
@@ -2154,6 +2155,21 @@ asm_show_source (const char *filename, int linenum)
   fputc ('\n', asm_out_file);
 }
 
+/* Judge if an absolute jump table is relocatable.  */
+
+bool
+jumptable_relocatable (void)
+{
+  bool relocatable = false;
+
+  if (!CASE_VECTOR_PC_RELATIVE
+      && !targetm.asm_out.generate_pic_addr_diff_vec ()
+      && targetm_common.have_named_sections)
+     relocatable = targetm.asm_out.reloc_rw_mask ();
+
+  return relocatable;
+}
+
 /* The final scan for one insn, INSN.
    Args are same as in `final', except that INSN
    is the insn being scanned.
@@ -2493,7 +2509,8 @@ final_scan_insn_1 (rtx_insn *insn, FILE *file, int optimize_p ATTRIBUTE_UNUSED,
 	      int log_align;
 
 	      switch_to_section (targetm.asm_out.function_rodata_section
-				 (current_function_decl));
+				 (current_function_decl,
+				  jumptable_relocatable ()));
 
 #ifdef ADDR_VEC_ALIGN
 	      log_align = ADDR_VEC_ALIGN (table);
@@ -2572,7 +2589,8 @@ final_scan_insn_1 (rtx_insn *insn, FILE *file, int optimize_p ATTRIBUTE_UNUSED,
 
 	    if (! JUMP_TABLES_IN_TEXT_SECTION)
 	      switch_to_section (targetm.asm_out.function_rodata_section
-				 (current_function_decl));
+				 (current_function_decl,
+				  jumptable_relocatable ()));
 	    else
 	      switch_to_section (current_function_section ());
 

gcc/output.h

@@ -572,8 +572,8 @@ extern void default_ctor_section_asm_out_constructor (rtx, int);
 extern section *default_select_section (tree, int, unsigned HOST_WIDE_INT);
 extern section *default_elf_select_section (tree, int, unsigned HOST_WIDE_INT);
 extern void default_unique_section (tree, int);
-extern section *default_function_rodata_section (tree);
-extern section *default_no_function_rodata_section (tree);
+extern section *default_function_rodata_section (tree, bool);
+extern section *default_no_function_rodata_section (tree, bool);
 extern section *default_clone_table_section (void);
 extern section *default_select_rtx_section (machine_mode, rtx,
 					    unsigned HOST_WIDE_INT);

gcc/target.def

@@ -559,16 +559,18 @@ Whatever the actual target object format, this is often good enough.",
  void, (tree decl, int reloc),
  default_unique_section)
 
-/* Return the readonly data section associated with function DECL.  */
+/* Return the readonly data or relocated readonly data section
+   associated with function DECL.  */
 DEFHOOK
 (function_rodata_section,
- "Return the readonly data section associated with\n\
-@samp{DECL_SECTION_NAME (@var{decl})}.\n\
+ "Return the readonly data or reloc readonly data section associated with\n\
+@samp{DECL_SECTION_NAME (@var{decl})}. @var{relocatable} selects the latter\n\
+over the former.\n\
 The default version of this function selects @code{.gnu.linkonce.r.name} if\n\
 the function's section is @code{.gnu.linkonce.t.name}, @code{.rodata.name}\n\
-if function is in @code{.text.name}, and the normal readonly-data section\n\
-otherwise.",
- section *, (tree decl),
+or @code{.data.rel.ro.name} if function is in @code{.text.name}, and\n\
+the normal readonly-data or reloc readonly data section otherwise.",
+ section *, (tree decl, bool relocatable),
  default_function_rodata_section)
 
 /* Nonnull if the target wants to override the default ".rodata" prefix

gcc/varasm.c

@@ -732,12 +732,26 @@ switch_to_other_text_partition (void)
   switch_to_section (current_function_section ());
 }
 
-/* Return the read-only data section associated with function DECL.  */
+/* Return the read-only or relocated read-only data section
+   associated with function DECL.  */
 
 section *
-default_function_rodata_section (tree decl)
+default_function_rodata_section (tree decl, bool relocatable)
 {
-  if (decl != NULL_TREE && DECL_SECTION_NAME (decl))
+  const char* sname;
+  unsigned int flags;
+
+  flags = 0;
+
+  if (relocatable)
+    {
+      sname = ".data.rel.ro.local";
+      flags = (SECTION_WRITE | SECTION_RELRO);
+    }
+  else
+    sname = ".rodata";
+
+  if (decl && DECL_SECTION_NAME (decl))
     {
       const char *name = DECL_SECTION_NAME (decl);
 
@@ -750,37 +764,55 @@ default_function_rodata_section (tree decl)
 	  dot = strchr (name + 1, '.');
 	  if (!dot)
 	    dot = name;
-	  len = strlen (dot) + 8;
+	  len = strlen (dot) + strlen (sname) + 1;
 	  rname = (char *) alloca (len);
 
-	  strcpy (rname, ".rodata");
+	  strcpy (rname, sname);
 	  strcat (rname, dot);
-	  return get_section (rname, SECTION_LINKONCE, decl);
+	  return get_section (rname, (SECTION_LINKONCE | flags), decl);
 	}
-      /* For .gnu.linkonce.t.foo we want to use .gnu.linkonce.r.foo.  */
+      /* For .gnu.linkonce.t.foo we want to use .gnu.linkonce.r.foo or
+	 .gnu.linkonce.d.rel.ro.local.foo if the jump table is relocatable.  */
       else if (DECL_COMDAT_GROUP (decl)
 	       && strncmp (name, ".gnu.linkonce.t.", 16) == 0)
 	{
-	  size_t len = strlen (name) + 1;
-	  char *rname = (char *) alloca (len);
+	  size_t len;
+	  char *rname;
+
+	  if (relocatable)
+	    {
+	      len = strlen (name) + strlen (".rel.ro.local") + 1;
+	      rname = (char *) alloca (len);
+
+	      strcpy (rname, ".gnu.linkonce.d.rel.ro.local");
+	      strcat (rname, name + 15);
+	    }
+	  else
+	    {
+	      len = strlen (name) + 1;
+	      rname = (char *) alloca (len);
 
 	      memcpy (rname, name, len);
 	      rname[14] = 'r';
-	  return get_section (rname, SECTION_LINKONCE, decl);
+	    }
+	  return get_section (rname, (SECTION_LINKONCE | flags), decl);
 	}
       /* For .text.foo we want to use .rodata.foo.  */
       else if (flag_function_sections && flag_data_sections
 	       && strncmp (name, ".text.", 6) == 0)
 	{
 	  size_t len = strlen (name) + 1;
-	  char *rname = (char *) alloca (len + 2);
+	  char *rname = (char *) alloca (len + strlen (sname) - 5);
 
-	  memcpy (rname, ".rodata", 7);
-	  memcpy (rname + 7, name + 5, len - 5);
-	  return get_section (rname, 0, decl);
+	  memcpy (rname, sname, strlen (sname));
+	  memcpy (rname + strlen (sname), name + 5, len - 5);
+	  return get_section (rname, flags, decl);
 	}
     }
 
+  if (relocatable)
+    return get_section (sname, flags, decl);
+  else
     return readonly_data_section;
 }
 
@@ -789,7 +821,7 @@ default_function_rodata_section (tree decl)
    readonly data section.  */
 
 section *
-default_no_function_rodata_section (tree decl ATTRIBUTE_UNUSED)
+default_no_function_rodata_section (tree, bool)
 {
   return readonly_data_section;
 }
@@ -799,7 +831,8 @@ default_no_function_rodata_section (tree decl ATTRIBUTE_UNUSED)
 static const char *
 function_mergeable_rodata_prefix (void)
 {
-  section *s = targetm.asm_out.function_rodata_section (current_function_decl);
+  section *s = targetm.asm_out.function_rodata_section (current_function_decl,
+							false);
   if (SECTION_STYLE (s) == SECTION_NAMED)
     return s->named.name;
   else