Another fix for single-element permutes (PR 84265)

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  • Another fix for single-element permutes (PR 84265)
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Richard Sandiford Feb. 8, 2018, 1:29 p.m.
PR83753 was about a case in which we ended up trying to "vectorise"
a group of loads ore stores using single-element vectors.  The problem
was that we were classifying the load or store as VMAT_CONTIGUOUS_PERMUTE
rather than VMAT_CONTIGUOUS, even though it doesn't make sense to permute
a single-element vector.

In that PR it was enough to change get_group_load_store_type,
because vectorisation ended up being unprofitable and so we didn't
take things further.  But when vectorisation is profitable, the same
fix is needed in vectorizable_load and vectorizable_store.

Tested on aarch64-linux-gnu, aarch64_be-elf and x86_64-linux-gnu.
OK to install?

Richard


2018-02-08  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/84265
	* tree-vect-stmts.c (vectorizable_store): Don't treat
	VMAT_CONTIGUOUS accesses as grouped.
	(vectorizable_load): Likewise.

gcc/testsuite/
	PR tree-optimization/84265
	* gcc.dg/vect/pr84265.c: New test.

Comments

Richard Biener Feb. 8, 2018, 3:10 p.m. | #1
On Thu, Feb 8, 2018 at 2:29 PM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> PR83753 was about a case in which we ended up trying to "vectorise"

> a group of loads ore stores using single-element vectors.  The problem

> was that we were classifying the load or store as VMAT_CONTIGUOUS_PERMUTE

> rather than VMAT_CONTIGUOUS, even though it doesn't make sense to permute

> a single-element vector.

>

> In that PR it was enough to change get_group_load_store_type,

> because vectorisation ended up being unprofitable and so we didn't

> take things further.  But when vectorisation is profitable, the same

> fix is needed in vectorizable_load and vectorizable_store.

>

> Tested on aarch64-linux-gnu, aarch64_be-elf and x86_64-linux-gnu.

> OK to install?


OK.

Richard.

> Richard

>

>

> 2018-02-08  Richard Sandiford  <richard.sandiford@linaro.org>

>

> gcc/

>         PR tree-optimization/84265

>         * tree-vect-stmts.c (vectorizable_store): Don't treat

>         VMAT_CONTIGUOUS accesses as grouped.

>         (vectorizable_load): Likewise.

>

> gcc/testsuite/

>         PR tree-optimization/84265

>         * gcc.dg/vect/pr84265.c: New test.

>

> Index: gcc/tree-vect-stmts.c

> ===================================================================

> --- gcc/tree-vect-stmts.c       2018-01-30 09:45:27.710764075 +0000

> +++ gcc/tree-vect-stmts.c       2018-02-08 13:26:39.242566948 +0000

> @@ -6214,7 +6214,8 @@ vectorizable_store (gimple *stmt, gimple

>      }

>

>    grouped_store = (STMT_VINFO_GROUPED_ACCESS (stmt_info)

> -                  && memory_access_type != VMAT_GATHER_SCATTER);

> +                  && memory_access_type != VMAT_GATHER_SCATTER

> +                  && (slp || memory_access_type != VMAT_CONTIGUOUS));

>    if (grouped_store)

>      {

>        first_stmt = GROUP_FIRST_ELEMENT (stmt_info);

> @@ -7696,7 +7697,8 @@ vectorizable_load (gimple *stmt, gimple_

>        return true;

>      }

>

> -  if (memory_access_type == VMAT_GATHER_SCATTER)

> +  if (memory_access_type == VMAT_GATHER_SCATTER

> +      || (!slp && memory_access_type == VMAT_CONTIGUOUS))

>      grouped_load = false;

>

>    if (grouped_load)

> Index: gcc/testsuite/gcc.dg/vect/pr84265.c

> ===================================================================

> --- /dev/null   2018-02-08 11:17:10.862716283 +0000

> +++ gcc/testsuite/gcc.dg/vect/pr84265.c 2018-02-08 13:26:39.240567025 +0000

> @@ -0,0 +1,23 @@

> +/* { dg-do compile } */

> +

> +struct a

> +{

> +  unsigned long b;

> +  unsigned long c;

> +  int d;

> +  int *e;

> +  char f;

> +};

> +

> +struct

> +{

> +  int g;

> +  struct a h[];

> +} i;

> +

> +int j, k;

> +void l ()

> +{

> +  for (; k; k++)

> +    j += (int) (i.h[k].c - i.h[k].b);

> +}

Patch

Index: gcc/tree-vect-stmts.c
===================================================================
--- gcc/tree-vect-stmts.c	2018-01-30 09:45:27.710764075 +0000
+++ gcc/tree-vect-stmts.c	2018-02-08 13:26:39.242566948 +0000
@@ -6214,7 +6214,8 @@  vectorizable_store (gimple *stmt, gimple
     }
 
   grouped_store = (STMT_VINFO_GROUPED_ACCESS (stmt_info)
-		   && memory_access_type != VMAT_GATHER_SCATTER);
+		   && memory_access_type != VMAT_GATHER_SCATTER
+		   && (slp || memory_access_type != VMAT_CONTIGUOUS));
   if (grouped_store)
     {
       first_stmt = GROUP_FIRST_ELEMENT (stmt_info);
@@ -7696,7 +7697,8 @@  vectorizable_load (gimple *stmt, gimple_
       return true;
     }
 
-  if (memory_access_type == VMAT_GATHER_SCATTER)
+  if (memory_access_type == VMAT_GATHER_SCATTER
+      || (!slp && memory_access_type == VMAT_CONTIGUOUS))
     grouped_load = false;
 
   if (grouped_load)
Index: gcc/testsuite/gcc.dg/vect/pr84265.c
===================================================================
--- /dev/null	2018-02-08 11:17:10.862716283 +0000
+++ gcc/testsuite/gcc.dg/vect/pr84265.c	2018-02-08 13:26:39.240567025 +0000
@@ -0,0 +1,23 @@ 
+/* { dg-do compile } */
+
+struct a
+{
+  unsigned long b;
+  unsigned long c;
+  int d;
+  int *e;
+  char f;
+};
+
+struct
+{
+  int g;
+  struct a h[];
+} i;
+
+int j, k;
+void l ()
+{
+  for (; k; k++)
+    j += (int) (i.h[k].c - i.h[k].b);
+}