The goal of this commit is to allow RV64 binaries compiled for the 'F'
extension to run on a target that supports both the 'F' and 'D'
extensions.
The 'D' extension depends on the 'F' extension and chapter 9 of the
RISC-V ISA manual implies that running a program compiled for 'F' on
a 'D' target should be fine.
To support this the gdbarch now holds two feature sets, one represents
the features that are present on the target, and one represents the
features requested in the ELF flags.
The existing error checks are relaxed slightly to allow binaries
compiled for 32-bit 'F' extension to run on targets with the 64-bit
'D' extension.
A new set of functions called riscv_abi_{xlen,flen} are added to
compliment the existing riscv_isa_{xlen,flen}, and some callers to the
isa functions now call the abi functions when that is appropriate.
In riscv_call_arg_struct two asserts are removed, these asserts no
longer make sense. The asserts were both like this:
gdb_assert (TYPE_LENGTH (ainfo->type)
<= (cinfo->flen + cinfo->xlen));
And were made in two cases, when passing structures like these:
struct {
integer field1;
float field2;
};
or,
struct {
float field1;
integer field2;
};
When running on an RV64 target which only has 32-bit float then the
integer field could be 64-bits, while if the float field is 32-bits
the overall size of the structure can be 128-bits (with 32-bits of
padding). In this case the assertion would fail, however, the code
isn't incorrect, so its safe to just remove the assertion.
This was tested by running on an RV64IMFDC target using a compiler
configured for RV64IMFC, and comparing the results with those obtained
when using a compiler configured for RV64IMFDC. The only regressions
I see (now) are in gdb.base/store.exp and are related too different
code generation choices GCC makes between the two targets.
Finally, this commit does not make any attempt to support running
binaries compiled for RV32 on an RV64 target, though nothing in here
should prevent that being supported in the future.
gdb/ChangeLog:
* arch/riscv.h (struct riscv_gdbarch_features) <hw_float_abi>:
Delete.
<operator==>: Update with for removed field.
<hash>: Likewise.
* riscv-tdep.h (struct gdbarch_tdep) <features>: Renamed to...
<isa_features>: ...this.
<abi_features>: New field.
(riscv_isa_flen): Update comment.
(riscv_abi_xlen): New declaration.
(riscv_abi_flen): New declaration.
* riscv-tdep.c (riscv_isa_xlen): Update to get answer from
isa_features.
(riscv_abi_xlen): New function.
(riscv_isa_flen): Update to get answer from isa_features.
(riscv_abi_flen): New function.
(riscv_has_fp_abi): Update to get answer from abi_features.
(riscv_call_info::riscv_call_info): Use abi xlen and flen, not isa
xlen and flen.
(riscv_call_info) <xlen, flen>: Update comment.
(riscv_call_arg_struct): Remove invalid assertions
(riscv_features_from_gdbarch_info): Update now hw_float_abi field
is removed.
(riscv_gdbarch_init): Gather isa features and abi features
separately, ensure both match on the gdbarch when reusing an old
gdbarch. Relax an error check to allow 32-bit abi float to run on
a target with 64-bit float hardware.
This commit applies all changes made after running the gdb/copyright.py
script.
Note that one file was flagged by the script, due to an invalid
copyright header
(gdb/unittests/basic_string_view/element_access/char/empty.cc).
As the file was copied from GCC's libstdc++-v3 testsuite, this commit
leaves this file untouched for the time being; a patch to fix the header
was sent to gcc-patches first.
gdb/ChangeLog:
Update copyright year range in all GDB files.
GDB relies on the fact that if two target descriptions have the same
contents, then they will be the same object instance (having the same
address). One place where this is a requirement is in
GDBARCH_LIST_LOOKUP_BY_INFO which is used to find previously created
gdbarch objects.
In GDBARCH_LIST_LOOKUP_BY_INFO a pointer comparison is made on the
gdbarch's target description, if the pointers are different then it is
assumed the gdbarches have different, non-compatible target
descriptions.
Previously we would create duplicate target descriptions in the belief
that RISCV_GDBARCH_INIT would spot this duplication and discard the
second instance. However, this was incorrect, and instead we ended up
creating duplicate gdbarch objects.
With this commit every unique feature set will create one and only one
target description, the feature set and resulting target description
is then cached so that the same target description object can be
returned later.
Many other target avoid this problem by creating a small number of
named target descriptions, and returning one of these. However, we
currently have 8 possible target descriptions (32 vs 64 bit for x-reg
and f-reg, and h/w or s/w float abi) and creating each of these just
to avoid a dynamic cache seems pointless.
gdb/ChangeLog:
* arch/riscv.h (riscv_gdbarch_features::hash): New method.
* arch/riscv.c (struct riscv_gdbarch_features_hasher): New.
(riscv_tdesc_cache): New global.
(riscv_create_target_description): Look in the cache before
creating a new target description.
Add '==' and '!=' operators for the struct riscv_gdb_features,
allowing a small simplification.
gdb/ChangeLog:
* arch/riscv.h (riscv_gdb_features::operator==): New.
(riscv_gdb_features::operator!=): New.
* riscv-tdep.c (riscv_gdbarch_init): Make use of the inequality
operator.
Makes more of the interface related to fetching target descriptions
constant.
gdb/ChangeLog:
* arch/riscv.h (riscv_create_target_description): Make return type
const.
* arch/riscv.c (riscv_create_target_description): Likewise.
* riscv-tdep.c (riscv_find_default_target_description): Likewise.
This commit adds target description support for riscv.
I've used the split feature approach for specifying the architectural
features, and the CSR feature is auto-generated from the riscv-opc.h
header file.
If the target doesn't provide a suitable target description then GDB
will build one by looking at the bfd headers.
This commit does not implement target description creation for the
Linux or FreeBSD native targets, both of these will need to add
read_description methods into their respective target classes, which
probe the target features, and then call
riscv_create_target_description to build a suitable target
description. Until this is done Linux and FreeBSD will get the same
default target description based on the bfd that bare-metal targets
get.
I've only added feature descriptions for 32 and 64 bit registers, 128
bit registers (for RISC-V) are not supported in the reset of GDB yet.
This commit removes the special reading of the MISA register in order
to establish the target features, this was only used for figuring out
the f-register size, and even that wasn't done consistently. We now
rely on the target to tell us what size of registers it has (or look
in the BFD as a last resort). The result of this is that we should
now support RV64 targets with 32-bit float, though I have not
extensively tested this combination yet.
* Makefile.in (ALL_TARGET_OBS): Add arch/riscv.o.
(HFILES_NO_SRCDIR): Add arch/riscv.h.
* arch/riscv.c: New file.
* arch/riscv.h: New file.
* configure.tgt: Add cpu_obs list of riscv, move riscv-tdep.o into
this list, and add arch/riscv.o.
* features/Makefile: Add riscv features.
* features/riscv/32bit-cpu.c: New file.
* features/riscv/32bit-cpu.xml: New file.
* features/riscv/32bit-csr.c: New file.
* features/riscv/32bit-csr.xml: New file.
* features/riscv/32bit-fpu.c: New file.
* features/riscv/32bit-fpu.xml: New file.
* features/riscv/64bit-cpu.c: New file.
* features/riscv/64bit-cpu.xml: New file.
* features/riscv/64bit-csr.c: New file.
* features/riscv/64bit-csr.xml: New file.
* features/riscv/64bit-fpu.c: New file.
* features/riscv/64bit-fpu.xml: New file.
* features/riscv/rebuild-csr-xml.sh: New file.
* riscv-tdep.c: Add 'arch/riscv.h' include.
(riscv_gdb_reg_names): Delete.
(csr_reggroup): New global.
(struct riscv_register_alias): Delete.
(struct riscv_register_feature): New structure.
(riscv_register_aliases): Delete.
(riscv_xreg_feature): New global.
(riscv_freg_feature): New global.
(riscv_virtual_feature): New global.
(riscv_csr_feature): New global.
(riscv_create_csr_aliases): New function.
(riscv_read_misa_reg): Delete.
(riscv_has_feature): Delete.
(riscv_isa_xlen): Simplify, just return cached xlen.
(riscv_isa_flen): Simplify, just return cached flen.
(riscv_has_fp_abi): Update for changes in struct gdbarch_tdep.
(riscv_register_name): Update to make use of tdesc_register_name.
Look up xreg and freg names in the new globals riscv_xreg_feature
and riscv_freg_feature. Don't supply csr aliases here.
(riscv_fpreg_q_type): Delete.
(riscv_register_type): Use tdesc_register_type in almost all
cases, override the returned type in a few specific cases only.
(riscv_print_one_register_info): Handle errors reading registers.
(riscv_register_reggroup_p): Use tdesc_register_in_reggroup_p for
registers that are otherwise unknown to GDB. Also check the
csr_reggroup.
(riscv_print_registers_info): Remove assert about upper register
number, and use gdbarch_register_reggroup_p instead of
short-cutting.
(riscv_find_default_target_description): New function.
(riscv_check_tdesc_feature): New function.
(riscv_add_reggroups): New function.
(riscv_setup_register_aliases): New function.
(riscv_init_reggroups): New function.
(_initialize_riscv_tdep): Add calls to setup CSR aliases, and
setup register groups. Register new riscv debug variable.
* riscv-tdep.h: Add 'arch/riscv.h' include.
(struct gdbarch_tdep): Remove abi union, and add
riscv_gdbarch_features field. Remove cached quad floating point
type, and provide initialisation for double type field.
* target-descriptions.c (maint_print_c_tdesc_cmd): Add riscv to
the list of targets using the feature based target descriptions.
* NEWS: Mention target description support.
gdb/doc/ChangeLog:
* gdb.texinfo (Standard Target Features): Add RISC-V Features
sub-section.
