re PR target/27855 (reassociation causes the RA to be confused)

        PR target/27855
        * doc/extend.texi: Add ftree-reassoc flag.
        * common.opt (ftree-reassoc): New flag.
        * tree-ssa-reassoc.c (gate_tree_ssa_reassoc): New static function.
        (struct tree_opt_pass pass_reassoc): Use gate_tree_ssa_reassoc.

From-SVN: r126491

gcc/ChangeLog

 2007-07-09  Uros Bizjak  <ubizjak@gmail.com>
 
+	PR target/27855
+	* doc/invoke.texi: Add ftree-reassoc flag.
+	* common.opt (ftree-reassoc): New flag.
+	* tree-ssa-reassoc.c (gate_tree_ssa_reassoc): New static function.
+	(struct tree_opt_pass pass_reassoc): Use gate_tree_ssa_reassoc.
+
+2007-07-09  Uros Bizjak  <ubizjak@gmail.com>
+
 	PR tree-optimization/32681
 	* tree-if-conv.c (find_phi_replacement_condition): Use the condition
 	saved in second_edge->aux when first_bb is a loop header.
@@ -2848,7 +2856,7 @@
 2007-06-08  Harsha Jagasia <harsha.jagasia@amd.com>
 	    Tony Linthicum <tony.linthicum@amd.com>
 
-	* doc/extend.texi: Add fvect-cost-model flag.
+	* doc/invoke.texi: Add fvect-cost-model flag.
 	* common.opt (fvect-cost-model): New flag.
 	* tree-vectorizer.c (new_stmt_vec_info): Initialize inside and outside
 	cost fields in stmt_vec_info struct for STMT.

gcc/common.opt

@@ -1063,6 +1063,10 @@ ftree-pre
 Common Report Var(flag_tree_pre) Optimization
 Enable SSA-PRE optimization on trees
 
+ftree-reassoc
+Common Report Var(flag_tree_reassoc) Init(1) Optimization
+Enable reassociation on tree level
+
 ftree-salias
 Common Report Var(flag_tree_salias) Optimization
 Perform structural alias analysis

gcc/doc/invoke.texi

@@ -353,7 +353,7 @@ Objective-C and Objective-C++ Dialects}.
 -fstrict-aliasing  -fstrict-overflow  -ftracer  -fthread-jumps @gol
 -funroll-all-loops  -funroll-loops  -fpeel-loops @gol
 -fsplit-ivs-in-unroller -funswitch-loops @gol
--fvariable-expansion-in-unroller @gol
+-fvariable-expansion-in-unroller -ftree-reassoc @gol
 -ftree-pre  -ftree-ccp  -ftree-dce -ftree-loop-optimize @gol
 -ftree-loop-linear -ftree-loop-im -ftree-loop-ivcanon -fivopts @gol
 -fcheck-data-deps @gol
@@ -5584,9 +5584,9 @@ ones to optimal placement using LCM.
 
 @item -freschedule-modulo-scheduled-loops
 @opindex fscheduling-in-modulo-scheduled-loops
-The modulo scheduling comes before the traditional scheduling, if a loop was modulo scheduled
-we may want to prevent the later scheduling passes from changing its schedule, we use this
-option to control that.
+The modulo scheduling comes before the traditional scheduling, if a loop
+was modulo scheduled we may want to prevent the later scheduling passes
+from changing its schedule, we use this option to control that.
 
 @item -fcaller-saves
 @opindex fcaller-saves
@@ -5600,6 +5600,10 @@ those which have no call-preserved registers to use instead.
 
 Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
 
+@item -ftree-reassoc
+Perform Reassociation on trees  This flag is enabled by default
+at @option{-O} and higher.
+
 @item -ftree-pre
 Perform Partial Redundancy Elimination (PRE) on trees.  This flag is
 enabled by default at @option{-O2} and @option{-O3}.

gcc/tree-ssa-reassoc.c

@@ -1476,15 +1476,21 @@ execute_reassoc (void)
   return 0;
 }
 
+static bool
+gate_tree_ssa_reassoc (void)
+{
+  return flag_tree_reassoc != 0;
+}
+
 struct tree_opt_pass pass_reassoc =
 {
   "reassoc",				/* name */
-  NULL,				/* gate */
-  execute_reassoc,				/* execute */
+  gate_tree_ssa_reassoc,		/* gate */
+  execute_reassoc,			/* execute */
   NULL,					/* sub */
   NULL,					/* next */
   0,					/* static_pass_number */
-  TV_TREE_REASSOC,				/* tv_id */
+  TV_TREE_REASSOC,			/* tv_id */
   PROP_cfg | PROP_ssa | PROP_alias,	/* properties_required */
   0,					/* properties_provided */
   0,					/* properties_destroyed */