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CSRRW and CSRRWI always write CSR. CSRRS, CSRRC, CSRRSI and CSRRCI write CSR when RS1 isn't zero. The CSR is read only if the [11:10] bits of CSR address is 0x3. The read-only CSR can not be written by the CSR instructions. gas/ * config/tc-riscv.c (riscv_ip): New boolean insn_with_csr to indicate we are assembling instruction with CSR. Call riscv_csr_read_only_check after parsing all arguments. (enum csr_insn_type): New enum is used to classify the CSR instruction. (riscv_csr_insn_type, riscv_csr_read_only_check): New functions. These are used to check if we write a read-only CSR by the CSR instruction. * testsuite/gas/riscv/priv-reg-fail-read-only-01.s: New testcase. Test all CSR for the read-only CSR checking. * testsuite/gas/riscv/priv-reg-fail-read-only-01.d: Likewise. * testsuite/gas/riscv/priv-reg-fail-read-only-01.l: Likewise. * testsuite/gas/riscv/priv-reg-fail-read-only-02.s: New testcase. Test all CSR instructions for the read-only CSR checking. * testsuite/gas/riscv/priv-reg-fail-read-only-02.d: Likewise. * testsuite/gas/riscv/priv-reg-fail-read-only-02.l: Likewise.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.