[PATCH] fix pr30907, worse code produced when an address is forward propagated

[Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>]

fwprop has a mechanism to propagate addresses only after loop 
optimization passes.  This is because invariant addresses can be hoisted 
out of the loop, and in this case it would not be beneficial to put them 
back in the loop.  It was not needed in CSE because it did not cross 
basic block boundaries, while the forward propagation is more global in 
nature.

This mechanism is currently enabled only if loop unrolling is done. 
However, PR30907 has a testcase where, on dataflow branch, the mechanism 
is needed also when loops are not unrolled.

Now, why is this needed only on dataflow branch?  It turns out that the 
reason is that the df bug detailed in 
http://gcc.gnu.org/ml/gcc-patches/2007-02/msg01797.html (and related to 
PR30841), on mainline, is preventing fwprop from doing the pessimizing 
transformation.  Since this bug is fixed on dataflow branch, as of now 
the transformation is done only on the branch.

Hence, I propose this patch for mainline rather than for dataflow branch.

Bootstrapped/regtested i686-pc-linux-gnu, ok for mainline?

Paolo
2007-02-22  Paolo Bonzini  <bonzini@gnu.org>

	PR rtl-optimization/30907
	* fwprop.c (forward_propagate_into): Never propagate inside a loop.
	(fwprop_init): Always call loop_optimizer_initialize.
	(fwprop_done): Always call loop_optimizer_finalize.
	(fwprop): We always have loop info now.
	(gate_fwprop_addr): Remove.
	(pass_fwprop_addr): Use gate_fwprop as gate.

Index: gcc-test-df/peak-gcc-src/gcc/fwprop.c
===================================================================
--- gcc-test-df/peak-gcc-src/gcc/fwprop.c	(revision 122189)
+++ gcc-test-df/peak-gcc-src/gcc/fwprop.c	(working copy)
@@ -886,10 +887,8 @@ forward_propagate_into (struct df_ref *u
   if (DF_REF_IS_ARTIFICIAL (def))
     return;
 
-  /* Do not propagate loop invariant definitions inside the loop if
-     we are going to unroll.  */
-  if (current_loops
-      && DF_REF_BB (def)->loop_father != DF_REF_BB (use)->loop_father)
+  /* Do not propagate loop invariant definitions inside the loop.  */
+  if (DF_REF_BB (def)->loop_father != DF_REF_BB (use)->loop_father)
     return;
 
   /* Check if the use is still present in the insn!  */
@@ -924,8 +923,7 @@ fwprop_init (void)
      loops and be careful about them.  But we have to call flow_loops_find
      before df_analyze, because flow_loops_find may introduce new jump
      insns (sadly) if we are not working in cfglayout mode.  */
-  if (flag_rerun_cse_after_loop && (flag_unroll_loops || flag_peel_loops))
-    loop_optimizer_init (0);
+  loop_optimizer_init (0);
 
   /* Now set up the dataflow problem (we only want use-def chains) and
      put the dataflow solver to work.  */
@@ -939,8 +937,7 @@ fwprop_init (void)
 static void
 fwprop_done (void)
 {
-  if (flag_rerun_cse_after_loop && (flag_unroll_loops || flag_peel_loops))
-    loop_optimizer_finalize ();
+  loop_optimizer_finalize ();
 
   free_dominance_info (CDI_DOMINATORS);
   cleanup_cfg (0);
@@ -979,8 +976,7 @@ fwprop (void)
     {
       struct df_ref *use = DF_USES_GET (i);
       if (use)
-	if (!current_loops 
-	    || DF_REF_TYPE (use) == DF_REF_REG_USE
+	if (DF_REF_TYPE (use) == DF_REF_REG_USE
 	    || DF_REF_BB (use)->loop_father == NULL)
 	  forward_propagate_into (use);
     }
@@ -1007,13 +1003,6 @@ struct tree_opt_pass pass_rtl_fwprop =
   0                                     /* letter */
 };
 
-static bool
-gate_fwprop_addr (void)
-{
-  return optimize > 0 && flag_forward_propagate && flag_rerun_cse_after_loop
-  	 && (flag_unroll_loops || flag_peel_loops);
-}
-
 static unsigned int
 fwprop_addr (void)
 {
@@ -1041,7 +1030,7 @@ fwprop_addr (void)
 struct tree_opt_pass pass_rtl_fwprop_addr =
 {
   "fwprop2",                            /* name */
-  gate_fwprop_addr,			/* gate */   
+  gate_fwprop,				/* gate */   
   fwprop_addr,				/* execute */       
   NULL,                                 /* sub */
   NULL,                                 /* next */