avoid splitting small constants in bcrli_nottwobits patterns

I have noticed that in the case when we try to clear two bits through a
small constant,
and ZBS is enabled then GCC split it into two "andi" instructions.
For example for the following C code:
  int foo(int a) {
    return a & ~ 0x101;
  }

GCC generates the following:
  foo:
     andi a0,a0,-2
     andi a0,a0,-257
     ret

but should be this one:
  foo:
     andi a0,a0,-258
     ret

This patch solves the mentioned issue.

gcc/ChangeLog
	* config/riscv/bitmanip.md: Updated predicates of bclri<mode>_nottwobits
	and bclridisi_nottwobits patterns.
	* config/riscv/predicates.md: (not_uimm_extra_bit_or_nottwobits): Adjust
	predicate to avoid splitting arith constants.
	(const_nottwobits_not_arith_operand): New predicate.

gcc/testsuite
	* gcc.target/riscv/zbs-bclri-nottwobits.c: New test.

0 files changed, 0 insertions, 0 deletions