re PR middle-end/70359 (Code size increase for x86/ARM/others compared to gcc-5.3.0)

2018-10-31  Richard Biener  <rguenther@suse.de>

	PR middle-end/70359
	PR middle-end/86270
	* tree-outof-ssa.c (insert_backedge_copies): Restrict
	copy generation to useful cases.  Place the copy before
	the definition of the backedge value when possible.

	* gcc.target/i386/pr70359.c: New testcase.
	* gcc.target/i386/pr86270.c: Likewise.

From-SVN: r265677

gcc/ChangeLog

+2018-10-31  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/70359
+	PR middle-end/86270
+	* tree-outof-ssa.c (insert_backedge_copies): Restrict
+	copy generation to useful cases.  Place the copy before
+	the definition of the backedge value when possible.
+
 2018-10-31  Claudiu Zissulescu  <claziss@synopsys.com>
 
 	* config/arc/arc-arch.h (ARC_TUNE_ARC7XX): New tune value.

gcc/testsuite/ChangeLog

+2018-10-31  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/70359
+	PR middle-end/86270
+	* gcc.target/i386/pr70359.c: New testcase.
+	* gcc.target/i386/pr86270.c: Likewise.
+
 2018-10-31  Claudiu Zissulescu  <claziss@synopsys.com>
 
 	* gcc.target/arc/jumptable.c: New test.

gcc/testsuite/gcc.target/i386/pr70359.c

+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+char* inttostr(int i, char* buf, int len)
+{
+  unsigned int ui = (i > 0) ? i : -i;
+  char *p = buf + len - 1;
+  *p = '\0';
+  do {
+    *--p = '0' + (ui % 10);
+  } while ((ui /= 10) != 0);
+  if (i < 0) {
+    *--p = '-';
+  }
+  return p;
+}
+
+/* In out-of-SSA we should have avoided splitting the latch edge of the
+   loop by inserting copies.  */
+/* { dg-final { scan-assembler-times "L\[0-9\]+:" 2 } } */

gcc/testsuite/gcc.target/i386/pr86270.c

+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int *a;
+long len;
+
+int
+test ()
+{
+  for (int i = 0; i < len + 1; i++)
+    a[i]=i;
+}
+
+/* Check we do not split the backedge but keep nice loop form.  */
+/* { dg-final { scan-assembler-times "L\[0-9\]+:" 2 } } */

gcc/tree-outof-ssa.c

@@ -1171,15 +1171,19 @@ insert_backedge_copies (void)
 	    {
 	      tree arg = gimple_phi_arg_def (phi, i);
 	      edge e = gimple_phi_arg_edge (phi, i);
+	      /* We are only interested in copies emitted on critical
+                 backedges.  */
+	      if (!(e->flags & EDGE_DFS_BACK)
+		  || !EDGE_CRITICAL_P (e))
+		continue;
 
 	      /* If the argument is not an SSA_NAME, then we will need a
-		 constant initialization.  If the argument is an SSA_NAME with
-		 a different underlying variable then a copy statement will be
-		 needed.  */
-	      if ((e->flags & EDGE_DFS_BACK)
-		  && (TREE_CODE (arg) != SSA_NAME
-		      || SSA_NAME_VAR (arg) != SSA_NAME_VAR (result)
-		      || trivially_conflicts_p (bb, result, arg)))
+		 constant initialization.  If the argument is an SSA_NAME then
+		 a copy statement may be needed.  First handle the case
+		 where we cannot insert before the argument definition.  */
+	      if (TREE_CODE (arg) != SSA_NAME
+		  || (gimple_code (SSA_NAME_DEF_STMT (arg)) == GIMPLE_PHI
+		      && trivially_conflicts_p (bb, result, arg)))
 		{
 		  tree name;
 		  gassign *stmt;
@@ -1226,6 +1230,34 @@ insert_backedge_copies (void)
 		    gsi_insert_after (&gsi2, stmt, GSI_NEW_STMT);
 		  SET_PHI_ARG_DEF (phi, i, name);
 		}
+	      /* Insert a copy before the definition of the backedge value
+		 and adjust all conflicting uses.  */
+	      else if (trivially_conflicts_p (bb, result, arg))
+		{
+		  gimple *def = SSA_NAME_DEF_STMT (arg);
+		  if (gimple_nop_p (def)
+		      || gimple_code (def) == GIMPLE_PHI)
+		    continue;
+		  tree name = copy_ssa_name (result);
+		  gimple *stmt = gimple_build_assign (name, result);
+		  imm_use_iterator imm_iter;
+		  gimple *use_stmt;
+		  /* The following matches trivially_conflicts_p.  */
+		  FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, result)
+		    {
+		      if (gimple_bb (use_stmt) != bb
+			  || (gimple_code (use_stmt) != GIMPLE_PHI
+			      && (maybe_renumber_stmts_bb (bb), true)
+			      && gimple_uid (use_stmt) > gimple_uid (def)))
+			{
+			  use_operand_p use;
+			  FOR_EACH_IMM_USE_ON_STMT (use, imm_iter)
+			    SET_USE (use, name);
+			}
+		    }
+		  gimple_stmt_iterator gsi = gsi_for_stmt (def);
+		  gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
+		}
 	    }
 	}