Fix profile merging WRT speculative edges

[Markus Trippelsdorf]

On 2015.01.20 at 21:04 +0100, Jan Hubicka wrote:
> this patch fixes ICE in ipa_merge_profiles on speculative edges. 
> 
> Bootstrapped/regtested x86_64-linux, comitted. Also tested by Markus on
> Firefox build.

This needs one additional fix. See below.

> 	PR ipa/63576
> 	* ipa-utils.c (ipa_merge_profiles): Merge speculative edges.
> Index: ipa-utils.c
> ===================================================================
> --- ipa-utils.c	(revision 219871)
> +++ ipa-utils.c	(working copy)
> @@ -539,7 +539,7 @@ ipa_merge_profiles (struct cgraph_node *
>      }
>    if (match)
>      {
> -      struct cgraph_edge *e;
> +      struct cgraph_edge *e, *e2;
>        basic_block srcbb, dstbb;
>  
>        /* TODO: merge also statement histograms.  */
> @@ -562,19 +562,95 @@ ipa_merge_profiles (struct cgraph_node *
>        pop_cfun ();
>        for (e = dst->callees; e; e = e->next_callee)
>  	{
> -	  gcc_assert (!e->speculative);
> +	  if (e->speculative)
> +	    continue;
>  	  e->count = gimple_bb (e->call_stmt)->count;
>  	  e->frequency = compute_call_stmt_bb_frequency
>  			     (dst->decl,
>  			      gimple_bb (e->call_stmt));
>  	}
> -      for (e = dst->indirect_calls; e; e = e->next_callee)
> +      for (e = dst->indirect_calls, e2 = src->indirect_calls; e;
> +	   e2 = (e2 ? e2->next_callee : NULL), e = e->next_callee)
>  	{
> -	  gcc_assert (!e->speculative);
> -	  e->count = gimple_bb (e->call_stmt)->count;
> -	  e->frequency = compute_call_stmt_bb_frequency
> -			     (dst->decl,
> -			      gimple_bb (e->call_stmt));
> +	  gcov_type count = gimple_bb (e->call_stmt)->count;
> +	  int freq = compute_call_stmt_bb_frequency
> +			(dst->decl,
> +			 gimple_bb (e->call_stmt));
> +	  /* When call is speculative, we need to re-distribute probabilities
> +	     the same way as they was.  This is not really correct because
> +	     in the other copy the speculation may differ; but probably it
> +	     is not really worth the effort.  */
> +	  if (e->speculative)
> +	    {
> +	      cgraph_edge *direct, *indirect;
> +	      cgraph_edge *direct2 = NULL, *indirect2 = NULL;
> +	      ipa_ref *ref;
> +
> +	      e->speculative_call_info (direct, indirect, ref);
> +	      gcc_assert (e == indirect);
> +	      if (e2 && e2->speculative)
> +	        e2->speculative_call_info (direct2, indirect2, ref);
> +	      if (indirect->count || direct->count)
> +		{
> +		  /* We should mismatch earlier if there is no matching
> +		     indirect edge.  */
> +		  if (!e2)
> +		    {
> +		      if (dump_file)
> +		        fprintf (dump_file,
> +				 "Mismatch in merging indirect edges\n");
> +		    }
> +		  else if (!e2->speculative)
> +		    indirect->count += e2->count;
> +		  else if (e2->speculative)
> +		    {
> +		      if (DECL_ASSEMBLER_NAME (direct2->callee->decl)
> +			  != DECL_ASSEMBLER_NAME (direct->callee->decl))
> +			{
> +			  if (direct2->count >= direct->count)
> +			    {
> +			      direct->redirect_callee (direct2->callee);
> +			      indirect->count += indirect2->count
> +						 + direct->count;
> +			      direct->count = direct2->count;
> +			    }
> +			  else
> +			    indirect->count += indirect2->count + direct2->count;
> +			}
> +		      else
> +			{
> +			   direct->count += direct2->count;
> +			   indirect->count += indirect2->count;
> +			}
> +		    }
> +		  int  prob = RDIV (direct->count * REG_BR_PROB_BASE ,
> +				    direct->count + indirect->count);
> +		  direct->frequency = RDIV (freq * prob, REG_BR_PROB_BASE);
> +		  indirect->frequency = RDIV (freq * (REG_BR_PROB_BASE - prob),
> +					      REG_BR_PROB_BASE);
> +		}
> +	      else
> +		/* At the moment we should have only profile feedback based
> +		   speculations when merging.  */
> +		gcc_unreachable ();
> +	    }
> +	  else if (e2->speculative)

+         else if (e2 && e2->speculative)

Otherwise it will crash:

lto1: internal compiler error: Segmentation fault
0xa12f6f crash_signal
        ../../gcc/gcc/toplev.c:381
0x88b190 ipa_merge_profiles(cgraph_node*, cgraph_node*)
        ../../gcc/gcc/ipa-utils.c:637
0x603722 lto_cgraph_replace_node
        ../../gcc/gcc/lto/lto-symtab.c:124
0x604cf3 lto_symtab_merge_symbols_1
        ../../gcc/gcc/lto/lto-symtab.c:619
0x604cf3 lto_symtab_merge_symbols()
        ../../gcc/gcc/lto/lto-symtab.c:647
0x5fa52e read_cgraph_and_symbols
        ../../gcc/gcc/lto/lto.c:3109
0x5fa52e lto_main()
        ../../gcc/gcc/lto/lto.c:3436
Please submit a full bug report,
with preprocessed source if appropriate.

> +	    {
> +	      cgraph_edge *direct, *indirect;
> +	      ipa_ref *ref;
> +
> +	      e2->speculative_call_info (direct, indirect, ref);
> +	      e->count = count;
> +	      e->frequency = freq;
> +	      int prob = RDIV (direct->count * REG_BR_PROB_BASE, e->count);
> +	      e->make_speculative (direct->callee, direct->count,
> +				   RDIV (freq * prob, REG_BR_PROB_BASE));
> +	    }
> +	  else
> +	    {
> +	      e->count = count;
> +	      e->frequency = freq;
> +	    }
>  	}
>        src->release_body ();
>        inline_update_overall_summary (dst);
> 

-- 
Markus