gimple_fold: Support COND_LEN_FNMA/COND_LEN_FMS/COND_LEN_FNMS gimple fold

gimple_fold: Support COND_LEN_FNMA/COND_LEN_FMS/COND_LEN_FNMS gimple fold

Hi, Richard and Richi.

Currently, GCC support COND_LEN_FMA for floating-point **NO** -ffast-math.
It's supported in tree-ssa-math-opts.cc. However, GCC failed to support COND_LEN_FNMA/COND_LEN_FMS/COND_LEN_FNMS.

Consider this following case:
  __attribute__ ((noipa)) void ternop_##TYPE (TYPE *__restrict dst,            \
					      TYPE *__restrict a,              \
					      TYPE *__restrict b, int n)       \
  {                                                                            \
    for (int i = 0; i < n; i++)                                                \
      dst[i] -= a[i] * b[i];                                           \
  }

  TEST_TYPE (float)                                                            \

TEST_ALL ()

Gimple IR for RVV:

...
_39 = -vect__8.14_26;
vect__10.16_21 = .COND_LEN_FMA ({ -1, ... }, vect__6.11_30, _39, vect__4.8_34, vect__4.8_34, _46, 0);
...

This is because this following piece of codes in tree-ssa-math-opts.cc:

      if (len)
	fma_stmt
	  = gimple_build_call_internal (IFN_COND_LEN_FMA, 7, cond, mulop1, op2,
					addop, else_value, len, bias);
      else if (cond)
	fma_stmt = gimple_build_call_internal (IFN_COND_FMA, 5, cond, mulop1,
					       op2, addop, else_value);
      else
	fma_stmt = gimple_build_call_internal (IFN_FMA, 3, mulop1, op2, addop);
      gimple_set_lhs (fma_stmt, gimple_get_lhs (use_stmt));
      gimple_call_set_nothrow (fma_stmt, !stmt_can_throw_internal (cfun,
								   use_stmt));
      gsi_replace (&gsi, fma_stmt, true);
      /* Follow all SSA edges so that we generate FMS, FNMA and FNMS
	 regardless of where the negation occurs.  */
      gimple *orig_stmt = gsi_stmt (gsi);
      if (fold_stmt (&gsi, follow_all_ssa_edges))
	{
	  if (maybe_clean_or_replace_eh_stmt (orig_stmt, gsi_stmt (gsi)))
	    gcc_unreachable ();
	  update_stmt (gsi_stmt (gsi));
	}

'fold_stmt' failed to fold NEGATE_EXPR + COND_LEN_FMA ====> COND_LEN_FNMA.

This patch support STMT fold into:

vect__10.16_21 = .COND_LEN_FNMA ({ -1, ... }, vect__8.14_26, vect__6.11_30, vect__4.8_34, { 0.0, ... }, _46, 0);

Note that COND_LEN_FNMA has 7 arguments and COND_LEN_ADD has 6 arguments.

Extend maximum num ops:
-  static const unsigned int MAX_NUM_OPS = 5;
+  static const unsigned int MAX_NUM_OPS = 7;

Bootstrap and Regtest on X86 passed.
Tested on aarch64 Qemu.

Fully tested COND_LEN_FNMA/COND_LEN_FMS/COND_LEN_FNMS on RISC-V backend.

gcc/ChangeLog:

	* genmatch.cc (decision_tree::gen): Support
	COND_LEN_FNMA/COND_LEN_FMS/COND_LEN_FNMS gimple fold.
	* gimple-match-exports.cc (gimple_simplify): Ditto.
	(gimple_resimplify6): New function.
	(gimple_resimplify7): New function.
	(gimple_match_op::resimplify): Support
	COND_LEN_FNMA/COND_LEN_FMS/COND_LEN_FNMS gimple fold.
	(convert_conditional_op): Ditto.
	(build_call_internal): Ditto.
	(try_conditional_simplification): Ditto.
	(gimple_extract): Ditto.
	* gimple-match.h (gimple_match_cond::gimple_match_cond): Ditto.
	* internal-fn.cc (CASE): Ditto.