MIPS: Add options to control branch ISA checks

Complement commit 9d862524f6ae ("MIPS: Verify the ISA mode and alignment
of branch and jump targets") and add GAS and LD options to control the
checks for invalid branches between ISA modes introduced there, to help
with some handwritten code lacking `.insn' annotation for labels used as
branch targets and code produced by older versions of GCC which suffers
from the issue with branches to code that has been optimized away,
addressed with GCC commit 242424 ("MIPS/GCC: Mark trailing labels with
`.insn'"), <https://gcc.gnu.org/ml/gcc-patches/2016-11/msg01061.html>.

	bfd/
	* elfxx-mips.h (_bfd_mips_elf_insn32): Rename prototype to...
	(_bfd_mips_elf_linker_flags): ... this.  Add another parameter.
	* elfxx-mips.c (mips_elf_link_hash_table): Add
	`ignore_branch_isa' member.
	(mips_elf_perform_relocation): Do not treat an ISA mode mismatch
	in branch relocation calculation as an error if
	`ignore_branch_isa' has been set.
	(_bfd_mips_elf_insn32): Rename to...
	(_bfd_mips_elf_linker_flags): ... this.  Rename the `on'
	parameter to `insn32' and add an `ignore_branch_isa' parameter.
	Handle the new parameter.

	gas/
	* config/tc-mips.c (mips_ignore_branch_isa): New variable.
	(options): Add OPTION_IGNORE_BRANCH_ISA and
	OPTION_NO_IGNORE_BRANCH_ISA enum values.
	(md_longopts): Add "mignore-branch-isa" and
	"mno-ignore-branch-isa" options.
	(md_parse_option): Handle OPTION_IGNORE_BRANCH_ISA and
	OPTION_NO_IGNORE_BRANCH_ISA.
	(fix_bad_cross_mode_branch_p): Return FALSE if
	`mips_ignore_branch_isa' has been set.
	(md_show_usage): Add `-mignore-branch-isa' and
	`-mno-ignore-branch-isa'.

	* doc/as.texinfo (Target MIPS options): Add
	`-mignore-branch-isa' and `-mno-ignore-branch-isa' options.
	(-mignore-branch-isa, -mno-ignore-branch-isa): New options.
	* doc/c-mips.texi (MIPS Options): Add `-mignore-branch-isa' and
	`-mno-ignore-branch-isa' options.

	* testsuite/gas/mips/branch-local-ignore-2.d: New test.
	* testsuite/gas/mips/branch-local-ignore-3.d: New test.
	* testsuite/gas/mips/branch-local-ignore-n32-2.d: New test.
	* testsuite/gas/mips/branch-local-ignore-n32-3.d: New test.
	* testsuite/gas/mips/branch-local-ignore-n64-2.d: New test.
	* testsuite/gas/mips/branch-local-ignore-n64-3.d: New test.
	* testsuite/gas/mips/mips.exp: Run the new tests.

	ld/
	* emultempl/mipself.em (ignore_branch_isa): New variable.
	(mips_create_output_section_statements): Rename
	`_bfd_mips_elf_insn32' called to `_bfd_mips_elf_linker_flags',
	add `ignore_branch_isa' argument.
	(PARSE_AND_LIST_PROLOGUE): Add OPTION_IGNORE_BRANCH_ISA and
	OPTION_NO_IGNORE_BRANCH_ISA enum values.
	(PARSE_AND_LIST_LONGOPTS): Add "ignore-branch-isa" and
	"no-ignore-branch-isa" options.
	(PARSE_AND_LIST_OPTIONS): Add `--ignore-branch-isa' and
	`--no-ignore-branch-isa'.
	(PARSE_AND_LIST_ARGS_CASES): Handle OPTION_IGNORE_BRANCH_ISA and
	OPTION_NO_IGNORE_BRANCH_ISA.

	* ld.texinfo (Options specific to MIPS targets): Add
	`--ignore-branch-isa' and `--no-ignore-branch-isa' options.
	(ld and the MIPS family): Likewise.

	* testsuite/ld-mips-elf/bal-jalx-pic-ignore.d: New test.
	* testsuite/ld-mips-elf/bal-jalx-pic-ignore-n32.d: New test.
	* testsuite/ld-mips-elf/bal-jalx-pic-ignore-n64.d: New test.
	* testsuite/ld-mips-elf/unaligned-branch-ignore-2.d: New test.
	* testsuite/ld-mips-elf/unaligned-branch-ignore-r6-1: New test.
	* testsuite/ld-mips-elf/unaligned-branch-ignore-mips16: New
	test.
	* testsuite/ld-mips-elf/unaligned-branch-ignore-micromips: New
	test.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.

1 files changed, 23 insertions, 2 deletions

diff --git a/ld/emultempl/mipself.em b/ld/emultempl/mipself.em
index 74ede87..cd68707 100644
--- a/ld/emultempl/mipself.em
+++ b/ld/emultempl/mipself.em
@@ -34,6 +34,7 @@ static lang_input_statement_type *stub_file;
 static bfd *stub_bfd;
 
 static bfd_boolean insn32;
+static bfd_boolean ignore_branch_isa;
 
 static void
 mips_after_parse (void)
@@ -202,7 +203,7 @@ mips_create_output_section_statements (void)
 
   htab = elf_hash_table (&link_info);
   if (is_elf_hash_table (htab) && is_mips_elf (link_info.output_bfd))
-    _bfd_mips_elf_insn32 (&link_info, insn32);
+    _bfd_mips_elf_linker_flags (&link_info, insn32, ignore_branch_isa);
 
   if (is_mips_elf (link_info.output_bfd))
     _bfd_mips_elf_init_stubs (&link_info, mips_add_stub_section);
@@ -253,13 +254,17 @@ PARSE_AND_LIST_PROLOGUE='
 enum
   {
     OPTION_INSN32 = 301,
-    OPTION_NO_INSN32
+    OPTION_NO_INSN32,
+    OPTION_IGNORE_BRANCH_ISA,
+    OPTION_NO_IGNORE_BRANCH_ISA
   };
 '
 
 PARSE_AND_LIST_LONGOPTS='
   { "insn32", no_argument, NULL, OPTION_INSN32 },
   { "no-insn32", no_argument, NULL, OPTION_NO_INSN32 },
+  { "ignore-branch-isa", no_argument, NULL, OPTION_IGNORE_BRANCH_ISA },
+  { "no-ignore-branch-isa", no_argument, NULL, OPTION_NO_IGNORE_BRANCH_ISA },
 '
 
 PARSE_AND_LIST_OPTIONS='
@@ -269,6 +274,14 @@ PARSE_AND_LIST_OPTIONS='
   fprintf (file, _("\
   --no-insn32                 Generate all microMIPS instructions\n"
 		   ));
+  fprintf (file, _("\
+  --ignore-branch-isa         Accept invalid branch relocations requiring\n\
+                              an ISA mode switch\n"
+		   ));
+  fprintf (file, _("\
+  --no-ignore-branch-isa      Reject invalid branch relocations requiring\n\
+                              an ISA mode switch\n"
+		   ));
 '
 
 PARSE_AND_LIST_ARGS_CASES='
@@ -279,6 +292,14 @@ PARSE_AND_LIST_ARGS_CASES='
     case OPTION_NO_INSN32:
       insn32 = FALSE;
       break;
+
+    case OPTION_IGNORE_BRANCH_ISA:
+      ignore_branch_isa = TRUE;
+      break;
+
+    case OPTION_NO_IGNORE_BRANCH_ISA:
+      ignore_branch_isa = FALSE;
+      break;
 '
 
 LDEMUL_AFTER_PARSE=mips_after_parse