Re: [PATCH PR81620]Don't set has_max_use_after flag for store-store chain

[Richard Biener]

On Mon, Jul 31, 2017 at 4:12 PM, Bin Cheng  wrote:
> Hi,
> This simple patch fixes the ICE by not setting has_max_use_after flag for
> store-store chain because there is no use at all.
> Bootstrap and test on x86_64 and AArch64 ongoing.  Is it OK if no failure?

Ok.

Richard.

> Thanks,
> bin
> 2017-07-31  Bin Cheng  
>
> PR tree-optimization/81620
> * tree-predcom.c (add_ref_to_chain): Don't set has_max_use_after
> for store-store chain.
>
> gcc/testsuite/ChangeLog
> 2017-07-31  Bin Cheng  
>
> PR tree-optimization/81620
> * gcc.dg/tree-ssa/pr81620-1.c: New.
> * gcc.dg/tree-ssa/pr81620-2.c: New.

[PATCH PR81620]Don't set has_max_use_after flag for store-store chain

[Bin Cheng]

Hi,
This simple patch fixes the ICE by not setting has_max_use_after flag for
store-store chain because there is no use at all.
Bootstrap and test on x86_64 and AArch64 ongoing.  Is it OK if no failure?

Thanks,
bin
2017-07-31  Bin Cheng  

PR tree-optimization/81620
* tree-predcom.c (add_ref_to_chain): Don't set has_max_use_after
for store-store chain.

gcc/testsuite/ChangeLog
2017-07-31  Bin Cheng  

PR tree-optimization/81620
* gcc.dg/tree-ssa/pr81620-1.c: New.
* gcc.dg/tree-ssa/pr81620-2.c: New.From 4e8f67bb1cc09ef475f9cfbb8e847f9f422c3e44 Mon Sep 17 00:00:00 2001
From: Bin Cheng 
Date: Mon, 31 Jul 2017 10:24:07 +0100
Subject: [PATCH 1/2] pr81620-20170731.txt

---
 gcc/testsuite/gcc.dg/tree-ssa/pr81620-1.c | 20 
 gcc/testsuite/gcc.dg/tree-ssa/pr81620-2.c | 25 +
 gcc/tree-predcom.c|  4 +++-
 3 files changed, 48 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr81620-1.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr81620-2.c

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr81620-1.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr81620-1.c
new file mode 100644
index 000..f8f2dd8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr81620-1.c
@@ -0,0 +1,20 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -fno-tree-loop-vectorize -fdump-tree-pcom-details" } */
+
+int a[7];
+char b;
+void abort (void);
+
+int main() {
+  b = 4;
+  for (; b; b--) {
+a[b] = b;
+a[b + 2] = 1;
+  }
+  if (a[0] != 0 || a[1] != 1 || a[2] != 2
+  || a[3] != 1 || a[4] != 1 || a[5] != 1 || a[6] != 1)
+abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Store-stores chain" 1 "pcom" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr81620-2.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr81620-2.c
new file mode 100644
index 000..85a8e35
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr81620-2.c
@@ -0,0 +1,25 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -fno-tree-loop-vectorize -fdump-tree-pcom-details" } */
+
+int a[200];
+char b;
+void abort (void);
+
+int main() {
+  int i;
+  b = 100;
+  for (; b; b--) {
+a[b] = 2;
+a[b + 2] = 1;
+  }
+
+  if (a[0] != 0 || a[1] != 2 || a[2] != 2)
+abort ();
+  for (i = 3; i < 103; i++)
+if (a[i] != 1)
+abort ();
+
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Store-stores chain" 1 "pcom" } } */
diff --git a/gcc/tree-predcom.c b/gcc/tree-predcom.c
index a4011bf..f7a57a4 100644
--- a/gcc/tree-predcom.c
+++ b/gcc/tree-predcom.c
@@ -1069,7 +1069,9 @@ add_ref_to_chain (chain_p chain, dref ref)
   chain->has_max_use_after = false;
 }
 
-  if (ref->distance == chain->length
+  /* Don't set the flag for store-store chain since there is no use.  */
+  if (chain->type != CT_STORE_STORE
+  && ref->distance == chain->length
   && ref->pos > root->pos)
 chain->has_max_use_after = true;
 
-- 
1.9.1