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* [gcc/devel/autopar_devel] rs6000: Refine RTL unroll hook for small loops
@ 2020-08-22 23:40 Giuliano Belinassi
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From: Giuliano Belinassi @ 2020-08-22 23:40 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:4d0ff0ab72f3adfd40b0248c599ae5a4cb8ba8a6
commit 4d0ff0ab72f3adfd40b0248c599ae5a4cb8ba8a6
Author: guojiufu <guojiufu@linux.ibm.com>
Date: Wed Jul 15 16:07:47 2020 +0800
rs6000: Refine RTL unroll hook for small loops
For very small loops (< 6 insns), it would be fine to unroll 4
times to run fast with less latency and better cache usage. Like
below loops:
while (i) a[--i] = NULL; while (p < e) *d++ = *p++;
With this patch enhances, we could see some performance improvement
for some workloads(e.g. SPEC2017).
2020-07-13 Jiufu Guo <guojiufu@cn.ibm.com>
* config/rs6000/rs6000.c (rs6000_loop_unroll_adjust): Refine hook.
Diff:
---
gcc/config/rs6000/rs6000.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index dda51d5877a..c5c3300c59c 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -5212,13 +5212,14 @@ rs6000_loop_unroll_adjust (unsigned nunroll, struct loop *loop)
{
if (unroll_only_small_loops)
{
- /* TODO: This is hardcoded to 10 right now. It can be refined, for
- example we may want to unroll very small loops more times (4 perhaps).
- We also should use a PARAM for this. */
+ /* TODO: These are hardcoded values right now. We probably should use
+ a PARAM here. */
+ if (loop->ninsns <= 6)
+ return MIN (4, nunroll);
if (loop->ninsns <= 10)
return MIN (2, nunroll);
- else
- return 0;
+
+ return 0;
}
return nunroll;
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