From 49bfda6017e105df46fa8d12d7f067da423a1d3c Mon Sep 17 00:00:00 2001
From: Alex Coplan <alex.coplan@arm.com>
Date: Mon, 15 Jan 2024 17:13:06 +0000
Subject: [PATCH] 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.
---
gcc/config/aarch64/aarch64-ldp-fusion.cc | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/gcc/config/aarch64/aarch64-ldp-fusion.cc b/gcc/config/aarch64/aarch64-ldp-fusion.cc
index bbb95d6c820a..e3827e980107 100644
--- 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++)
--
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