From: Jin Ma <jinma@linux.alibaba.com>
To: gcc-patches@gcc.gnu.org
Cc: jeffreyalaw@gmail.com, richard.sandiford@arm.com,
kito.cheng@gmail.com, christoph.muellner@vrull.eu,
jinma.contrib@gmail.com, Jin Ma <jinma@linux.alibaba.com>
Subject: [PATCH] In the pipeline, UNRECOG INSN is not executed in advance if it starts a live range.
Date: Mon, 29 May 2023 18:51:20 +0800 [thread overview]
Message-ID: <20230529105120.1703-1-jinma@linux.alibaba.com> (raw)
In-Reply-To: <b86699b5-3eae-ff52-3e52-f54bbd6f5a40@gmail.com>
Unrecog insns (such as CLOBBER, USE) does not represent real instructions, but in the
process of pipeline optimization, they will wait for transmission in ready list like
other insns, without considering resource conflicts and cycles. This results in a
multi-issue CPU architecture that can be issued at any time if other regular insns
have resource conflicts or cannot be launched for other reasons. As a result, its
position is advanced in the generated insns sequence, which will affect register
allocation and often lead to more redundant mov instructions.
A simple example:
https://github.com/majin2020/gcc-test/blob/master/test.c
This is a function in the dhrystone benchmark.
https://github.com/majin2020/gcc-test/blob/0b08c1a13de9663d7d9aba7539b960ec0607ca24/test.c.299r.sched1
This is a log of the pass 'sched1' When issue_rate == 2. Among them, insn 13 and 14 are
much ahead of schedule, which risks generating redundant mov instructions, which seems
unreasonable.
Therefore, I submit patch again on the basis of the last review opinions to try to solve
this problem.
This is the new log of shed1 after patch is added.
https://github.com/majin2020/gcc-test/commit/efcb43e3369e771bde702955048bfe3f501263dd
gcc/ChangeLog:
* haifa-sched.cc (unrecog_insn_for_forw_only_p): New.
(prune_ready_list): UNRECOG INSN is not executed in advance if it starts a
live range.
---
gcc/haifa-sched.cc | 44 +++++++++++++++++++++++++++++++++++++++-----
1 file changed, 39 insertions(+), 5 deletions(-)
diff --git a/gcc/haifa-sched.cc b/gcc/haifa-sched.cc
index 2c881ede0ec..205680a4936 100644
--- a/gcc/haifa-sched.cc
+++ b/gcc/haifa-sched.cc
@@ -765,6 +765,23 @@ real_insn_for_shadow (rtx_insn *insn)
return pair->i1;
}
+/* Return true if INSN is unrecog that starts a live range. */
+
+static bool
+unrecog_insn_for_forw_only_p (rtx_insn *insn)
+{
+ if (insn && !INSN_P (insn) && recog_memoized (insn) >= 0)
+ return false;
+
+ if ((GET_CODE (PATTERN (insn)) == CLOBBER
+ || GET_CODE (PATTERN (insn)) == USE)
+ && !sd_lists_empty_p (insn, SD_LIST_FORW)
+ && sd_lists_empty_p (insn, SD_LIST_BACK))
+ return true;
+
+ return false;
+}
+
/* For a pair P of insns, return the fixed distance in cycles from the first
insn after which the second must be scheduled. */
static int
@@ -6320,11 +6337,28 @@ prune_ready_list (state_t temp_state, bool first_cycle_insn_p,
}
else if (recog_memoized (insn) < 0)
{
- if (!first_cycle_insn_p
- && (GET_CODE (PATTERN (insn)) == ASM_INPUT
- || asm_noperands (PATTERN (insn)) >= 0))
- cost = 1;
- reason = "asm";
+ if (GET_CODE (PATTERN (insn)) == ASM_INPUT
+ || asm_noperands (PATTERN (insn)) >= 0)
+ {
+ reason = "asm";
+ if (!first_cycle_insn_p)
+ cost = 1;
+ }
+ else if (unrecog_insn_for_forw_only_p (insn))
+ {
+ reason = "unrecog insn";
+ if (!first_cycle_insn_p)
+ cost = 1;
+ else
+ {
+ int j = i;
+ while (n > ++j)
+ if (!unrecog_insn_for_forw_only_p (ready_element (&ready, j)))
+ break;
+
+ cost = (j == n) ? 0 : 1;
+ }
+ }
}
else if (sched_pressure != SCHED_PRESSURE_NONE)
{
--
2.17.1
next prev parent reply other threads:[~2023-05-29 10:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-23 8:07 [PATCH] In the ready lists of pipeline, put unrecog insns (such as CLOBBER,USE) at the latest to issue Jin Ma
2023-03-27 17:01 ` [PATCH] In the ready lists of pipeline, put unrecog insns (such as CLOBBER, USE) " Richard Sandiford
2023-04-14 21:38 ` Jeff Law
2023-05-29 10:51 ` Jin Ma [this message]
2023-06-08 1:50 ` [PATCH] In the pipeline, UNRECOG INSN is not executed in advance if it starts a live range Jin Ma
2023-06-09 23:40 ` Jeff Law
2023-06-12 3:38 ` Jin Ma
2023-11-11 18:51 ` Jeff Law
2023-08-14 11:22 ` [PATCH v2] In the pipeline, USE or CLOBBER should delay execution if it starts a new " Jin Ma
2023-08-29 8:00 ` Jin Ma
2023-11-11 20:12 ` Jeff Law
2023-11-12 17:41 ` Xi Ruoyao
2023-11-12 18:02 ` Jeff Law
2023-11-12 18:11 ` Xi Ruoyao
2023-11-13 2:16 ` Jin Ma
2023-11-13 2:28 ` Jeff Law
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