On 06/05/2025 09:36, Yangyu Chen wrote:
On 6 May 2025, at 16:01, Alfie Richards <alfie.richa...@arm.com> wrote:
Hello,
I like this idea. I have a couple thoughts to add.
On 05/05/2025 09:46, Yangyu Chen wrote:
On 5 May 2025, at 16:34, Kyrylo Tkachov <ktkac...@nvidia.com> wrote:
On 4 May 2025, at 19:19, Yangyu Chen <c...@cyyself.name> wrote:
Hi everyone,
This patch series introduces support for the target_clones profile
option in GCC. This option enables users to specify target_clones
attributes in a separate file, allowing GCC to generate multiple
versions of the function with different ISA extensions based on the
specified profile. This is achieved using the -ftarget-profile
option.
Interesting idea, but the terminology is confusing as is.
In GCC “profile” usually refers to an execution profile gathered through PGO
instrumentation or perf.
Whereas here I think you use “profile” to mean a “RISC-V profile” which is
something like a set of target architecture extensions?
Thanks,
Kyrill
Sorry for the unclear information. The target profile here refers
to the target_clones attribute for each function. You can find an
example in the second patch.
I was also confused by the naming initially. Maybe something like
"-ffunction-clone-table" instead?
Indeed. I will change that in the next revision.
For instance, we want a function foo to generate default and RISC-V
vector targets, while a function bar should generate default and
zba,zbb targets. The corresponding source code could be as follows:
```
__attribute__((target_clones("default","arch=+v")))
void foo();
__attribute__((target_clones("default","arch=+zba,+zbb")))
void bar();
```
But if we have a target profile, we can describe it as follows in
a separate file:
```
foo:default#arch=+v
bar:default#arch=+zba,+zbb
```
As every function needs the default version it might be nice to make that
implicit. We can then avoid representing and subsequently diagnosing invalid
files. This could then be:
```
foo:arch=+v
bar:arch=+zba,+zbb#+v
```
Great idea! This will make the table simpler.
Additionally, I think ideally the file can express functions disambiguated by
file, signature, and namespace.
I imagine we could use similar syntax to gdb supports?
For example:
```
foo |arch=+v
bar(int, char) |arch=+zba,+zbb
file.C:baz(char) |arch=+zba,+zbb#arch=+v
namespace::qux |arch=+v
```
Also a great idea. However, I think it's not easy to use to implement
it now in GCC. But I would like to accept any further feedback if
we have such a simple API in GCC to do so, or if it will be implemented
by the community.
And something behind this idea is that I'm researching auto-generating
target clones attributes for developers. Only accepting the ASM
name is enough to implement this.
Ah that makes sense, apologies I missed that.
I think accepting the assembler name is good, and solves the overloading
ambiguity issue.
Maybe we can use the pipe '|' instead of ':' in the file format to leave
room for both in future? I think as function name == assembler name in C
and C++ mangled assembler names are necessarily not valid C++ function
names we should be safe to leave that as further expansion? (I’m not
sure about Fortran and other frontends though?)
Kind regards,
Alfie Richards
Thanks,
Yangyu Chen
Thanks,
Alfie Richards
Thanks,
Yangyu Chen
The primary objective of this patch series is to provide a
user-friendly way to specify target_clones attributes without
modifying the source code. This approach enhances the source code's
cleanliness, facilitates easier maintenance, and ensures portability
across different architectures and compiler versions.
The example usage of the target_clones profile option is detailed in
the commit message of the second patch.
I understand that this patch lacks comprehensive documentation and
test cases, as I am still in the process of writing them.
However, I would appreciate feedback on the implementation before
adding them. If the implementation is deemed acceptable, I
will proceed with writing the documentation and test cases.
Yangyu Chen (2):
Fortran: Do not make_decl_rtl in trans_function_start
Add target_clones profile option support
gcc/common.opt | 7 +++++++
gcc/fortran/trans-decl.cc | 3 ---
gcc/multiple_target.cc | 24 +++++++++++++++++++++++-
gcc/opts.cc | 23 +++++++++++++++++++++++
4 files changed, 53 insertions(+), 4 deletions(-)
--
2.49.0
