MIPS/GAS: Respect the `insn32' mode in branch relaxation

MIPS/GAS: Respect the `insn32' mode in branch relaxation

Complement:

commit 833794fc12d98139fc33f6b0b85feb03471007b7
Author: Maciej W. Rozycki <macro@linux-mips.org>
Date:   Tue Jun 25 18:02:34 2013 +0000

<https://sourceware.org/ml/binutils/2013-06/msg00104.html>, ("microMIPS
insn32 mode support"), and fix an issue with microMIPS branch relaxation
producing 16-bit instructions in the `insn32' mode.  Use equivalent
32-bit instruction sequences.

	gas/
	* config/tc-mips.c (RELAX_MICROMIPS_ENCODE): Add `insn32' flag.
	(RELAX_MICROMIPS_INSN32): New macro.
	(RELAX_MICROMIPS_UNCOND, RELAX_MICROMIPS_COMPACT)
	(RELAX_MICROMIPS_LINK, RELAX_MICROMIPS_RELAX32)
	(RELAX_MICROMIPS_TOOFAR16, RELAX_MICROMIPS_MARK_TOOFAR16)
	(RELAX_MICROMIPS_CLEAR_TOOFAR16, RELAX_MICROMIPS_TOOFAR32)
	(RELAX_MICROMIPS_MARK_TOOFAR32, RELAX_MICROMIPS_CLEAR_TOOFAR32):
	Shift bits.
	(append_insn): Record `mips_opts.insn32' with relaxed microMIPS
	branches.
	(relaxed_micromips_32bit_branch_length): Handle the `insn32'
	mode.
	(md_convert_frag): Likewise.
	* testsuite/gas/mips/micromips-branch-relax.s: Add `insn32'
	conditionals.
	* testsuite/gas/mips/micromips-branch-relax.l: Update line
	numbers accordingly.
	* testsuite/gas/mips/micromips-branch-relax-pic.l: Likewise.
	* testsuite/gas/mips/micromips-branch-relax-insn32.d: New test.
	* testsuite/gas/mips/micromips-branch-relax-insn32-pic.d: New
	test.
	* testsuite/gas/mips/micromips-branch-relax-insn32.l: New
	stderr output.
	* testsuite/gas/mips/micromips-branch-relax-insn32-pic.l: New
	stderr output.
	* testsuite/gas/mips/mips.exp: Run the new tests.