[PATCH] RISC-V: Add Zvfbfmin extension to the -march= option

[PATCH] RISC-V: Add Zvfbfmin extension to the -march= option

This patch would like to add new sub extension (aka Zvfbfmin) to the
-march= option. It introduces a new data type BF16.

Depending on different usage scenarios, the Zvfbfmin extension may
depend on 'V' or 'Zve32f'. This patch only implements dependencies
in scenario of Embedded Processor. In scenario of Application
Processor, it is necessary to explicitly indicate the dependent
'V' extension.

You can locate more information about Zvfbfmin from below spec doc.

https://github.com/riscv/riscv-bfloat16/releases/download/20231027/riscv-bfloat16.pdf

gcc/ChangeLog:

	* common/config/riscv/riscv-common.cc:
	(riscv_implied_info): Add zvfbfmin item.
	(riscv_ext_version_table): Ditto.
	(riscv_ext_flag_table): Ditto.
	* config/riscv/riscv.opt:
	(MASK_ZVFBFMIN): New macro.
	(MASK_VECTOR_ELEN_BF_16): Ditto.
	(TARGET_ZVFBFMIN): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/arch-31.c: New test.
	* gcc.target/riscv/arch-32.c: New test.
	* gcc.target/riscv/predef-32.c: New test.
	* gcc.target/riscv/predef-33.c: New test.