diff mbox series

[2/6] rtl-ssa: Create REG_UNUSED notes after all pending changes

Message ID 20231024105006.3337671-3-richard.sandiford@arm.com
State New
Headers show
Series rtl-ssa: Various fixes needed for the late-combine pass | expand

Commit Message

Richard Sandiford Oct. 24, 2023, 10:50 a.m. UTC 
Unlike REG_DEAD notes, REG_UNUSED notes need to be kept free of
false positives by all passes.  function_info::change_insns
does this by removing all REG_UNUSED notes, and then using
add_reg_unused_notes to add notes back (or create new ones)
where appropriate.

The problem was that it called add_reg_unused_notes on the fly
while updating each instruction, which meant that the information
for later instructions in the change set wasn't up to date.
This patch does it in a separate loop instead.

gcc/
	* rtl-ssa/changes.cc (function_info::apply_changes_to_insn): Remove
	call to add_reg_unused_notes and instead...
	(function_info::change_insns): ...use a separate loop here.
---
 gcc/rtl-ssa/changes.cc | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Comments

Jeff Law Oct. 24, 2023, 5:22 p.m. UTC | #1 
On 10/24/23 04:50, Richard Sandiford wrote:
> Unlike REG_DEAD notes, REG_UNUSED notes need to be kept free of
> false positives by all passes.  function_info::change_insns
> does this by removing all REG_UNUSED notes, and then using
> add_reg_unused_notes to add notes back (or create new ones)
> where appropriate.
> 
> The problem was that it called add_reg_unused_notes on the fly
> while updating each instruction, which meant that the information
> for later instructions in the change set wasn't up to date.
> This patch does it in a separate loop instead.
> 
> gcc/
> 	* rtl-ssa/changes.cc (function_info::apply_changes_to_insn): Remove
> 	call to add_reg_unused_notes and instead...
> 	(function_info::change_insns): ...use a separate loop here.
OK
jeff
diff mbox series

Patch

diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
index de6222ae736..c73c23c86fb 100644
--- a/gcc/rtl-ssa/changes.cc
+++ b/gcc/rtl-ssa/changes.cc
@@ -586,8 +586,6 @@  function_info::apply_changes_to_insn (insn_change &change)
 
       insn->set_accesses (builder.finish ().begin (), num_defs, num_uses);
     }
-
-  add_reg_unused_notes (insn);
 }
 
 // Add a temporary placeholder instruction after AFTER.
@@ -733,9 +731,14 @@  function_info::change_insns (array_slice<insn_change *> changes)
 	}
     }
 
-  // Finally apply the changes to the underlying insn_infos.
+  // Apply the changes to the underlying insn_infos.
   for (insn_change *change : changes)
     apply_changes_to_insn (*change);
+
+  // Now that the insns and accesses are up to date, add any REG_UNUSED notes.
+  for (insn_change *change : changes)
+    if (!change->is_deletion ())
+      add_reg_unused_notes (change->insn ());
 }
 
 // See the comment above the declaration.