On Sun, Nov 3, 2019 at 6:45 PM Kugan Vivekanandarajah
<kugan.vivekanandara...@linaro.org> wrote:
>
> Thanks for the reviews.
>
>
> On Sat, 2 Nov 2019 at 02:49, H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > On Thu, Oct 31, 2019 at 6:33 PM Kugan Vivekanandarajah
> > <kugan.vivekanandara...@linaro.org> wrote:
> > >
> > > On Wed, 30 Oct 2019 at 03:11, H.J. Lu <hjl.to...@gmail.com> wrote:
> > > >
> > > > On Sun, Oct 27, 2019 at 6:33 PM Kugan Vivekanandarajah
> > > > <kugan.vivekanandara...@linaro.org> wrote:
> > > > >
> > > > > Hi Richard,
> > > > >
> > > > > Thanks for the review.
> > > > >
> > > > > On Wed, 23 Oct 2019 at 23:07, Richard Biener
> > > > > <richard.guent...@gmail.com> wrote:
> > > > > >
> > > > > > On Mon, Oct 21, 2019 at 10:04 AM Kugan Vivekanandarajah
> > > > > > <kugan.vivekanandara...@linaro.org> wrote:
> > > > > > >
> > > > > > > Hi Richard,
> > > > > > >
> > > > > > > Thanks for the pointers.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > On Fri, 11 Oct 2019 at 22:33, Richard Biener
> > > > > > > <richard.guent...@gmail.com> wrote:
> > > > > > > >
> > > > > > > > On Fri, Oct 11, 2019 at 6:15 AM Kugan Vivekanandarajah
> > > > > > > > <kugan.vivekanandara...@linaro.org> wrote:
> > > > > > > > >
> > > > > > > > > Hi Richard,
> > > > > > > > > Thanks for the review.
> > > > > > > > >
> > > > > > > > > On Wed, 2 Oct 2019 at 20:41, Richard Biener
> > > > > > > > > <richard.guent...@gmail.com> wrote:
> > > > > > > > > >
> > > > > > > > > > On Wed, Oct 2, 2019 at 10:39 AM Kugan Vivekanandarajah
> > > > > > > > > > <kugan.vivekanandara...@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?
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?
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?
H.J.
