[PATCH] Add flag to control straight-line strength reduction

[William J. Schmidt]

I overlooked adding a pass-control flag for strength reduction, added
here.  I named it -ftree-slsr for consistency with other -ftree- flags,
but could change it to -fgimple-slsr if you prefer that for a pass named
gimple-ssa-...

Bootstrapped and tested on powerpc-unknown-linux-gnu with no new
regressions.  Ok for trunk?

Thanks,
Bill


2012-07-17  Bill Schmidt  <wschm...@linux.ibm.com>

        * opts.c (default_option): Make -ftree-slsr default at -O1 and above.
        * gimple-ssa-strength-reduction.c (gate_strength_reduction): Use
        flag_tree_slsr.
        * common.opt: Add -ftree-slsr with flag_tree_slsr.


Index: gcc/opts.c
===================================================================
--- gcc/opts.c  (revision 189574)
+++ gcc/opts.c  (working copy)
@@ -452,6 +452,7 @@ static const struct default_options default_option
     { OPT_LEVELS_1_PLUS, OPT_ftree_ch, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_fcombine_stack_adjustments, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_fcompare_elim, NULL, 1 },
+    { OPT_LEVELS_1_PLUS, OPT_ftree_slsr, NULL, 1 },
 
     /* -O2 optimizations.  */
     { OPT_LEVELS_2_PLUS, OPT_finline_small_functions, NULL, 1 },
Index: gcc/gimple-ssa-strength-reduction.c
===================================================================
--- gcc/gimple-ssa-strength-reduction.c (revision 189574)
+++ gcc/gimple-ssa-strength-reduction.c (working copy)
@@ -1501,7 +1501,7 @@ execute_strength_reduction (void)
 static bool
 gate_strength_reduction (void)
 {
-  return optimize > 0;
+  return flag_tree_slsr;
 }
 
 struct gimple_opt_pass pass_strength_reduction =
Index: gcc/common.opt
===================================================================
--- gcc/common.opt      (revision 189574)
+++ gcc/common.opt      (working copy)
@@ -2080,6 +2080,10 @@ ftree-sink
 Common Report Var(flag_tree_sink) Optimization
 Enable SSA code sinking on trees
 
+ftree-slsr
+Common Report Var(flag_tree_slsr) Optimization
+Perform straight-line strength reduction
+
 ftree-sra
 Common Report Var(flag_tree_sra) Optimization
 Perform scalar replacement of aggregates