This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[PATCH 4/4] optimize MD more by trimming it to live registers


This patch trims the MD results to live registers.  This is important
because call-clobbered registers have an artificial definition after
every call.  When a lot of call-clobbered registers are not used by
register allocation, this would cause very dense MD sets to occur.
I did not seek actual testcases, but even x86 may have up to 40
such registers in integer-only functions, when MMX/SSE/x87 registers
are all enabled.

I thought that maybe committing it separately would help with bisection,
just in case.

Bootstrapped/regtested with the other patches x86_64-pc-linux-gnu, ok?

Paolo

2009-06-07  Paolo Bonzini  <bonzini@gnu.org>

	* df-problems.c (df_set_seen, df_unset_seen): Delete.
	(df_rd_local_compute, df_md_local_compute): Inline them.

	(df_md_scratch): New.
	(df_md_alloc, df_md_free): Allocate/free it.
	(df_md_local_compute): Only include live registers in init.
	(df_md_transfer_function): Prune the in-set computed by
	the confluence function, and the gen-set too.

Index: gcc/df-problems.c
===================================================================
--- gcc/df-problems.c	(branch rebase-fwprop-md)
+++ gcc/df-problems.c	(working copy)
@@ -157,27 +157,6 @@ df_print_bb_index (basic_block bb, FILE 
   fprintf (file, ")\n");
 }
 
-
-
-/* Make sure that the seen_in_insn and seen_in_block sbitmaps are set
-   up correctly. */
-
-static void
-df_set_seen (void)
-{
-  seen_in_block = BITMAP_ALLOC (&df_bitmap_obstack);
-  seen_in_insn = BITMAP_ALLOC (&df_bitmap_obstack);
-}
-
-
-static void
-df_unset_seen (void)
-{
-  BITMAP_FREE (seen_in_block);
-  BITMAP_FREE (seen_in_insn);
-}
-
-
 
 /*----------------------------------------------------------------------------
    REACHING DEFINITIONS
@@ -487,7 +466,8 @@ df_rd_local_compute (bitmap all_blocks)
   bitmap sparse_invalidated = problem_data->sparse_invalidated_by_call;
   bitmap dense_invalidated = problem_data->dense_invalidated_by_call;
 
-  df_set_seen ();
+  seen_in_block = BITMAP_ALLOC (&df_bitmap_obstack);
+  seen_in_insn = BITMAP_ALLOC (&df_bitmap_obstack);
 
   df_maybe_reorganize_def_refs (DF_REF_ORDER_BY_REG);
 
@@ -506,7 +486,9 @@ df_rd_local_compute (bitmap all_blocks)
 			  DF_DEFS_BEGIN (regno), 
 			  DF_DEFS_COUNT (regno));
     }
-  df_unset_seen ();
+
+  BITMAP_FREE (seen_in_block);
+  BITMAP_FREE (seen_in_insn);
 }
 
 
@@ -3960,6 +3942,10 @@ df_simulate_finalize_forwards (basic_blo
    block.
    ---------------------------------------------------------------------------*/
 
+/* Scratch var used by transfer functions.  This is used to do md analysis
+   only for live registers.  */
+static bitmap df_md_scratch;
+
 /* Set basic block info.  */
 
 static void
@@ -4003,6 +3989,7 @@ df_md_alloc (bitmap all_blocks)
                                            sizeof (struct df_md_bb_info), 50);
 
   df_grow_bb_info (df_md);
+  df_md_scratch = BITMAP_ALLOC (NULL);
 
   EXECUTE_IF_SET_IN_BITMAP (all_blocks, 0, bb_index, bi)
     {
@@ -4157,14 +4144,14 @@ df_md_local_compute (bitmap all_blocks)
   basic_block bb;
   bitmap *frontiers;
 
-  df_set_seen ();
+  seen_in_insn = BITMAP_ALLOC (NULL);
 
   EXECUTE_IF_SET_IN_BITMAP (all_blocks, 0, bb_index, bi1)
     {
       df_md_bb_local_compute (bb_index);
     }
   
-  df_unset_seen ();
+  BITMAP_FREE (seen_in_insn);
 
   frontiers = XNEWVEC (bitmap, last_basic_block);
   FOR_ALL_BB (bb)
@@ -4178,8 +4165,10 @@ df_md_local_compute (bitmap all_blocks)
       bitmap kill = df_md_get_bb_info (bb_index)->kill;
       EXECUTE_IF_SET_IN_BITMAP (frontiers[bb_index], 0, df_bb_index, bi2)
 	{
+	  basic_block bb = BASIC_BLOCK (df_bb_index);
 	  if (bitmap_bit_p (all_blocks, df_bb_index))
-	    bitmap_ior_into (df_md_get_bb_info (df_bb_index)->init, kill);
+	    bitmap_ior_and_into (df_md_get_bb_info (df_bb_index)->init, kill,
+				 df_get_live_in (bb));
 	}
     }
 }
@@ -4205,13 +4194,24 @@ df_md_reset (bitmap all_blocks)
 static bool
 df_md_transfer_function (int bb_index)
 {
+  basic_block bb = BASIC_BLOCK (bb_index);
   struct df_md_bb_info *bb_info = df_md_get_bb_info (bb_index);
   bitmap in = bb_info->in;
   bitmap out = bb_info->out;
   bitmap gen = bb_info->gen;
   bitmap kill = bb_info->kill;
 
-  return bitmap_ior_and_compl (out, gen, in, kill);
+  /* We need to use a scratch set here so that the value returned from
+     this function invocation properly reflects if the sets changed in
+     a significant way; i.e. not just because the live set was anded
+     in.  */
+  bitmap_and (df_md_scratch, gen, df_get_live_out (bb));
+
+  /* Multiple definitions of a register are not relevant if it is not
+     used.  Thus we trim the result to the places where it is live.  */
+  bitmap_and_into (in, df_get_live_in (bb));
+
+  return bitmap_ior_and_compl (out, df_md_scratch, in, kill);
 }
 
 /* Initialize the solution bit vectors for problem.  */
@@ -4274,6 +4274,7 @@ df_md_free (void)
 	}
     }
 
+  BITMAP_FREE (df_md_scratch);
   free_alloc_pool (df_md->block_pool);
 
   df_md->block_info_size = 0;


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]