re PR tree-optimization/92819 (Worse code generated on avx2 due to simplify_vector_constructor)

2019-12-06  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/92819
	* match.pd (VEC_PERM_EXPR -> BIT_INSERT_EXPR): Handle inserts
	into the last lane.  For two-element vectors try inserting
	into the last lane when inserting into the first fails.

	* gcc.target/i386/pr92819-1.c: New testcase.
	* gcc.target/i386/pr92803.c: Adjust.

From-SVN: r279033

gcc/ChangeLog

+2019-12-06  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/92819
+	* match.pd (VEC_PERM_EXPR -> BIT_INSERT_EXPR): Handle inserts
+	into the last lane.  For two-element vectors try inserting
+	into the last lane when inserting into the first fails.
+
 2019-12-06  Jakub Jelinek  <jakub@redhat.com>
 
 	* common.opt (fprofile-partial-training): Terminate description with

gcc/match.pd

@@ -6032,7 +6032,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 		|| TREE_CODE (cop1) == VECTOR_CST
 		|| TREE_CODE (cop1) == CONSTRUCTOR))
           {
-	    if (sel.series_p (1, 1, nelts + 1, 1))
+	    bool insert_first_p = sel.series_p (1, 1, nelts + 1, 1);
+	    if (insert_first_p)
 	      {
 	        /* After canonicalizing the first elt to come from the
 		   first vector we only can insert the first elt from
@@ -6041,13 +6042,19 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 		if ((ins = fold_read_from_vector (cop0, sel[0])))
 		  op0 = op1;
 	      }
-	    else
+	    /* The above can fail for two-element vectors which always
+	       appear to insert the first element, so try inserting
+	       into the second lane as well.  For more than two
+	       elements that's wasted time.  */
+	    if (!insert_first_p || (!ins && maybe_eq (nelts, 2u)))
 	      {
 	        unsigned int encoded_nelts = sel.encoding ().encoded_nelts ();
 		for (at = 0; at < encoded_nelts; ++at)
 		  if (maybe_ne (sel[at], at))
 		    break;
-		if (at < encoded_nelts && sel.series_p (at + 1, 1, at + 1, 1))
+		if (at < encoded_nelts
+		    && (known_eq (at + 1, nelts)
+			|| sel.series_p (at + 1, 1, at + 1, 1)))
 		  {
 		    if (known_lt (poly_uint64 (sel[at]), nelts))
 		      ins = fold_read_from_vector (cop0, sel[at]);

gcc/testsuite/ChangeLog

+2019-12-06  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/92819
+	* gcc.target/i386/pr92819-1.c: New testcase.
+	* gcc.target/i386/pr92803.c: Adjust.
+
 2019-12-05  Martin Sebor  <msebor@redhat.com>
 
 	PR testsuite/92829

gcc/testsuite/gcc.target/i386/pr92803.c

@@ -31,8 +31,10 @@ barf (v8sf x)
   return (v4sf) { x[4], x[5], 1.0f, 2.0f };
 }
 
-/* We expect all CTORs to turn into permutes, the FP converting ones
+/* For bar we do two inserts, first zero, then convert, then insert *p.  } */
+/* { dg-final { scan-tree-dump-times "BIT_INSERT_EXPR" 2 "forwprop1" } } */
+/* We expect all other CTORs to turn into permutes, the FP converting ones
    to two each with the one with constants possibly elided in the future
    by converting 3.0f and 1.0f "back" to integers.  */
-/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 6 "forwprop1" } } */
-/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 5 "forwprop1" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 4 "forwprop1" } } */
+/* { dg-final { scan-tree-dump-times "VEC_PERM_EXPR" 3 "forwprop1" { xfail *-*-* } } } */

gcc/testsuite/gcc.target/i386/pr92819-1.c

+/* { dg-do compile } */
+/* { dg-options "-O -msse2 -fdump-tree-forwprop1" } */
+
+typedef double v2df __attribute__((vector_size (16)));
+
+v2df
+foo (v2df x, double *p)
+{
+  return (v2df) { x[0], *p };
+}
+
+v2df
+bar (v2df x, double *p)
+{
+  return (v2df) { *p, x[1] };
+}
+
+/* { dg-final { scan-tree-dump-times "BIT_INSERT_EXPR" 2 "forwprop1" } } */
+/* { dg-final { scan-assembler "movhpd" } } */
+/* { dg-final { scan-assembler "movlpd" } } */