[PR47785] COLLECT_AS_OPTIONS
Kugan Vivekanandarajah
kugan.vivekanandarajah@linaro.org
Fri Nov 8 02:36:00 GMT 2019
Hi Richard,
Thanks for the review.
On Tue, 5 Nov 2019 at 23:08, Richard Biener <richard.guenther@gmail.com> wrote:
>
> On Tue, Nov 5, 2019 at 12:17 AM Kugan Vivekanandarajah
> <kugan.vivekanandarajah@linaro.org> wrote:
> >
> > Hi,
> > Thanks for the review.
> >
> > On Tue, 5 Nov 2019 at 03:57, H.J. Lu <hjl.tools@gmail.com> wrote:
> > >
> > > On Sun, Nov 3, 2019 at 6:45 PM Kugan Vivekanandarajah
> > > <kugan.vivekanandarajah@linaro.org> wrote:
> > > >
> > > > Thanks for the reviews.
> > > >
> > > >
> > > > On Sat, 2 Nov 2019 at 02:49, H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > >
> > > > > On Thu, Oct 31, 2019 at 6:33 PM Kugan Vivekanandarajah
> > > > > <kugan.vivekanandarajah@linaro.org> wrote:
> > > > > >
> > > > > > On Wed, 30 Oct 2019 at 03:11, H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > > >
> > > > > > > On Sun, Oct 27, 2019 at 6:33 PM Kugan Vivekanandarajah
> > > > > > > <kugan.vivekanandarajah@linaro.org> wrote:
> > > > > > > >
> > > > > > > > Hi Richard,
> > > > > > > >
> > > > > > > > Thanks for the review.
> > > > > > > >
> > > > > > > > On Wed, 23 Oct 2019 at 23:07, Richard Biener <richard.guenther@gmail.com> wrote:
> > > > > > > > >
> > > > > > > > > On Mon, Oct 21, 2019 at 10:04 AM Kugan Vivekanandarajah
> > > > > > > > > <kugan.vivekanandarajah@linaro.org> wrote:
> > > > > > > > > >
> > > > > > > > > > Hi Richard,
> > > > > > > > > >
> > > > > > > > > > Thanks for the pointers.
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > On Fri, 11 Oct 2019 at 22:33, Richard Biener <richard.guenther@gmail.com> wrote:
> > > > > > > > > > >
> > > > > > > > > > > On Fri, Oct 11, 2019 at 6:15 AM Kugan Vivekanandarajah
> > > > > > > > > > > <kugan.vivekanandarajah@linaro.org> wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > Hi Richard,
> > > > > > > > > > > > Thanks for the review.
> > > > > > > > > > > >
> > > > > > > > > > > > On Wed, 2 Oct 2019 at 20:41, Richard Biener <richard.guenther@gmail.com> wrote:
> > > > > > > > > > > > >
> > > > > > > > > > > > > On Wed, Oct 2, 2019 at 10:39 AM Kugan Vivekanandarajah
> > > > > > > > > > > > > <kugan.vivekanandarajah@linaro.org> wrote:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Hi,
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > As mentioned in the PR, attached patch adds COLLECT_AS_OPTIONS for
> > > > > > > > > > > > > > passing assembler options specified with -Wa, to the link-time driver.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > The proposed solution only works for uniform -Wa options across all
> > > > > > > > > > > > > > TUs. As mentioned by Richard Biener, supporting non-uniform -Wa flags
> > > > > > > > > > > > > > would require either adjusting partitioning according to flags or
> > > > > > > > > > > > > > emitting multiple object files from a single LTRANS CU. We could
> > > > > > > > > > > > > > consider this as a follow up.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Bootstrapped and regression tests on arm-linux-gcc. Is this OK for trunk?
> > > > > > > > > > > > >
> > > > > > > > > > > > > While it works for your simple cases it is unlikely to work in practice since
> > > > > > > > > > > > > your implementation needs the assembler options be present at the link
> > > > > > > > > > > > > command line. I agree that this might be the way for people to go when
> > > > > > > > > > > > > they face the issue but then it needs to be documented somewhere
> > > > > > > > > > > > > in the manual.
> > > > > > > > > > > > >
> > > > > > > > > > > > > That is, with COLLECT_AS_OPTION (why singular? I'd expected
> > > > > > > > > > > > > COLLECT_AS_OPTIONS) available to cc1 we could stream this string
> > > > > > > > > > > > > to lto_options and re-materialize it at link time (and diagnose mismatches
> > > > > > > > > > > > > even if we like).
> > > > > > > > > > > > OK. I will try to implement this. So the idea is if we provide
> > > > > > > > > > > > -Wa,options as part of the lto compile, this should be available
> > > > > > > > > > > > during link time. Like in:
> > > > > > > > > > > >
> > > > > > > > > > > > arm-linux-gnueabihf-gcc -march=armv7-a -mthumb -O2 -flto
> > > > > > > > > > > > -Wa,-mimplicit-it=always,-mthumb -c test.c
> > > > > > > > > > > > arm-linux-gnueabihf-gcc -flto test.o
> > > > > > > > > > > >
> > > > > > > > > > > > I am not sure where should we stream this. Currently, cl_optimization
> > > > > > > > > > > > has all the optimization flag provided for compiler and it is
> > > > > > > > > > > > autogenerated and all the flags are integer values. Do you have any
> > > > > > > > > > > > preference or example where this should be done.
> > > > > > > > > > >
> > > > > > > > > > > In lto_write_options, I'd simply append the contents of COLLECT_AS_OPTIONS
> > > > > > > > > > > (with -Wa, prepended to each of them), then recover them in lto-wrapper
> > > > > > > > > > > for each TU and pass them down to the LTRANS compiles (if they agree
> > > > > > > > > > > for all TUs, otherwise I'd warn and drop them).
> > > > > > > > > >
> > > > > > > > > > Attached patch streams it and also make sure that the options are the
> > > > > > > > > > same for all the TUs. Maybe it is a bit restrictive.
> > > > > > > > > >
> > > > > > > > > > What is the best place to document COLLECT_AS_OPTIONS. We don't seem
> > > > > > > > > > to document COLLECT_GCC_OPTIONS anywhere ?
> > > > > > > > >
> > > > > > > > > Nowhere, it's an implementation detail then.
> > > > > > > > >
> > > > > > > > > > Attached patch passes regression and also fixes the original ARM
> > > > > > > > > > kernel build issue with tumb2.
> > > > > > > > >
> > > > > > > > > Did you try this with multiple assembler options? I see you stream
> > > > > > > > > them as -Wa,-mfpu=xyz,-mthumb but then compare the whole
> > > > > > > > > option strings so a mismatch with -Wa,-mthumb,-mfpu=xyz would be
> > > > > > > > > diagnosed. If there's a spec induced -Wa option do we get to see
> > > > > > > > > that as well? I can imagine -march=xyz enabling a -Wa option
> > > > > > > > > for example.
> > > > > > > > >
> > > > > > > > > + *collect_as = XNEWVEC (char, strlen (args_text) + 1);
> > > > > > > > > + strcpy (*collect_as, args_text);
> > > > > > > > >
> > > > > > > > > there's strdup. Btw, I'm not sure why you don't simply leave
> > > > > > > > > the -Wa option in the merged options [individually] and match
> > > > > > > > > them up but go the route of comparing strings and carrying that
> > > > > > > > > along separately. I think that would be much better.
> > > > > > > >
> > > > > > > > Is attached patch which does this is OK?
> > > > > > > >
> > > > > > >
> > > > > > > Don't you need to also handle -Xassembler? Since -Wa, doesn't work with comma in
> > > > > > > assembler options, like -mfoo=foo1,foo2, one needs to use
> > > > > > >
> > > > > > > -Xassembler -mfoo=foo1,foo2
> > > > > > >
> > > > > > > to pass -mfoo=foo1,foo2 to assembler.
> > > > > >
> > > > > >
> > > > > > gcc -flto -O2 -Wa,-mcpu=zzz1 -mcpu=xxx1 -c foo.c
> > > > > > gcc -flto -O2 -Wa,-mcpu=zzz2 -mcpu=xxx2 -c bar.c
> > > > > >
> > > > > > What should be the option we should provide for the final
> > > > > > gcc -flto foo.o bar.o -o out
> > > > > >
> > > > > > I think our ultimate aim is to handle this in LTO partitioning. That
> > > > > > is, we should create partitioning such that each partition has the
> > > > > > same -Wa options. This could also handle -Xassembler -mfoo=foo1,foo2
> > > > > > which H.J. Lu wanted. We need to modify the heuristics and do some
> > > > > > performance testing.
> > > > > >
> > > > > > In the meantime we could push a simpler solution which is to accept
> > > > > > -Wa option if they are identical. This would fix at least some of the
> > > > > > reported cases. Trying to work out what is compatible options, even if
> > > > > > we ask the back-end to do this, is not a straightforward strategy and
> > > > > > can be a maintenance nightmare. Unless we can query GNU AS somehow. If
> > > > > > I am missing something please let me know.
> > > > >
> > > > > +/* Store switches specified for as with -Wa in COLLECT_AS_OPTIONS
> > > > > + and place that in the environment. */
> > > > > +static void
> > > > > +putenv_COLLECT_AS_OPTIONS (vec<char_p> vec)
> > > > > +{
> > > > > + unsigned ix;
> > > > > + char *opt;
> > > > > + int len = vec.length ();
> > > > > +
> > > > > + if (!len)
> > > > > + return;
> > > > > +
> > > > > + obstack_init (&collect_obstack);
> > > > > + obstack_grow (&collect_obstack, "COLLECT_AS_OPTIONS=",
> > > > > + sizeof ("COLLECT_AS_OPTIONS=") - 1);
> > > > > + obstack_grow (&collect_obstack, "-Wa,", strlen ("-Wa,"));
> > > > > +
> > > > > + FOR_EACH_VEC_ELT (vec, ix, opt)
> > > > > + {
> > > > > + obstack_grow (&collect_obstack, opt, strlen (opt));
> > > > > + --len;
> > > > > + if (len)
> > > > > + obstack_grow (&collect_obstack, ",", strlen (","));
> > > > > + }
> > > > > +
> > > > > + xputenv (XOBFINISH (&collect_obstack, char *));
> > > > >
> > > > > This missed the null terminator.
> > > >
> > > > Attached patch addresses the review comments I got so far.
> > > >
> > >
> > > + if (len)
> > > + obstack_grow (&collect_obstack, ",", strlen (","));
> > >
> > > Why not sizeof (",") - 1?
> > I guess I copied and pasted it from elsewhere else. We seem to use
> > both. I have changed it now.
> >
> > >
> > > diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c
> > > index 9a7bbd0c022..148c52906d1 100644
> > > --- a/gcc/lto-wrapper.c
> > > +++ b/gcc/lto-wrapper.c
> > > @@ -253,6 +253,11 @@ merge_and_complain (struct cl_decoded_option
> > > **decoded_options,
> > > break;
> > >
> > > default:
> > > + if (foption->opt_index == OPT_Wa_)
> > > + {
> > > + append_option (decoded_options, decoded_options_count, foption);
> > > + break;
> > > + }
> > > if (!(cl_options[foption->opt_index].flags & CL_TARGET))
> > > break;
> > >
> > > Why not use "case OPT_Wa_:" here?
> > Done.
> > >
> > > For
> > >
> > > + static const char *collect_as;
> > > + for (unsigned int j = 1; j < count; ++j)
> > > + {
> > > + struct cl_decoded_option *option = &opts[j];
> > > + if (j == 1)
> > > + collect_as = NULL;
> > >
> > > why not simply
> > >
> > > const char *collect_as = NULL?
> >
> > I wanted to make sure that if we call this from multiple places, it
> > still works. I guess it is still going to be the same. I have changed
> > it now as you have suggested.
> >
> > Is this revised patch OK? I will do a fresh bootstrap and regression
> > testing before committing.
>
> In putenv_COLLECT_AS_OPTIONS you'll happily make
> -Wa,-march=foo,bar out of -Xassembler -march=foo,bar which
> will later cause us to fail to assemble with unknown assembler options.
> May I suggest to instead always use -Xassembler syntax in
> COLLECT_AS_OPTIONS? Please also make sure to quote
> options the same way set_collect_gcc_options does
> (with '', separated by spaces). Then the lto-opts.c part
> becomes "easier" as you can simply copy the string to the
> obstack without wrapping it again with append_to_collect_gcc_options.
>
> In lto-wrapper you then only have to handle OPT_Xassembler.
I changes it to look:
static void
putenv_COLLECT_AS_OPTIONS (vec<char_p> vec)
{
unsigned ix;
char *opt;
int len = vec.length ();
if (!len)
return;
obstack_init (&collect_obstack);
obstack_grow (&collect_obstack, "COLLECT_AS_OPTIONS=",
sizeof ("COLLECT_AS_OPTIONS=") - 1);
FOR_EACH_VEC_ELT (vec, ix, opt)
{
obstack_grow (&collect_obstack, "-Xassembler ",
sizeof ("-Xassembler ") - 1);
obstack_grow (&collect_obstack, opt, strlen (opt));
}
obstack_1grow (&collect_obstack, '\0');
xputenv (XOBFINISH (&collect_obstack, char *));
}
But when I use it,
gcc -flto f.c -Wa,-mimplicit-it=always -c
or gcc -flto f.c -Xassembler -mimplicit-it=always -c
gcc -flto l.o f.o
foptions->original_option_with_args_text "-Xassembler
-mimplicit-it=always" is decoded as 1493 (OPT_SPECIAL_unknown) Am I
missing something here (from decode_cmdline_options_to_array). I
expected it to be OPT_Xassembler
>
> You simply end up appending _all_ assembler options in order
> of TUs processed by lto-wrapper to the final command (N times
> even if exactly the same). I'm also not sure how you can check
> for positional equivalence (or if we even should). With -Wa
> we could compare the full option string but with separate -Xassembler
> we're having a more difficult task here. OTOH your patch doesn't
> do any comparing here.
in
+
+static void
+append_compiler_wa_options (obstack *argv_obstack,
+ struct cl_decoded_option *opts,
+ unsigned int count)
+{
+ static const char *collect_as = NULL;
+ for (unsigned int j = 1; j < count; ++j)
+ {
+ struct cl_decoded_option *option = &opts[j];
+ if (option->opt_index != OPT_Wa_)
+ continue;
+ const char *args_text = option->orig_option_with_args_text;
+ /* We expect all the -Wa, options to be same. */
+ if (collect_as && strcmp (collect_as, args_text) != 0)
+ fatal_error (input_location, "-Wa, options does not match");
+ if (!collect_as)
+ {
+ obstack_ptr_grow (argv_obstack, args_text);
+ collect_as = args_text;
+ }
+ }
+}
I am only copying once. Also accept if all the arguments are same or
empty. Am I missing something here.
>
> Your append_compiler_wa_options should be merged into
> append_compiler_options, passing -Xassembler through.
OK.
>
> Thanks,
> Richard.
>
> > Thanks,
> > Kugan
> >
> > >
> > >
> > > H.J.
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