binutils-gdb modified for the FreeChainXenon project
ed69cbc8ef
First, consider the RISC-V register $x1. This register has an alias $ra. When GDB processes an incoming target description we allow the target to use either register name to describe the target. However, within GDB's UI we want to use the $ra alias in preference to the $x1 architecture name. To achieve this GDB overrides the tdesc_register_name callback with riscv_register_name. In riscv_register_name we ensure that we always return the preferred name, so in this case "ra". To ensure the user can still access the register as $x1 if they want to, when in riscv_check_tdesc_feature we spot that the target has supplied the register, we add aliases for every name except the preferred one, so in this case we add the alias "x1". This scheme seems to work quite well, the targets have the flexibility to be architecture focused if they wish (using x0 - x31) while GDB is still using the ABI names ra, sp, gp, etc. When this code was originally added there was an attempt made to include the CSRs in the same scheme. At the time the CSRs only had two names, one pulled from riscv-opc.h, and one generated in GDB that had the pattern csr%d. The idea was that if the remote targets description described the CSRs as csr%d then GDB would rename these back to the real CSR name. This code was only included because if followed the same pattern as the x-regs and f-regs, not because I was actually aware of any target that did this. However, recent changes to add additional CSR aliases has made me rethink the position here. Lets consider the CSR $dscratch0. This register has an alias 'csr1970' (1970 is 0x7b2, which is the offset of the CSR register into the CSR address space). However, this register was originally called just 'dscratch', and so, after recent commits, this register also has the alias 'dscratch'. As the riscv-opc.h file calls this register 'dscratch0' GDB's preferred name for this register is 'dscratch0'. So, if the remote target description includes the register 'dscratch0', then GDB will add the aliases 'dscratch', and 'csr1970'. In the UI GDB will describe the register as 'dscratch0', and all it good. The problem I see in this case is where the target describes the register as 'dscratch'. In this case GDB will still spot the register and add the aliases 'dscratch', and 'csr1970', GDB will then give the register the preferred name 'dscratch0'. I don't like this. For the CSRs I think that we should stick with the naming scheme offered by the remote target description. As the RISC-V specification evolves and CSR register names evolve, insisting on referring to registers by the most up to date name makes it harder for a target to provide a consistent target description for an older version of the RISC-V architecture spec. In this precise case the target offers 'dscratch', which is from an older version of the RISC-V specification, the newer version of the spec has two registers 'dscratch0' and 'dscratch1'. If we insist on using 'dscratch0' it is then a little "weird" (or seems so to me) when 'dscratch1' is missing. This patch makes a distinction between the x and f registers and the other register sets. For x and f we still make use of the renaming scheme, forcing GDB to prefer the ABI name. But after this patch the CSR register group, and also the virtual register group, will always prefer to use the name given in the target description, adding other names as aliases, but not making any other name the preferred name. gdb/ChangeLog: * riscv-tdep.c (struct riscv_register_feature::register_info): Fix whitespace error for declaration of names member variable. (struct riscv_register_feature): Add new prefer_first_name member variable, and fix whitespace error in declaration of registers. (riscv_xreg_feature): Initialize prefer_first_name field. (riscv_freg_feature): Likewise. (riscv_virtual_feature): Likewise. (riscv_csr_feature): Likewise. (riscv_register_name): Expand on comments. Remove register name modifications for CSR and virtual registers. gdb/testsuite/ChangeLog: * gdb.arch/riscv-tdesc-regs.exp: Extend test case. |
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| cpu | ||
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| gas | ||
| gdb | ||
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| gdbsupport | ||
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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.