Handle SLP of call pattern statements

We couldn't vectorise:

  for (int j = 0; j < n; ++j)
    {
      for (int i = 0; i < 16; ++i)
	a[i] = (b[i] + c[i]) >> 1;
      a += step;
      b += step;
      c += step;
    }

at -O3 because cunrolli unrolled the inner loop and SLP couldn't handle
AVG_FLOOR patterns (see also PR86504).  The problem was some overly
strict checking of pattern statements compared to normal statements
in vect_get_and_check_slp_defs:

          switch (gimple_code (def_stmt))
            {
            case GIMPLE_PHI:
            case GIMPLE_ASSIGN:
	      break;

	    default:
	      if (dump_enabled_p ())
		dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
				 "unsupported defining stmt:\n");
	      return -1;
            }

The easy fix would have been to add GIMPLE_CALL to the switch,
but I don't think the switch is doing anything useful.  We only create
pattern statements that the rest of the vectoriser can handle, and the
other checks in this function and elsewhere check whether SLP is possible.

I'm also not sure why:

          if (!first && !oprnd_info->first_pattern
	      /* Allow different pattern state for the defs of the
		 first stmt in reduction chains.  */
	      && (oprnd_info->first_dt != vect_reduction_def

is necessary.  All that should matter is that the statements in the
node are "similar enough".  It turned out to be quite hard to find a
convincing example that used a mixture of pattern and non-pattern
statements, so bb-slp-pow-1.c is the best I could come up with.
But it does show that the combination of "xi * xi" statements and
"pow (xj, 2) -> xj * xj" patterns are handled correctly.

The patch therefore just removes the whole if block.

The loop also needed commutative swapping to be extended to at least
AVG_FLOOR.

This gives +3.9% on 525.x264_r at -O3.

2018-08-03  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* internal-fn.h (first_commutative_argument): Declare.
	* internal-fn.c (first_commutative_argument): New function.
	* tree-vect-slp.c (vect_get_and_check_slp_defs): Remove extra
	restrictions for pattern statements.  Use first_commutative_argument
	to look for commutative operands in calls to internal functions.

gcc/testsuite/
	* gcc.dg/vect/bb-slp-over-widen-1.c: Expect AVG_FLOOR to be used
	on vect_avg_qi targets.
	* gcc.dg/vect/bb-slp-over-widen-2.c: Likewise.
	* gcc.dg/vect/bb-slp-pow-1.c: New test.
	* gcc.dg/vect/vect-avg-15.c: Likewise.

From-SVN: r263290

1 files changed, 36 insertions, 0 deletions

diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
index 8ede9ca..34d4f9e 100644
--- a/gcc/internal-fn.c
+++ b/gcc/internal-fn.c
@@ -3183,6 +3183,42 @@ direct_internal_fn_supported_p (internal_fn fn, tree type,
   return direct_internal_fn_supported_p (fn, tree_pair (type, type), opt_type);
 }
 
+/* If FN is commutative in two consecutive arguments, return the
+   index of the first, otherwise return -1.  */
+
+int
+first_commutative_argument (internal_fn fn)
+{
+  switch (fn)
+    {
+    case IFN_FMA:
+    case IFN_FMS:
+    case IFN_FNMA:
+    case IFN_FNMS:
+    case IFN_AVG_FLOOR:
+    case IFN_AVG_CEIL:
+    case IFN_FMIN:
+    case IFN_FMAX:
+      return 0;
+
+    case IFN_COND_ADD:
+    case IFN_COND_MUL:
+    case IFN_COND_MIN:
+    case IFN_COND_MAX:
+    case IFN_COND_AND:
+    case IFN_COND_IOR:
+    case IFN_COND_XOR:
+    case IFN_COND_FMA:
+    case IFN_COND_FMS:
+    case IFN_COND_FNMA:
+    case IFN_COND_FNMS:
+      return 1;
+
+    default:
+      return -1;
+    }
+}
+
 /* Return true if IFN_SET_EDOM is supported.  */
 
 bool