RISC-V: Support zicsr and zifencei extension for -march.

 - CSR related instructions and fence instructions has to be splitted from
   baseline ISA, zicsr and zifencei are corresponding sub-extension.

gcc/ChangeLog:

	* common/config/riscv/riscv-common.c (riscv_implied_info):
	d and f implied zicsr.
	(riscv_ext_flag_table): Handle zicsr and zifencei.
	* config/riscv/riscv-opts.h (MASK_ZICSR): New.
	(MASK_ZIFENCEI): Ditto.
	(TARGET_ZICSR): Ditto.
	(TARGET_ZIFENCEI): Ditto.
	* config/riscv/riscv.md (clear_cache): Check TARGET_ZIFENCEI.
	(fence_i): Ditto.
	* config/riscv/riscv.opt (riscv_zi_subext): New.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/arch-8.c: New.
	* gcc.target/riscv/attribute-14.c: Ditto.

1 files changed, 6 insertions, 0 deletions

diff --git a/gcc/common/config/riscv/riscv-common.c b/gcc/common/config/riscv/riscv-common.c
index f5f7be3..ca88ca1 100644
--- a/gcc/common/config/riscv/riscv-common.c
+++ b/gcc/common/config/riscv/riscv-common.c
@@ -57,6 +57,8 @@ struct riscv_implied_info_t
 static const riscv_implied_info_t riscv_implied_info[] =
 {
   {"d", "f"},
+  {"f", "zicsr"},
+  {"d", "zicsr"},
   {NULL, NULL}
 };
 
@@ -812,6 +814,10 @@ static const riscv_ext_flag_table_t riscv_ext_flag_table[] =
   {"f", &gcc_options::x_target_flags, MASK_HARD_FLOAT},
   {"d", &gcc_options::x_target_flags, MASK_DOUBLE_FLOAT},
   {"c", &gcc_options::x_target_flags, MASK_RVC},
+
+  {"zicsr",    &gcc_options::x_riscv_zi_subext, MASK_ZICSR},
+  {"zifencei", &gcc_options::x_riscv_zi_subext, MASK_ZIFENCEI},
+
   {NULL, NULL, 0}
 };