[PHIOPT/MATCH] Remove the statement to move if not used

Instead of waiting for DCE to remove the unused statement,
and maybe optimize another conditional, it is better if
we don't move the statement and have the statement
removed.

OK? Bootstrapped and tested on x86_64-linux-gnu.

Changes from v1:
* v2: Change the order of insertation and check to see if the lhs
  is used rather than see if the lhs was used in the sequence.

gcc/ChangeLog:

	* tree-ssa-phiopt.c (match_simplify_replacement): Move
	insert of the sequence before the movement of the
	statement. Check if to see if the statement is used
	outside of the original phi to see if we should move it.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr96928-1.c: Update to similar as pr96928.c.

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
index 2e86620da11d11a7b42c7f3592be29f32d67402b..9e505ac9900b8d45d2c6533ccbfc3b7a3b141d44 100644 (file)
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
@@ -2,7 +2,10 @@
 /* { dg-do compile } */
 /* { dg-options "-O2 -fdump-tree-phiopt2 -fdump-tree-optimized" } */
 /* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2" } } */
-/* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" } } */
+/* The following check is done at optimized because a ^ (~b) is rewritten as ~(a^b)
+   and in the case of match.pd optimizing these ?:, the ~ is moved out already
+   by the time we get to phiopt2. */
+/* { dg-final { scan-tree-dump-times "c_\[0-9]*\\\(D\\\) \\\^" 1 "optimized" } } */
 /* { dg-final { scan-tree-dump-times " = ~" 1 "optimized" } } */
 /* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5 "phiopt2" } } */
 /* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */

diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
index 7a98b7afdf16577142c9f777b9815a90176e341d..c6adbbd28a012a94b29ffbd8334628f0db64a119 100644 (file)
--- a/gcc/tree-ssa-phiopt.c
+++ b/gcc/tree-ssa-phiopt.c
@@ -1020,7 +1020,16 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
     return false;
 
   gsi = gsi_last_bb (cond_bb);
-  if (stmt_to_move)
+  /* Insert the sequence generated from gimple_simplify_phiopt.  */
+  if (seq)
+    gsi_insert_seq_before (&gsi, seq, GSI_CONTINUE_LINKING);
+
+  /* If there was a statement to move and the result of the statement
+     is going to be used, move it to right before the original
+     conditional.  */
+  if (stmt_to_move
+      && (gimple_assign_lhs (stmt_to_move) == result
+         || !has_single_use (gimple_assign_lhs (stmt_to_move))))
     {
       if (dump_file && (dump_flags & TDF_DETAILS))
        {
@@ -1032,8 +1041,6 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
       gsi_move_before (&gsi1, &gsi);
       reset_flow_sensitive_info (gimple_assign_lhs (stmt_to_move));
     }
-  if (seq)
-    gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
 
   replace_phi_edge_with_variable (cond_bb, e1, phi, result);