LoongArch: Optimized some of the symbolic expansion instructions generated...

LoongArch: Optimized some of the symbolic expansion instructions generated during bitwise operations.

There are two mode iterators defined in the loongarch.md:
	(define_mode_iterator GPR [SI (DI "TARGET_64BIT")])
  and
	(define_mode_iterator X [(SI "!TARGET_64BIT") (DI "TARGET_64BIT")])
Replace the mode in the bit arithmetic from GPR to X.

Since the bitwise operation instruction does not distinguish between 64-bit,
32-bit, etc., it is necessary to perform symbolic expansion if the bitwise
operation is less than 64 bits.
The original definition would have generated a lot of redundant symbolic
extension instructions. This problem is optimized with reference to the
implementation of RISCV.

Add this patch spec2017 500.perlbench performance improvement by 1.8%

gcc/ChangeLog:

	* config/loongarch/loongarch.md (one_cmpl<mode>2): Replace GPR with X.
	(*nor<mode>3): Likewise.
	(nor<mode>3): Likewise.
	(*negsi2_extended): New template.
	(*<optab>si3_internal): Likewise.
	(*one_cmplsi2_internal): Likewise.
	(*norsi3_internal): Likewise.
	(*<optab>nsi_internal): Likewise.
	(bytepick_w_<bytepick_imm>_extend): Modify this template according to the
	modified bit operation to make the optimization work.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/sign-extend-bitwise.c: New test.