diff mbox series

vect: Fix missed gather load opportunity

Message ID mptilln4uo0.fsf@arm.com
State Accepted, archived
Headers
Series vect: Fix missed gather load opportunity |

Checks

Context Check Description
snail/gcc-patches-check success Github commit url

Commit Message

Richard Sandiford Sept. 16, 2022, 7:58 a.m. UTC 
  While writing a testcase for PR106794, I noticed that we failed
to vectorise the testcase in the patch for SVE.  The code that
recognises gather loads tries to optimise the point at which
the offset is calculated, to avoid unnecessary extensions or
truncations:

	  /* Don't include the conversion if the target is happy with
	     the current offset type.  */

But breaking only makes sense if we're at an SSA_NAME (which could
then be vectorised).  We shouldn't break on a conversion embedded
in a generic expression.

Tested on aarch64-linux-gnu & x86_64-linux-gnu.  OK to install?

Richard


gcc/
	* tree-vect-data-refs.cc (vect_check_gather_scatter): Restrict
	early-out optimisation to SSA_NAMEs.

gcc/testsuite/
	* gcc.dg/vect/vect-gather-5.c: New test.
---
 gcc/testsuite/gcc.dg/vect/vect-gather-5.c | 42 +++++++++++++++++++++++
 gcc/tree-vect-data-refs.cc                |  1 +
 2 files changed, 43 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/vect/vect-gather-5.c

Comments

Richard Biener Sept. 17, 2022, 5:03 a.m. UTC | #1 
On Fri, 16 Sep 2022, Richard Sandiford wrote:

> While writing a testcase for PR106794, I noticed that we failed
> to vectorise the testcase in the patch for SVE.  The code that
> recognises gather loads tries to optimise the point at which
> the offset is calculated, to avoid unnecessary extensions or
> truncations:
>
> 	  /* Don't include the conversion if the target is happy with
> 	     the current offset type.  */
>
> But breaking only makes sense if we're at an SSA_NAME (which could
> then be vectorised).  We shouldn't break on a conversion embedded
> in a generic expression.
>
> Tested on aarch64-linux-gnu & x86_64-linux-gnu.  OK to install?

OK,

Thanks,
Richard.

> Richard
>
>
> gcc/
> 	* tree-vect-data-refs.cc (vect_check_gather_scatter): Restrict
> 	early-out optimisation to SSA_NAMEs.
>
> gcc/testsuite/
> 	* gcc.dg/vect/vect-gather-5.c: New test.
> ---
> gcc/testsuite/gcc.dg/vect/vect-gather-5.c | 42 +++++++++++++++++++++++
> gcc/tree-vect-data-refs.cc                |  1 +
> 2 files changed, 43 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-gather-5.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-gather-5.c b/gcc/testsuite/gcc.dg/vect/vect-gather-5.c
> new file mode 100644
> index 00000000000..8b5074bba88
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-gather-5.c
> @@ -0,0 +1,42 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-O3" } */
> +
> +#ifdef __aarch64__
> +#pragma GCC target "+sve"
> +#endif
> +
> +long a[100], b[100], c[100];
> +
> +void g1 ()
> +{
> +  for (int i = 0; i < 100; i += 2)
> +    {
> +      c[i] += a[b[i]] + 1;
> +      c[i + 1] += a[b[i + 1]] + 2;
> +    }
> +}
> +
> +long g2 ()
> +{
> +  long res = 0;
> +  for (int i = 0; i < 100; i += 2)
> +    {
> +      res += a[b[i + 1]];
> +      res += a[b[i]];
> +    }
> +  return res;
> +}
> +
> +long g3 ()
> +{
> +  long res = 0;
> +  for (int i = 0; i < 100; i += 2)
> +    {
> +      res += a[b[i]];
> +      res += a[b[i + 1]];
> +    }
> +  return res;
> +}
> +
> +/* { dg-final { scan-tree-dump-times {add new stmt[^\n]*GATHER_LOAD} 3 "vect" { target aarch64*-*-* } } } */
> +/* { dg-final { scan-tree-dump-not {add new stmt[^\n]*VEC_PERM_EXPR} "vect" { target aarch64*-*-* } } } */
> diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc
> index b279a82551e..e03b50498d1 100644
> --- a/gcc/tree-vect-data-refs.cc
> +++ b/gcc/tree-vect-data-refs.cc
> @@ -4151,6 +4151,7 @@ vect_check_gather_scatter (stmt_vec_info stmt_info, loop_vec_info loop_vinfo,
> 	  /* Don't include the conversion if the target is happy with
> 	     the current offset type.  */
> 	  if (use_ifn_p
> +	      && TREE_CODE (off) == SSA_NAME
> 	      && !POINTER_TYPE_P (TREE_TYPE (off))
> 	      && vect_gather_scatter_fn_p (loop_vinfo, DR_IS_READ (dr),
> 					   masked_p, vectype, memory_type,
> -- 
> 2.25.1
>
>
diff mbox series

Patch

diff --git a/gcc/testsuite/gcc.dg/vect/vect-gather-5.c b/gcc/testsuite/gcc.dg/vect/vect-gather-5.c
new file mode 100644
index 00000000000..8b5074bba88
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-gather-5.c
@@ -0,0 +1,42 @@ 
+/* { dg-do compile } */
+/* { dg-additional-options "-O3" } */
+
+#ifdef __aarch64__
+#pragma GCC target "+sve"
+#endif
+
+long a[100], b[100], c[100];
+
+void g1 ()
+{
+  for (int i = 0; i < 100; i += 2)
+    {
+      c[i] += a[b[i]] + 1;
+      c[i + 1] += a[b[i + 1]] + 2;
+    }
+}
+
+long g2 ()
+{
+  long res = 0;
+  for (int i = 0; i < 100; i += 2)
+    {
+      res += a[b[i + 1]];
+      res += a[b[i]];
+    }
+  return res;
+}
+
+long g3 ()
+{
+  long res = 0;
+  for (int i = 0; i < 100; i += 2)
+    {
+      res += a[b[i]];
+      res += a[b[i + 1]];
+    }
+  return res;
+}
+
+/* { dg-final { scan-tree-dump-times {add new stmt[^\n]*GATHER_LOAD} 3 "vect" { target aarch64*-*-* } } } */
+/* { dg-final { scan-tree-dump-not {add new stmt[^\n]*VEC_PERM_EXPR} "vect" { target aarch64*-*-* } } } */
diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc
index b279a82551e..e03b50498d1 100644
--- a/gcc/tree-vect-data-refs.cc
+++ b/gcc/tree-vect-data-refs.cc
@@ -4151,6 +4151,7 @@  vect_check_gather_scatter (stmt_vec_info stmt_info, loop_vec_info loop_vinfo,
 	  /* Don't include the conversion if the target is happy with
 	     the current offset type.  */
 	  if (use_ifn_p
+	      && TREE_CODE (off) == SSA_NAME
 	      && !POINTER_TYPE_P (TREE_TYPE (off))
 	      && vect_gather_scatter_fn_p (loop_vinfo, DR_IS_READ (dr),
 					   masked_p, vectype, memory_type,