RISC-V: Add CSRs for T-Head VECTOR vendor extension

T-Head has a range of vendor-specific instructions.
Therefore it makes sense to group them into smaller chunks
in form of vendor extensions.

This patch adds the CSRs for XTheadVector. Because of the
conflict between encoding and teh 'V' extension, it is implemented
by alias. The 'th' prefix and the "XTheadVector" extension are
documented in a PR for the RISC-V toolchain conventions ([1]).

[1] https://github.com/riscv-non-isa/riscv-toolchain-conventions/pull/19

Co-developed-by: Lifang Xia <lifang_xia@linux.alibaba.com>
Co-developed-by: Christoph Müllner <christoph.muellner@vrull.eu>

gas/ChangeLog:

	* config/tc-riscv.c (enum riscv_csr_class): Add the class for
	the CSRs of the "XTheadVector" extension.
	(riscv_csr_address): Likewise.
	* testsuite/gas/riscv/x-thead-vector-csr-warn.d: New test.
	* testsuite/gas/riscv/x-thead-vector-csr-warn.l: New test.
	* testsuite/gas/riscv/x-thead-vector-csr.d: New test.
	* testsuite/gas/riscv/x-thead-vector-csr.s: New test.

include/ChangeLog:

	* opcode/riscv-opc.h (DECLARE_CSR_ALIAS): Likewise.

opcodes/ChangeLog:

	* riscv-dis.c (print_insn_args): Prefix the CSRs disassembly with 'th'.

5 files changed, 57 insertions, 0 deletions

diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 402c46a..af9a34a 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -91,6 +91,7 @@ enum riscv_csr_class
   CSR_CLASS_SSTC_AND_H,		/* Sstc only (with H) */
   CSR_CLASS_SSTC_32,		/* Sstc RV32 only */
   CSR_CLASS_SSTC_AND_H_32,	/* Sstc RV32 only (with H) */
+  CSR_CLASS_XTHEADVECTOR,	/* xtheadvector only */
 };
 
 /* This structure holds all restricted conditions for a CSR.  */
@@ -1104,6 +1105,9 @@ riscv_csr_address (const char *csr_name,
       break;
     case CSR_CLASS_DEBUG:
       break;
+    case CSR_CLASS_XTHEADVECTOR:
+      extension = "xtheadvector";
+      break;
     default:
       as_bad (_("internal: bad RISC-V CSR class (0x%x)"), csr_class);
     }
diff --git a/gas/testsuite/gas/riscv/x-thead-vector-csr-warn.d b/gas/testsuite/gas/riscv/x-thead-vector-csr-warn.d
new file mode 100644
index 0000000..17c707d
--- /dev/null
+++ b/gas/testsuite/gas/riscv/x-thead-vector-csr-warn.d
@@ -0,0 +1,3 @@
+#as: -march=rv64gc -mcsr-check
+#source: x-thead-vector-csr.s
+#warning_output: x-thead-vector-csr-warn.l
diff --git a/gas/testsuite/gas/riscv/x-thead-vector-csr-warn.l b/gas/testsuite/gas/riscv/x-thead-vector-csr-warn.l
new file mode 100644
index 0000000..4dd867c
--- /dev/null
+++ b/gas/testsuite/gas/riscv/x-thead-vector-csr-warn.l
@@ -0,0 +1,16 @@
+.*Assembler messages:
+.*Warning: invalid CSR `th.vstart', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vxsat', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vxrm', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vl', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vtype', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vlenb', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vstart', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vxsat', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vxrm', needs `xtheadvector' extension
+.*Warning: invalid CSR `th.vl', needs `xtheadvector' extension
+.*Warning: read-only CSR is written `csrw th.vl,a0'
+.*Warning: invalid CSR `th.vtype', needs `xtheadvector' extension
+.*Warning: read-only CSR is written `csrw th.vtype,a0'
+.*Warning: invalid CSR `th.vlenb', needs `xtheadvector' extension
+.*Warning: read-only CSR is written `csrw th.vlenb,a0'
\ No newline at end of file
diff --git a/gas/testsuite/gas/riscv/x-thead-vector-csr.d b/gas/testsuite/gas/riscv/x-thead-vector-csr.d
new file mode 100644
index 0000000..75357b2
--- /dev/null
+++ b/gas/testsuite/gas/riscv/x-thead-vector-csr.d
@@ -0,0 +1,21 @@
+#as: -march=rv32if_xtheadvector
+#objdump: -dr
+
+.*:[ 	]+file format .*
+
+
+Disassembly of section .text:
+
+0+000 <.text>:
+[ 	]+[0-9a-f]+:[ 	]+00802573[ 	]+csrr[ 	]+a0,th.vstart
+[ 	]+[0-9a-f]+:[ 	]+00902573[ 	]+csrr[ 	]+a0,th.vxsat
+[ 	]+[0-9a-f]+:[ 	]+00a02573[ 	]+csrr[ 	]+a0,th.vxrm
+[ 	]+[0-9a-f]+:[ 	]+c2002573[ 	]+csrr[ 	]+a0,th.vl
+[ 	]+[0-9a-f]+:[ 	]+c2102573[ 	]+csrr[ 	]+a0,th.vtype
+[ 	]+[0-9a-f]+:[ 	]+c2202573[ 	]+csrr[ 	]+a0,th.vlenb
+[ 	]+[0-9a-f]+:[ 	]+00851073[ 	]+csrw[ 	]+th.vstart,a0
+[ 	]+[0-9a-f]+:[ 	]+00951073[ 	]+csrw[ 	]+th.vxsat,a0
+[ 	]+[0-9a-f]+:[ 	]+00a51073[ 	]+csrw[ 	]+th.vxrm,a0
+[ 	]+[0-9a-f]+:[ 	]+c2051073[ 	]+csrw[ 	]+th.vl,a0
+[ 	]+[0-9a-f]+:[ 	]+c2151073[ 	]+csrw[ 	]+th.vtype,a0
+[ 	]+[0-9a-f]+:[ 	]+c2251073[ 	]+csrw[ 	]+th.vlenb,a0
diff --git a/gas/testsuite/gas/riscv/x-thead-vector-csr.s b/gas/testsuite/gas/riscv/x-thead-vector-csr.s
new file mode 100644
index 0000000..e11f87f
--- /dev/null
+++ b/gas/testsuite/gas/riscv/x-thead-vector-csr.s
@@ -0,0 +1,13 @@
+	csrr a0, th.vstart
+	csrr a0, th.vxsat
+	csrr a0, th.vxrm
+	csrr a0, th.vl
+	csrr a0, th.vtype
+	csrr a0, th.vlenb
+
+	csrw th.vstart, a0
+	csrw th.vxsat, a0
+	csrw th.vxrm, a0
+	csrw th.vl, a0		# read-only CSR
+	csrw th.vtype, a0	# read-only CSR
+	csrw th.vlenb, a0	# read-only CSR