RISC-V: Support rounding mode for VFMADD/VFMACC autovec

There will be a case like below for intrinsic and autovec combination

vfadd RTZ   <- intrinisc static rounding
vfmadd      <- autovec/autovec-opt

The autovec generated vfmadd should take DYN mode, and the
frm must be restored before the vfmadd insn. This patch
would like to fix this issue by:

* Add the frm operand to the vfmadd/vfmacc autovec/autovec-opt pattern.
* Set the frm_mode attr to DYN.

Thus, the frm flow when combine autovec and intrinsic should be.

+------------
| frrm  a5
| ...
| fsrmi 4
| vfadd       <- intrinsic static rounding.
| ...
| fsrm  a5
| vfmadd      <- autovec/autovec-opt
| ...
+------------

However, we leverage unspec instead of use to consume the FRM register
because there are some restrictions from the combine pass. Some code
path of try_combine may require the XVECLEN(pat, 0) == 2 for the
recog_for_combine, and add new use will make the XVECLEN(pat, 0) == 3
and result in the vfwmacc optimization failure. For example, in the
test  widen-complicate-5.c and widen-8.c

Finally, there will be other fma cases and they will be covered in
the underlying patches.

Signed-off-by: Pan Li <pan2.li@intel.com>
Co-Authored-By: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>

gcc/ChangeLog:

	* config/riscv/autovec-opt.md: Add FRM_REGNUM to vfmadd/vfmacc.
	* config/riscv/autovec.md: Ditto.
	* config/riscv/vector-iterators.md: Add UNSPEC_VFFMA.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/float-point-frm-autovec-1.c: New test.

0 files changed, 0 insertions, 0 deletions