On 22/01/2024 13:49, Richard Sandiford wrote:
> Alex Coplan <alex.cop...@arm.com> writes:
> > In r14-5820-ga49befbd2c783e751dc2110b544fe540eb7e33eb I added support to
> > RTL-SSA for inserting new insns, which included support for users
> > creating new defs.
> >
> > However, I missed that apply_changes_to_insn needed updating to ensure
> > that the new defs actually got inserted into the main def chain. This
> > meant that when the aarch64 ldp/stp pass inserted a new stp insn, the
> > stp would just get skipped over during subsequent alias analysis, as its
> > def never got inserted into the memory def chain. This (unsurprisingly)
> > led to wrong code.
> >
> > This patch fixes the issue by ensuring new user-created defs get
> > inserted. I would have preferred to have used a flag internal to the
> > defs instead of a separate data structure to keep track of them, but since
> > machine_mode increased to 16 bits we're already at 64 bits in access_info,
> > and we can't really reuse m_is_temp as the logic in finalize_new_accesses
> > requires it to get cleared.
> >
> > Bootstrapped/regtested as a series on aarch64-linux-gnu, OK for trunk?
> >
> > Thanks,
> > Alex
> >
> > gcc/ChangeLog:
> >
> > PR target/113070
> > * rtl-ssa.h: Include hash-set.h.
> > * rtl-ssa/changes.cc (function_info::finalize_new_accesses): Add
> > new_sets parameter and use it to keep track of new user-created sets.
> > (function_info::apply_changes_to_insn): Also call add_def on new sets.
> > (function_info::change_insns): Add hash_set to keep track of new
> > user-created defs. Plumb it through.
> > * rtl-ssa/functions.h: Add hash_set parameter to finalize_new_accesses
> > and
> > apply_changes_to_insn.
> > ---
> > gcc/rtl-ssa.h | 1 +
> > gcc/rtl-ssa/changes.cc | 28 +++++++++++++++++++++-------
> > gcc/rtl-ssa/functions.h | 6 ++++--
> > 3 files changed, 26 insertions(+), 9 deletions(-)
> >
> > diff --git a/gcc/rtl-ssa.h b/gcc/rtl-ssa.h
> > index f0cf656f5ac..17337639ae8 100644
> > --- a/gcc/rtl-ssa.h
> > +++ b/gcc/rtl-ssa.h
> > @@ -50,6 +50,7 @@
> > #include "mux-utils.h"
> > #include "rtlanal.h"
> > #include "cfgbuild.h"
> > +#include "hash-set.h"
> >
> > // Provides the global crtl->ssa.
> > #include "memmodel.h"
> > diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
> > index ce51d6ccd8d..6119ec3535b 100644
> > --- a/gcc/rtl-ssa/changes.cc
> > +++ b/gcc/rtl-ssa/changes.cc
> > @@ -429,7 +429,8 @@ update_insn_in_place (insn_change &change)
> > // POS gives the final position of INSN, which hasn't yet been moved into
> > // place.
>
> The new parameter should be documented. How about:
>
> // place. NEW_SETS contains the new set_infos that are being added as part
> // of this change (as opposed to being moved or repurposed from existing
> // instructions).
That comment looks appropriate for apply_changes_to_insn, where NEW_SETS has
already been populated, but doesn't seem accurate for finalize_new_accesses.
How about:
// place. Keep track of any newly-created set_infos being added as
// part of this change by adding them to NEW_SETS.
for finalize_new_accesses? OK with that change (and using your suggestion for
apply_changes_to_insn)?
Thanks,
Alex
>
>
> > void
> > -function_info::finalize_new_accesses (insn_change &change, insn_info *pos)
> > +function_info::finalize_new_accesses (insn_change &change, insn_info *pos,
> > + hash_set<def_info *> &new_sets)
> > {
> > insn_info *insn = change.insn ();
> >
> > @@ -465,6 +466,12 @@ function_info::finalize_new_accesses (insn_change
> > &change, insn_info *pos)
> > // later in case we see a second write to the same resource.
> > def_info *perm_def = allocate<set_info> (change.insn (),
> > def->resource ());
> > +
> > + // Keep track of the new set so we remember to add it to the
> > + // def chain later.
> > + if (new_sets.add (perm_def))
> > + gcc_unreachable (); // We shouldn't see duplicates here.
> > +
> > def->set_last_def (perm_def);
> > def = perm_def;
> > }
> > @@ -647,7 +654,8 @@ function_info::finalize_new_accesses (insn_change
> > &change, insn_info *pos)
> > // Copy information from CHANGE to its underlying insn_info, given that
> > // the insn_info has already been placed appropriately.
>
> Similarly here.
>
> OK with those changes, thanks.
>
> Richard
>
> > void
> > -function_info::apply_changes_to_insn (insn_change &change)
> > +function_info::apply_changes_to_insn (insn_change &change,
> > + hash_set<def_info *> &new_sets)
> > {
> > insn_info *insn = change.insn ();
> > if (change.is_deletion ())
> > @@ -659,10 +667,11 @@ function_info::apply_changes_to_insn (insn_change
> > &change)
> > // Copy the cost.
> > insn->set_cost (change.new_cost);
> >
> > - // Add all clobbers. Sets and call clobbers never move relative to
> > - // other definitions, so are OK as-is.
> > + // Add all clobbers and newly-created sets. Existing sets and call
> > + // clobbers never move relative to other definitions, so are OK as-is.
> > for (def_info *def : change.new_defs)
> > - if (is_a<clobber_info *> (def) && !def->is_call_clobber ())
> > + if ((is_a<clobber_info *> (def) && !def->is_call_clobber ())
> > + || (is_a<set_info *> (def) && new_sets.contains (def)))
> > add_def (def);
> >
> > // Add all uses, now that their position is final.
> > @@ -793,6 +802,10 @@ function_info::change_insns (array_slice<insn_change
> > *> changes)
> > placeholders[i] = placeholder;
> > }
> >
> > + // We need to keep track of newly-added sets as these need adding to
> > + // the def chain later.
> > + hash_set<def_info *> new_sets;
> > +
> > // Finalize the new list of accesses for each change. Don't install
> > them yet,
> > // so that we still have access to the old lists below.
> > //
> > @@ -806,7 +819,8 @@ function_info::change_insns (array_slice<insn_change *>
> > changes)
> > insn_info *placeholder = placeholders[i];
> > if (!change.is_deletion ())
> > finalize_new_accesses (change,
> > - placeholder ? placeholder : change.insn ());
> > + placeholder ? placeholder : change.insn (),
> > + new_sets);
> > }
> >
> > // Remove all definitions that are no longer needed. After the above,
> > @@ -861,7 +875,7 @@ function_info::change_insns (array_slice<insn_change *>
> > changes)
> >
> > // Apply the changes to the underlying insn_infos.
> > for (insn_change *change : changes)
> > - apply_changes_to_insn (*change);
> > + apply_changes_to_insn (*change, new_sets);
> >
> > // Now that the insns and accesses are up to date, add any REG_UNUSED
> > notes.
> > for (insn_change *change : changes)
> > diff --git a/gcc/rtl-ssa/functions.h b/gcc/rtl-ssa/functions.h
> > index 962180e27d6..4573453d896 100644
> > --- a/gcc/rtl-ssa/functions.h
> > +++ b/gcc/rtl-ssa/functions.h
> > @@ -299,8 +299,10 @@ private:
> > void process_uses_of_deleted_def (set_info *);
> > insn_info *add_placeholder_after (insn_info *);
> > void possibly_queue_changes (insn_change &);
> > - void finalize_new_accesses (insn_change &, insn_info *);
> > - void apply_changes_to_insn (insn_change &);
> > + void finalize_new_accesses (insn_change &, insn_info *,
> > + hash_set<def_info *> &);
> > + void apply_changes_to_insn (insn_change &,
> > + hash_set<def_info *> &);
> >
> > void init_function_data ();
> > void calculate_potential_phi_regs (build_info &);
