[PATCH] PR90930 followup

[Richard Biener]

This avoids going back-and-forth from linearized to widened
expressions in reassoc twice and only rewrites expressions
according to reassoc-width in the last reassoc pass.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2019-06-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/90930
	* tree-ssa-reassoc.c (reassociate_bb): Only rewrite expression
	into parallel form in the last pass instance.

	* gcc.dg/tree-ssa/reassoc-24.c: Adjust.
	* gcc.dg/tree-ssa/reassoc-25.c: Likewise.

Index: gcc/tree-ssa-reassoc.c
===================================================================
--- gcc/tree-ssa-reassoc.c	(revision 272636)
+++ gcc/tree-ssa-reassoc.c	(working copy)
@@ -6013,12 +6013,7 @@ reassociate_bb (basic_block bb)
 		{
 		  machine_mode mode = TYPE_MODE (TREE_TYPE (lhs));
 		  int ops_num = ops.length ();
-		  int width = get_reassociation_width (ops_num, rhs_code, mode);
-
-		  if (dump_file && (dump_flags & TDF_DETAILS))
-		    fprintf (dump_file,
-			     "Width = %d was chosen for reassociation\n", width);
-
+		  int width;
 
 		  /* For binary bit operations, if there are at least 3
 		     operands and the last last operand in OPS is a constant,
@@ -6032,10 +6027,21 @@ reassociate_bb (basic_block bb)
 		      && TREE_CODE (ops.last ()->op) == INTEGER_CST)
 		    std::swap (*ops[0], *ops[ops_num - 1]);
 
-		  if (width > 1
-		      && ops.length () > 3)
-		    rewrite_expr_tree_parallel (as_a <gassign *> (stmt),
-						width, ops);
+		  /* Only rewrite the expression tree to parallel in the
+		     last reassoc pass to avoid useless work back-and-forth
+		     with initial linearization.  */
+		  if (!reassoc_insert_powi_p
+		      && ops.length () > 3
+		      && (width = get_reassociation_width (ops_num, rhs_code,
+							   mode)) > 1)
+		    {
+		      if (dump_file && (dump_flags & TDF_DETAILS))
+			fprintf (dump_file,
+				 "Width = %d was chosen for reassociation\n",
+				 width);
+		      rewrite_expr_tree_parallel (as_a <gassign *> (stmt),
+						  width, ops);
+		    }
 		  else
                     {
                       /* When there are three operands left, we want
Index: gcc/testsuite/gcc.dg/tree-ssa/reassoc-24.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/reassoc-24.c	(revision 272636)
+++ gcc/testsuite/gcc.dg/tree-ssa/reassoc-24.c	(working copy)
@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-O2 --param tree-reassoc-width=2 -fdump-tree-reassoc1" } */
+/* { dg-options "-O2 --param tree-reassoc-width=2 -fdump-tree-reassoc2" } */
 
 unsigned int
 foo (void)
@@ -21,4 +21,4 @@ foo (void)
 
 /* Verify there are two pairs of __asm__ statements with no
    intervening stmts.  */
-/* { dg-final { scan-tree-dump-times "__asm__\[^;\n]*;\n *__asm__" 2 "reassoc1"} } */
+/* { dg-final { scan-tree-dump-times "__asm__\[^;\n]*;\n *__asm__" 2 "reassoc2"} } */
Index: gcc/testsuite/gcc.dg/tree-ssa/reassoc-25.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/reassoc-25.c	(revision 272636)
+++ gcc/testsuite/gcc.dg/tree-ssa/reassoc-25.c	(working copy)
@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-O2 --param tree-reassoc-width=3 -fdump-tree-reassoc1-details" } */
+/* { dg-options "-O2 --param tree-reassoc-width=3 -fdump-tree-reassoc2-details" } */
 
 unsigned int
 foo (int a, int b, int c, int d)
@@ -15,4 +15,4 @@ foo (int a, int b, int c, int d)
 }
 
 /* Verify reassociation width was chosen to be 2.  */
-/* { dg-final { scan-tree-dump-times "Width = 2" 1 "reassoc1"} } */
+/* { dg-final { scan-tree-dump-times "Width = 2" 1 "reassoc2"} } */