Do not imply -fweb with -fpeel-loops

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
enabling -fpeel-loops with -O3 and -Ofast had unexpected effect of enabling
-fweb and -frename-registers.  This patch drop -fweb from list of passes that
are implied by -fpeel-loops because it is no longer needed since we do peeling
at tree instead of RTL and the out-of-ssa pass cares about this.

I will look into rename registers separately. My understanding is that rename
registers is not really that specific for -funroll-loops or -fpeel-loops.
Loop unrolling may make it bit more useful because it increases expected basic
block size and thus enables scheduler to do more.

Rather it depends on target whether register renaming is win. On out of order targets
where scheduling is not that imprtant it does not seem to be worth the compile time
and code size effects, while on targets that depends on scheduling it does.
Tonight tests on x86 shows improvmeents in botan which I think are related to renaming
(because they also improved when Bern temporarily enabled it few days back),
measurable code size regression (which is probably fixable if we make rename-registers
to not increase instruction encoding size) and noticeable compile time slowdown
(not sure if it is from regrename itself that is quite easy pass or from the fact
that scheduler has more freedom and thus work harder).

On the other hand both SPECint and SPECfp improved by about 2% on Itanium and
code size reduced.  I think similar effect should happen on superscalar inorder
tarets with constant size of instruction encoding.

I would say we should handle -frename-registers same way as we do -fschedule-insns.
I.e. enable/disable it on target basis rather than budnle it to loop unrolling.
But that is for future patch.  I will commit this and propose patch making -fpeel-loops
independent of rename-registers next

Honza

Bootstrapped/regtested x86_64-linux, will commit it shortly.

	* loop-init.c (gate): Do not enale RTL loop unroller with -fpeel-loops.
	It no longer does that.
	* toplev.c (process_options): Do not enable flag_web with -fpeel-loops.
Index: loop-init.c
===================================================================
--- loop-init.c	(revision 236894)
+++ loop-init.c	(working copy)
@@ -560,7 +560,7 @@ public:
   /* opt_pass methods: */
   virtual bool gate (function *)
     {
-      return (flag_peel_loops || flag_unroll_loops || flag_unroll_all_loops);
+      return (flag_unroll_loops || flag_unroll_all_loops);
     }
 
   virtual unsigned int execute (function *);
Index: toplev.c
===================================================================
--- toplev.c	(revision 236894)
+++ toplev.c	(working copy)
@@ -1296,7 +1296,7 @@ process_options (void)
 
   /* web and rename-registers help when run after loop unrolling.  */
   if (flag_web == AUTODETECT_VALUE)
-    flag_web = flag_unroll_loops || flag_peel_loops;
+    flag_web = flag_unroll_loops;
 
   if (flag_rename_registers == AUTODETECT_VALUE)
     flag_rename_registers = flag_unroll_loops || flag_peel_loops;