Re: [gofrontend-dev] Re: Go patch committed: Intrinsify runtime/internal/atomic functions

["Cherry Zhang via gcc-patches" <gcc-patches at gcc dot gnu dot org>]

Jim, thank you for the fix! The patch looks good to me. Maybe we should
also apply this to __atomic_add_fetch_4 and __atomic_add_fetch_8?

Thanks,
Cherry



On Tue, May 21, 2019 at 11:25 PM Jim Wilson <jimw@sifive.com> wrote:

> On Sun, May 19, 2019 at 5:22 AM Andreas Schwab <schwab@linux-m68k.org>
> wrote:
> > ../../../libgo/go/runtime/mbitmap.go: In function
> ‘runtime.setMarked.runtime.markBits’:
> > ../../../libgo/go/runtime/mbitmap.go:291:9: internal compiler error:
> Segmentation fault
> >   291 |  atomic.Or8(m.bytep, m.mask)
> >       |         ^
>
> This is failing for RISC-V because __atomic_or_fetch_1 isn't a
> built-in function that can be expanded inline.  You have to call the
> library function in libatomic.  The C front-end is registering all of
> the built-in functions, but it looks like the go front-end is only
> registering functions it thinks it needs and this list is incomplete.
> In expand_builtin, case BUILT_IN_ATOMIC_OR_FETCH_1, the external
> library call for this gets set to BUILT_IN_ATOMIC_FETCH_OR_1.  Then in
> expand_builtin_atomic_fetch_op when we call builtin_decl_explicit
> (ext_call) it returns NULL.  This is because the go front end
> registered BUILT_IN_ATOMIC_OR_FETCH_1 as a built-in, but did not
> register BUILT_IN_ATOMIC_FETCH_OR_1 as a built-in.  The NULL return
> from builtin_decl_explicit gives us an ADDR_EXPR with a NULL operand
> which eventually causes the internal compiler error.  It looks like
> the same thing is done with all of the op_fetch built-ins, so use of
> any of them means that the fetch_op built-in also has to be
> registered.  I verified with a quick hack that I need both
> BUILT_IN_ATOMIC_FETCH_OR_1 and BUILT_IN_ATOMIC_FETCH_AND_1 defined as
> built-ins to make a RISC-V go build work.  I haven't done any testing
> yet.
>
> Jim
>
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