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rtl-ssa: Run finalize_new_accesses forwards [PR113070]

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The next patch in this series exposes an interface for creating new uses
in RTL-SSA.  The intent is that new user-created uses can consume new
user-created defs in the same change group.  This is so that we can
correctly update uses of memory when inserting a new store pair insn in
the aarch64 load/store pair fusion pass (the affected uses need to
consume the new store pair insn).

As it stands, finalize_new_accesses is called as part of the backwards
insn placement loop within change_insns, but if we want new uses to be
able to depend on new defs in the same change group, we need
finalize_new_accesses to be called on earlier insns first.  This is so
that when we process temporary uses and turn them into permanent uses,
we can follow the last_def link on the temporary def to ensure we end up
with a permanent use consuming a permanent def.

gcc/ChangeLog:

	PR target/113070
	* rtl-ssa/changes.cc (function_info::change_insns): Split out the call
	to finalize_new_accesses from the backwards placement loop, run it
	forwards in a separate loop.
This commit is contained in:
Alex Coplan 2024-01-11 16:17:37 +00:00
parent d5d43dc399
commit e0374b028a
1 changed files with 16 additions and 5 deletions
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21
gcc/rtl-ssa/changes.cc
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@ -775,15 +775,26 @@ function_info::change_insns (array_slice<insn_change *> changes)
placeholder = add_placeholder_after (after);
following_insn = placeholder;
}
// Finalize the new list of accesses for the change. Don't install
// them yet, so that we still have access to the old lists below.
finalize_new_accesses (change,
placeholder ? placeholder : insn);
}
placeholders[i] = placeholder;
}
// 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.
//
// Note that we do this forwards instead of in the backwards loop above so
// that any new defs being inserted are processed before new uses of those
// defs, so that the (initially) temporary uses referring to temporary defs
// can be easily updated to become permanent uses referring to permanent defs.
for (unsigned i = 0; i < changes.size (); i++)
{
insn_change &change = *changes[i];
insn_info *placeholder = placeholders[i];
if (!change.is_deletion ())
finalize_new_accesses (change,
placeholder ? placeholder : change.insn ());
}
// Remove all definitions that are no longer needed. After the above,
// the only uses of such definitions should be dead phis and now-redundant
// live-out uses.