Re: [PATCH] libgccjit: Add support for `restrict` attribute on function parameters

[Guillaume Gomez <guillaume1.gomez@gmail.com>]

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Quick question: do you plan to make the merge or should I ask Antoni?

Le jeu. 17 août 2023 à 17:59, Guillaume Gomez <guillaume1.gomez@gmail.com>
a écrit :

> Thanks for the review!
>
> Le jeu. 17 août 2023 à 17:50, David Malcolm <dmalcolm@redhat.com> a écrit
> :
> >
> > On Thu, 2023-08-17 at 17:41 +0200, Guillaume Gomez wrote:
> > > And now I just discovered that a lot of commits from Antoni's fork
> > > haven't been sent upstream which is why the ABI count is so high in
> > > his repository. Fixed that as well.
> >
> > Thanks for the updated patch; I was about to comment on that.
> >
> > This version is good for gcc trunk.
> >
> > Dave
> >
> > >
> > > Le jeu. 17 août 2023 à 17:26, Guillaume Gomez
> > > <guillaume1.gomez@gmail.com> a écrit :
> > > >
> > > > Antoni spot a typo I made:
> > > >
> > > > I added `LIBGCCJIT_HAVE_gcc_jit_type_get_size` instead of
> > > > `LIBGCCJIT_HAVE_gcc_jit_type_get_restrict`. Fixed in this patch,
> > > > sorry
> > > > for the noise.
> > > >
> > > > Le jeu. 17 août 2023 à 11:30, Guillaume Gomez
> > > > <guillaume1.gomez@gmail.com> a écrit :
> > > > >
> > > > > Hi Dave,
> > > > >
> > > > > > What kind of testing has the patch had? (e.g. did you run "make
> > > > > > check-
> > > > > > jit" ?  Has this been in use on real Rust code?)
> > > > >
> > > > > I tested it as Rust backend directly on this code:
> > > > >
> > > > > ```
> > > > > pub fn foo(a: &mut i32, b: &mut i32, c: &i32) {
> > > > >     *a += *c;
> > > > >     *b += *c;
> > > > > }
> > > > > ```
> > > > >
> > > > > I ran it with `rustc` (and the GCC backend) with the following
> > > > > flags:
> > > > > `-C link-args=-lc --emit=asm -O --crate-type=lib` which gave the
> > > > > diff
> > > > > you can see in the attached file. Explanations: the diff on the
> > > > > right
> > > > > has the `__restrict__` attribute used whereas on the left it is
> > > > > the
> > > > > current version where we don't handle it.
> > > > >
> > > > > As for C testing, I used this code:
> > > > >
> > > > > ```
> > > > > void t(int *__restrict__ a, int *__restrict__ b, char
> > > > > *__restrict__ c) {
> > > > >     *a += *c;
> > > > >     *b += *c;
> > > > > }
> > > > > ```
> > > > >
> > > > > (without the `__restrict__` of course when I need to have a
> > > > > witness
> > > > > ASM). I attached the diff as well, this time the file with the
> > > > > use of
> > > > > `__restrict__` in on the left. I compiled with the following
> > > > > flags:
> > > > > `-S -O3`.
> > > > >
> > > > > > Please add a feature macro:
> > > > > > #define LIBGCCJIT_HAVE_gcc_jit_type_get_restrict
> > > > > > (see the similar ones in the header).
> > > > >
> > > > > I added `LIBGCCJIT_HAVE_gcc_jit_type_get_size` and extended the
> > > > > documentation as well to mention the ABI change.
> > > > >
> > > > > > Please add a new ABI tag (LIBGCCJIT_ABI_25 ?), rather than
> > > > > > adding this
> > > > > > to ABI_0.
> > > > >
> > > > > I added `LIBGCCJIT_ABI_34` as `LIBGCCJIT_ABI_33` was the last
> > > > > one.
> > > > >
> > > > > > This refers to a "cold attribute"; is this a vestige of a copy-
> > > > > > and-
> > > > > > paste from a different test case?
> > > > >
> > > > > It is a vestige indeed... Missed this one.
> > > > >
> > > > > > I see that the test scans the generated assembler.  Does the
> > > > > > test
> > > > > > actually verify that restrict has an effect, or was that
> > > > > > another
> > > > > > vestige from a different test case?
> > > > >
> > > > > No, this time it's what I wanted. Please see the C diff I
> > > > > provided
> > > > > above to see that the ASM has a small diff that allowed me to
> > > > > confirm
> > > > > that the `__restrict__` attribute was correctly set.
> > > > >
> > > > > > If this test is meant to run at -O3 and thus can't be part of
> > > > > > test-
> > > > > > combination.c, please add a comment about it to
> > > > > > gcc/testsuite/jit.dg/all-non-failing-tests.h (in the
> > > > > > alphabetical
> > > > > > place).
> > > > >
> > > > > Below `-O3`, this ASM difference doesn't appear unfortunately.
> > > > >
> > > > > > The patch also needs to add documentation for the new
> > > > > > entrypoint (in
> > > > > > topics/types.rst), and for the new ABI tag (in
> > > > > > topics/compatibility.rst).
> > > > >
> > > > > Added!
> > > > >
> > > > > > Thanks again for the patch; hope the above is constructive
> > > > >
> > > > > It was incredibly useful! Thanks for taking time to writing down
> > > > > the
> > > > > explanations.
> > > > >
> > > > > The new patch is attached to this email.
> > > > >
> > > > > Cordially.
> > > > >
> > > > > Le jeu. 17 août 2023 à 01:06, David Malcolm <dmalcolm@redhat.com>
> > > > > a écrit :
> > > > > >
> > > > > > On Wed, 2023-08-16 at 22:06 +0200, Guillaume Gomez via Jit
> > > > > > wrote:
> > > > > > > My apologies, forgot to run the commit checkers. Here's the
> > > > > > > commit
> > > > > > > with the errors fixed.
> > > > > > >
> > > > > > > Le mer. 16 août 2023 à 18:32, Guillaume Gomez
> > > > > > > <guillaume1.gomez@gmail.com> a écrit :
> > > > > > > >
> > > > > > > > Hi,
> > > > > >
> > > > > > Hi Guillaume, thanks for the patch.
> > > > > >
> > > > > > > >
> > > > > > > > This patch adds the possibility to specify the __restrict__
> > > > > > > > attribute
> > > > > > > > for function parameters. It is used by the Rust GCC
> > > > > > > > backend.
> > > > > >
> > > > > > What kind of testing has the patch had? (e.g. did you run "make
> > > > > > check-
> > > > > > jit" ?  Has this been in use on real Rust code?)
> > > > > >
> > > > > > Overall, this patch looks close to being ready, but some nits
> > > > > > below...
> > > > > >
> > > > > > [...]
> > > > > >
> > > > > > > diff --git a/gcc/jit/libgccjit.h b/gcc/jit/libgccjit.h
> > > > > > > index 60eaf39bff6..2e0d08a06d8 100644
> > > > > > > --- a/gcc/jit/libgccjit.h
> > > > > > > +++ b/gcc/jit/libgccjit.h
> > > > > > > @@ -635,6 +635,10 @@ gcc_jit_type_get_const (gcc_jit_type
> > > > > > > *type);
> > > > > > >  extern gcc_jit_type *
> > > > > > >  gcc_jit_type_get_volatile (gcc_jit_type *type);
> > > > > > >
> > > > > > > +/* Given type "T", get type "restrict T".  */
> > > > > > > +extern gcc_jit_type *
> > > > > > > +gcc_jit_type_get_restrict (gcc_jit_type *type);
> > > > > > > +
> > > > > > >  #define LIBGCCJIT_HAVE_SIZED_INTEGERS
> > > > > > >
> > > > > > >  /* Given types LTYPE and RTYPE, return non-zero if they are
> > > > > > compatible.
> > > > > >
> > > > > > Please add a feature macro:
> > > > > > #define LIBGCCJIT_HAVE_gcc_jit_type_get_restrict
> > > > > > (see the similar ones in the header).
> > > > > >
> > > > > > > diff --git a/gcc/jit/libgccjit.map b/gcc/jit/libgccjit.map
> > > > > > > index e52de0057a5..b7289b13845 100644
> > > > > > > --- a/gcc/jit/libgccjit.map
> > > > > > > +++ b/gcc/jit/libgccjit.map
> > > > > > > @@ -104,6 +104,7 @@ LIBGCCJIT_ABI_0
> > > > > > >      gcc_jit_type_as_object;
> > > > > > >      gcc_jit_type_get_const;
> > > > > > >      gcc_jit_type_get_pointer;
> > > > > > > +    gcc_jit_type_get_restrict;
> > > > > > >      gcc_jit_type_get_volatile;
> > > > > >
> > > > > > Please add a new ABI tag (LIBGCCJIT_ABI_25 ?), rather than
> > > > > > adding this
> > > > > > to ABI_0.
> > > > > >
> > > > > > > diff --git a/gcc/testsuite/jit.dg/test-restrict.c
> > > > > > b/gcc/testsuite/jit.dg/test-restrict.c
> > > > > > > new file mode 100644
> > > > > > > index 00000000000..4c8c4407f91
> > > > > > > --- /dev/null
> > > > > > > +++ b/gcc/testsuite/jit.dg/test-restrict.c
> > > > > > > @@ -0,0 +1,77 @@
> > > > > > > +/* { dg-do compile { target x86_64-*-* } } */
> > > > > > > +
> > > > > > > +#include <stdlib.h>
> > > > > > > +#include <stdio.h>
> > > > > > > +
> > > > > > > +#include "libgccjit.h"
> > > > > > > +
> > > > > > > +/* We don't want set_options() in harness.h to set -O3 to
> > > > > > > see that
> > > > > > the cold
> > > > > > > +      attribute affects the optimizations. */
> > > > > >
> > > > > > This refers to a "cold attribute"; is this a vestige of a copy-
> > > > > > and-
> > > > > > paste from a different test case?
> > > > > >
> > > > > > I see that the test scans the generated assembler.  Does the
> > > > > > test
> > > > > > actually verify that restrict has an effect, or was that
> > > > > > another
> > > > > > vestige from a different test case?
> > > > > >
> > > > > > > +#define TEST_ESCHEWS_SET_OPTIONS
> > > > > > > +static void set_options (gcc_jit_context *ctxt, const char
> > > > > > > *argv0)
> > > > > > > +{
> > > > > > > +     // Set "-O3".
> > > > > > > +     gcc_jit_context_set_int_option(ctxt,
> > > > > > GCC_JIT_INT_OPTION_OPTIMIZATION_LEVEL, 3);
> > > > > > > +}
> > > > > > > +
> > > > > > > +#define TEST_COMPILING_TO_FILE
> > > > > > > +#define OUTPUT_KIND      GCC_JIT_OUTPUT_KIND_ASSEMBLER
> > > > > > > +#define OUTPUT_FILENAME  "output-of-test-restrict.c.s"
> > > > > > > +#include "harness.h"
> > > > > > > +
> > > > > > > +void
> > > > > > > +create_code (gcc_jit_context *ctxt, void *user_data)
> > > > > > > +{
> > > > > > > +     /* Let's try to inject the equivalent of:
> > > > > > > +void t(int *__restrict__ a, int *__restrict__ b, char
> > > > > > > *__restrict__
> > > > > > c) {
> > > > > > > +     *a += *c;
> > > > > > > +     *b += *c;
> > > > > > > +}
> > > > > > > +     */
> > > > > > > +     gcc_jit_type *int_type =
> > > > > > > +             gcc_jit_context_get_type (ctxt,
> > > > > > > GCC_JIT_TYPE_INT);
> > > > > > > +     gcc_jit_type *pint_type =
> > > > > > > gcc_jit_type_get_pointer(int_type);
> > > > > > > +     gcc_jit_type *pint_restrict_type =
> > > > > > gcc_jit_type_get_restrict(pint_type);
> > > > > > > +
> > > > > > > +     gcc_jit_type *void_type =
> > > > > > > +             gcc_jit_context_get_type (ctxt,
> > > > > > > GCC_JIT_TYPE_VOID);
> > > > > > > +
> > > > > > > +     gcc_jit_param *a =
> > > > > > > +             gcc_jit_context_new_param (ctxt, NULL,
> > > > > > pint_restrict_type, "a");
> > > > > > > +     gcc_jit_param *b =
> > > > > > > +             gcc_jit_context_new_param (ctxt, NULL,
> > > > > > pint_restrict_type, "b");
> > > > > > > +     gcc_jit_param *c =
> > > > > > > +             gcc_jit_context_new_param (ctxt, NULL,
> > > > > > pint_restrict_type, "c");
> > > > > > > +     gcc_jit_param *params[3] = {a, b, c};
> > > > > > > +
> > > > > > > +     gcc_jit_function *func_t =
> > > > > > > +             gcc_jit_context_new_function (ctxt, NULL,
> > > > > > > +
> > > > > > > GCC_JIT_FUNCTION_EXPORTED,
> > > > > > > +                                     void_type,
> > > > > > > +                                     "t",
> > > > > > > +                                     3, params,
> > > > > > > +                                     0);
> > > > > > > +
> > > > > > > +     gcc_jit_block *block = gcc_jit_function_new_block
> > > > > > > (func_t,
> > > > > > NULL);
> > > > > > > +
> > > > > > > +     /* *a += *c; */
> > > > > > > +     gcc_jit_block_add_assignment_op (
> > > > > > > +             block, NULL,
> > > > > > > +             gcc_jit_rvalue_dereference
> > > > > > > (gcc_jit_param_as_rvalue
> > > > > > (a), NULL),
> > > > > > > +             GCC_JIT_BINARY_OP_PLUS,
> > > > > > > +             gcc_jit_lvalue_as_rvalue (
> > > > > > > +                     gcc_jit_rvalue_dereference
> > > > > > (gcc_jit_param_as_rvalue (c), NULL)));
> > > > > > > +     /* *b += *c; */
> > > > > > > +     gcc_jit_block_add_assignment_op (
> > > > > > > +             block, NULL,
> > > > > > > +             gcc_jit_rvalue_dereference
> > > > > > > (gcc_jit_param_as_rvalue
> > > > > > (b), NULL),
> > > > > > > +             GCC_JIT_BINARY_OP_PLUS,
> > > > > > > +             gcc_jit_lvalue_as_rvalue (
> > > > > > > +                     gcc_jit_rvalue_dereference
> > > > > > (gcc_jit_param_as_rvalue (c), NULL)));
> > > > > > > +
> > > > > > > +     gcc_jit_block_end_with_void_return (block, NULL);
> > > > > > > +}
> > > > > > > +
> > > > > > > +/* { dg-final { jit-verify-output-file-was-created "" } } */
> > > > > > > +/* { dg-final { jit-verify-assembler-output "addl    %eax,
> > > > > > > (%rdi)
> > > > > > > +     addl    %eax, (%rsi)" } } */
> > > > > > > --
> > > > > > > 2.34.1
> > > > > > >
> > > > > >
> > > > > > If this test is meant to run at -O3 and thus can't be part of
> > > > > > test-
> > > > > > combination.c, please add a comment about it to
> > > > > > gcc/testsuite/jit.dg/all-non-failing-tests.h (in the
> > > > > > alphabetical
> > > > > > place).
> > > > > >
> > > > > > The patch also needs to add documentation for the new
> > > > > > entrypoint (in
> > > > > > topics/types.rst), and for the new ABI tag (in
> > > > > > topics/compatibility.rst).
> > > > > >
> > > > > >
> > > > > > Thanks again for the patch; hope the above is constructive
> > > > > > Dave
> > > > > >
> >
>