Two fixes for live-out SLP inductions (PR 83857)

Message ID 874lnmx78a.fsf@linaro.org
State New
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  • Two fixes for live-out SLP inductions (PR 83857)
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Commit Message

Richard Sandiford Jan. 16, 2018, 1:29 p.m.
vect_analyze_loop_operations was calling vectorizable_live_operation
for all live-out phis, which led to a bogus ncopies calculation in
the pure SLP case.  I think v_a_l_o should only be passing phis
that are vectorised using normal loop vectorisation, since
vect_slp_analyze_node_operations handles the SLP side (and knows
the correct slp_index and slp_node arguments to pass in, via
vect_analyze_stmt).

With that fixed we hit an older bug that vectorizable_live_operation
didn't handle live-out SLP inductions.  Fixed by using gimple_phi_result
rather than gimple_get_lhs for phis.

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

Richard


2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/83857
	* tree-vect-loop.c (vect_analyze_loop_operations): Don't call
	vectorizable_live_operation for pure SLP statements.
	(vectorizable_live_operation): Handle PHIs.

gcc/testsuite/
	PR tree-optimization/83857
	* gcc.dg/vect/pr83857.c: New test.

Comments

Richard Biener Jan. 16, 2018, 3:09 p.m. | #1
On Tue, Jan 16, 2018 at 2:29 PM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> vect_analyze_loop_operations was calling vectorizable_live_operation

> for all live-out phis, which led to a bogus ncopies calculation in

> the pure SLP case.  I think v_a_l_o should only be passing phis

> that are vectorised using normal loop vectorisation, since

> vect_slp_analyze_node_operations handles the SLP side (and knows

> the correct slp_index and slp_node arguments to pass in, via

> vect_analyze_stmt).

>

> With that fixed we hit an older bug that vectorizable_live_operation

> didn't handle live-out SLP inductions.  Fixed by using gimple_phi_result

> rather than gimple_get_lhs for phis.

>

> Tested on aarch64-linux-gnu.  OK to install?


Ok.

Richard.

> Richard

>

>

> 2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>

>

> gcc/

>         PR tree-optimization/83857

>         * tree-vect-loop.c (vect_analyze_loop_operations): Don't call

>         vectorizable_live_operation for pure SLP statements.

>         (vectorizable_live_operation): Handle PHIs.

>

> gcc/testsuite/

>         PR tree-optimization/83857

>         * gcc.dg/vect/pr83857.c: New test.

>

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

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

> --- gcc/tree-vect-loop.c        2018-01-13 18:02:00.950360196 +0000

> +++ gcc/tree-vect-loop.c        2018-01-16 13:24:33.022528019 +0000

> @@ -1851,7 +1851,10 @@ vect_analyze_loop_operations (loop_vec_i

>                 ok = vectorizable_reduction (phi, NULL, NULL, NULL, NULL);

>              }

>

> -         if (ok && STMT_VINFO_LIVE_P (stmt_info))

> +         /* SLP PHIs are tested by vect_slp_analyze_node_operations.  */

> +         if (ok

> +             && STMT_VINFO_LIVE_P (stmt_info)

> +             && !PURE_SLP_STMT (stmt_info))

>             ok = vectorizable_live_operation (phi, NULL, NULL, -1, NULL);

>

>            if (!ok)

> @@ -8217,7 +8220,11 @@ vectorizable_live_operation (gimple *stm

>        gcc_assert (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo));

>

>        /* Get the correct slp vectorized stmt.  */

> -      vec_lhs = gimple_get_lhs (SLP_TREE_VEC_STMTS (slp_node)[vec_entry]);

> +      gimple *vec_stmt = SLP_TREE_VEC_STMTS (slp_node)[vec_entry];

> +      if (gphi *phi = dyn_cast <gphi *> (vec_stmt))

> +       vec_lhs = gimple_phi_result (phi);

> +      else

> +       vec_lhs = gimple_get_lhs (vec_stmt);

>

>        /* Get entry to use.  */

>        bitstart = bitsize_int (vec_index);

> Index: gcc/testsuite/gcc.dg/vect/pr83857.c

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

> --- /dev/null   2018-01-15 18:48:25.844002736 +0000

> +++ gcc/testsuite/gcc.dg/vect/pr83857.c 2018-01-16 13:24:33.021528058 +0000

> @@ -0,0 +1,30 @@

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

> +/* { dg-additional-options "-ffast-math" } */

> +

> +#define N 100

> +

> +double __attribute__ ((noinline, noclone))

> +f (double *x, double y)

> +{

> +  double a = 0;

> +  for (int i = 0; i < N; ++i)

> +    {

> +      a += y;

> +      x[i * 2] += a;

> +      x[i * 2 + 1] += a;

> +    }

> +  return a - y;

> +}

> +

> +double x[N * 2];

> +

> +int

> +main (void)

> +{

> +  if (f (x, 5) != (N - 1) * 5)

> +    __builtin_abort ();

> +  return 0;

> +}

> +

> +/* { dg-final { scan-tree-dump "Loop contains only SLP stmts" "vect" { target vect_double } } } */

> +/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { target vect_double } } } */

Patch

Index: gcc/tree-vect-loop.c
===================================================================
--- gcc/tree-vect-loop.c	2018-01-13 18:02:00.950360196 +0000
+++ gcc/tree-vect-loop.c	2018-01-16 13:24:33.022528019 +0000
@@ -1851,7 +1851,10 @@  vect_analyze_loop_operations (loop_vec_i
 		ok = vectorizable_reduction (phi, NULL, NULL, NULL, NULL);
             }
 
-	  if (ok && STMT_VINFO_LIVE_P (stmt_info))
+	  /* SLP PHIs are tested by vect_slp_analyze_node_operations.  */
+	  if (ok
+	      && STMT_VINFO_LIVE_P (stmt_info)
+	      && !PURE_SLP_STMT (stmt_info))
 	    ok = vectorizable_live_operation (phi, NULL, NULL, -1, NULL);
 
           if (!ok)
@@ -8217,7 +8220,11 @@  vectorizable_live_operation (gimple *stm
       gcc_assert (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo));
 
       /* Get the correct slp vectorized stmt.  */
-      vec_lhs = gimple_get_lhs (SLP_TREE_VEC_STMTS (slp_node)[vec_entry]);
+      gimple *vec_stmt = SLP_TREE_VEC_STMTS (slp_node)[vec_entry];
+      if (gphi *phi = dyn_cast <gphi *> (vec_stmt))
+	vec_lhs = gimple_phi_result (phi);
+      else
+	vec_lhs = gimple_get_lhs (vec_stmt);
 
       /* Get entry to use.  */
       bitstart = bitsize_int (vec_index);
Index: gcc/testsuite/gcc.dg/vect/pr83857.c
===================================================================
--- /dev/null	2018-01-15 18:48:25.844002736 +0000
+++ gcc/testsuite/gcc.dg/vect/pr83857.c	2018-01-16 13:24:33.021528058 +0000
@@ -0,0 +1,30 @@ 
+/* { dg-do run } */
+/* { dg-additional-options "-ffast-math" } */
+
+#define N 100
+
+double __attribute__ ((noinline, noclone))
+f (double *x, double y)
+{
+  double a = 0;
+  for (int i = 0; i < N; ++i)
+    {
+      a += y;
+      x[i * 2] += a;
+      x[i * 2 + 1] += a;
+    }
+  return a - y;
+}
+
+double x[N * 2];
+
+int
+main (void)
+{
+  if (f (x, 5) != (N - 1) * 5)
+    __builtin_abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump "Loop contains only SLP stmts" "vect" { target vect_double } } } */
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { target vect_double } } } */