re PR rtl-optimization/42258 (redundant register move around mul instruction)

gcc/
	PR rtl-optimization/42258
	* ira-lives.c (check_and_make_def_conflict): Ignore conflict for a
	use that may match DEF.

testsuite/
	PR rtl-optimization/42258
	* gcc.target/arm/thumb1-mul-moves.c: New test.

From-SVN: r157581

gcc/ChangeLog

+2010-03-19  Bernd Schmidt  <bernd.schmidt@codesourcery.com>
+
+	PR rtl-optimization/42258
+	* ira-lives.c (check_and_make_def_conflict): Ignore conflict for a
+	use that may match DEF.
+
 2010-03-19  Michael Matz  <matz@suse.de>
 
 	PR c++/43116

gcc/ira-lives.c

@@ -499,6 +499,8 @@ check_and_make_def_conflict (int alt, int def, enum reg_class def_cl)
 
   for (use = 0; use < recog_data.n_operands; use++)
     {
+      int alt1;
+
       if (use == def || recog_data.operand_type[use] == OP_OUT)
 	continue;
 
@@ -507,6 +509,22 @@ check_and_make_def_conflict (int alt, int def, enum reg_class def_cl)
       else
 	use_cl = recog_op_alt[use][alt].cl;
 
+      /* If there's any alternative that allows USE to match DEF, do not
+	 record a conflict.  If that causes us to create an invalid
+	 instruction due to the earlyclobber, reload must fix it up.  */	 
+      for (alt1 = 0; alt1 < recog_data.n_alternatives; alt1++)
+	if (recog_op_alt[use][alt1].matches == def
+	    || (use < recog_data.n_operands - 1
+		&& recog_data.constraints[use][0] == '%'
+		&& recog_op_alt[use + 1][alt1].matches == def)
+	    || (use >= 1
+		&& recog_data.constraints[use - 1][0] == '%'
+		&& recog_op_alt[use - 1][alt1].matches == def))
+	  break;
+
+      if (alt1 < recog_data.n_alternatives)
+	continue;
+
       advance_p = check_and_make_def_use_conflict (dreg, def_cl, use,
 						   use_cl, advance_p);
 

gcc/testsuite/ChangeLog

+2010-03-19  Bernd Schmidt  <bernd.schmidt@codesourcery.com>
+
+	PR rtl-optimization/42258
+	* gcc.target/arm/thumb1-mul-moves.c: New test.
+	
 2010-03-19  Michael Matz  <matz@suse.de>
 
 	PR c++/43116

gcc/testsuite/gcc.target/arm/thumb1-mul-moves.c

+/* Check for unnecessary register moves.  */
+/* { dg-options "-mthumb -Os" }  */
+/* { dg-require-effective-target arm_thumb1_ok } */
+
+int f(int x)
+{
+  return x*42;
+}
+
+/* { dg-final { scan-assembler-not "mov\[\\t \]*r0," } } */
+