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* [gcc(refs/vendors/riscv/heads/gcc-13-with-riscv-opts)] mode-switching: Avoid quadractic list operation
@ 2023-11-21 4:11 Jeff Law
0 siblings, 0 replies; only message in thread
From: Jeff Law @ 2023-11-21 4:11 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:05de0ef2e53ad1ad82feac0954aa61626304317f
commit 05de0ef2e53ad1ad82feac0954aa61626304317f
Author: Richard Sandiford <richard.sandiford@arm.com>
Date: Sat Nov 11 17:28:55 2023 +0000
mode-switching: Avoid quadractic list operation
add_seginfo chained insn information to the end of a list
by starting at the head of the list. This patch avoids the
quadraticness by keeping track of the tail pointer.
gcc/
* mode-switching.cc (add_seginfo): Replace head pointer with
a pointer to the tail pointer.
(optimize_mode_switching): Update calls accordingly.
(cherry picked from commit 174ee5115a3004d3664165e9d619535b579111d4)
Diff:
---
gcc/mode-switching.cc | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)
diff --git a/gcc/mode-switching.cc b/gcc/mode-switching.cc
index 8577069bde1..bebe89d5fd2 100644
--- a/gcc/mode-switching.cc
+++ b/gcc/mode-switching.cc
@@ -162,23 +162,14 @@ new_seginfo (int mode, rtx_insn *insn, const HARD_REG_SET ®s_live)
}
/* Add a seginfo element to the end of a list.
- HEAD is a pointer to the list beginning.
+ TAIL is a pointer to the list's null terminator.
INFO is the structure to be linked in. */
static void
-add_seginfo (struct bb_info *head, struct seginfo *info)
+add_seginfo (struct seginfo ***tail_ptr, struct seginfo *info)
{
- struct seginfo *ptr;
-
- if (head->seginfo == NULL)
- head->seginfo = info;
- else
- {
- ptr = head->seginfo;
- while (ptr->next != NULL)
- ptr = ptr->next;
- ptr->next = info;
- }
+ **tail_ptr = info;
+ *tail_ptr = &info->next;
}
/* Record in LIVE that register REG died. */
@@ -574,6 +565,7 @@ optimize_mode_switching (void)
Also compute the initial transparency settings. */
FOR_EACH_BB_FN (bb, cfun)
{
+ struct seginfo **tail_ptr = &info[bb->index].seginfo;
struct seginfo *ptr;
int last_mode = no_mode;
bool any_set_required = false;
@@ -599,7 +591,7 @@ optimize_mode_switching (void)
if (ins_pos != BB_END (bb))
ins_pos = NEXT_INSN (ins_pos);
ptr = new_seginfo (no_mode, ins_pos, live_now);
- add_seginfo (info + bb->index, ptr);
+ add_seginfo (&tail_ptr, ptr);
for (i = 0; i < no_mode; i++)
clear_mode_bit (transp[bb->index], j, i);
}
@@ -617,7 +609,7 @@ optimize_mode_switching (void)
any_set_required = true;
last_mode = mode;
ptr = new_seginfo (mode, insn, live_now);
- add_seginfo (info + bb->index, ptr);
+ add_seginfo (&tail_ptr, ptr);
for (i = 0; i < no_mode; i++)
clear_mode_bit (transp[bb->index], j, i);
}
@@ -646,7 +638,7 @@ optimize_mode_switching (void)
if (!any_set_required)
{
ptr = new_seginfo (no_mode, BB_END (bb), live_now);
- add_seginfo (info + bb->index, ptr);
+ add_seginfo (&tail_ptr, ptr);
if (last_mode != no_mode)
for (i = 0; i < no_mode; i++)
clear_mode_bit (transp[bb->index], j, i);
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