aarch64: Re-parent trailing nondebug base reg uses [PR113089]

While working on PR113089, I realised we where missing code to re-parent
trailing nondebug uses of the base register in the case of cancelling
writeback in the load/store pair pass.  This patch fixes that.

gcc/ChangeLog:

	PR target/113089
	* config/aarch64/aarch64-ldp-fusion.cc (ldp_bb_info::fuse_pair):
	Update trailing nondebug uses of the base register in the case
	of cancelling writeback.

diff --git a/gcc/config/aarch64/aarch64-ldp-fusion.cc b/gcc/config/aarch64/aarch64-ldp-fusion.cc
index bbb95d6c820a99c8103284ab6a7dcc5b0e0c88f9..e3827e980107de8706f52db7456b2928c11ac32d 100644 (file)
--- a/gcc/config/aarch64/aarch64-ldp-fusion.cc
+++ b/gcc/config/aarch64/aarch64-ldp-fusion.cc
@@ -1693,6 +1693,30 @@ ldp_bb_info::fuse_pair (bool load_p,
 
   if (trailing_add)
     changes.safe_push (make_delete (trailing_add));
+  else if ((writeback & 2) && !writeback_effect)
+    {
+      // The second insn initially had writeback but now the pair does not,
+      // need to update any nondebug uses of the base register def in the
+      // second insn.  We'll take care of debug uses later.
+      auto def = find_access (insns[1]->defs (), base_regno);
+      gcc_assert (def);
+      auto set = dyn_cast<set_info *> (def);
+      if (set && set->has_nondebug_uses ())
+       {
+         auto orig_use = find_access (insns[0]->uses (), base_regno);
+         for (auto use : set->nondebug_insn_uses ())
+           {
+             auto change = make_change (use->insn ());
+             change->new_uses = check_remove_regno_access (attempt,
+                                                           change->new_uses,
+                                                           base_regno);
+             change->new_uses = insert_access (attempt,
+                                               orig_use,
+                                               change->new_uses);
+             changes.safe_push (change);
+           }
+       }
+    }
 
   auto is_changing = insn_is_changing (changes);
   for (unsigned i = 0; i < changes.length (); i++)