flow.c (find_basic_blocks): Calc upper bound for extra nops in max_uids_for_flow.

        * flow.c (find_basic_blocks): Calc upper bound for extra nops in
        max_uids_for_flow.
        (find_basic_blocks_1): Add a nop to the end of a basic block when
        a trailing call insn does not have abnormal control flow.
        * gcse.c (pre_transpout): New variable.
        (alloc_pre_mem, free_pre_mem, dump_pre_data): Bookkeeping for it.
        (compute_pre_transpout): Calculate it.
        (compute_pre_ppinout): Use it to eliminate impossible placements
        due to abnormal control flow through calls.
        (compute_pre_data): Call compute_pre_transpout.

From-SVN: r22907

1 files changed, 54 insertions, 15 deletions

diff --git a/gcc/flow.c b/gcc/flow.c
index d602436..773aaf2 100644
--- a/gcc/flow.c
+++ b/gcc/flow.c
@@ -306,6 +306,7 @@ find_basic_blocks (f, nregs, file, live_reachable_p)
   register int i;
   rtx nonlocal_label_list = nonlocal_label_rtx_list ();
   int in_libcall_block = 0;
+  int extra_uids_for_flow = 0;
 
   /* Count the basic blocks.  Also find maximum insn uid value used.  */
 
@@ -318,7 +319,6 @@ find_basic_blocks (f, nregs, file, live_reachable_p)
 
     for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
       {
-
 	/* Track when we are inside in LIBCALL block.  */
 	if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
 	    && find_reg_note (insn, REG_LIBCALL, NULL_RTX))
@@ -327,13 +327,33 @@ find_basic_blocks (f, nregs, file, live_reachable_p)
 	code = GET_CODE (insn);
 	if (INSN_UID (insn) > max_uid_for_flow)
 	  max_uid_for_flow = INSN_UID (insn);
-	if (code == CODE_LABEL
-	    || (GET_RTX_CLASS (code) == 'i'
-		&& (prev_code == JUMP_INSN
-		    || (prev_code == CALL_INSN
-			&& (nonlocal_label_list != 0 || eh_region))
-		    || prev_code == BARRIER)))
+	if (code == CODE_LABEL)
 	  i++;
+	else if (GET_RTX_CLASS (code) == 'i')
+	  {
+	    if (prev_code == JUMP_INSN || prev_code == BARRIER)
+	      i++;
+	    else if (prev_code == CALL_INSN)
+	      {
+		if (nonlocal_label_list != 0 || eh_region)
+		  i++;
+		else
+		  {
+		    /* Else this call does not force a new block to be
+		       created.  However, it may still be the end of a basic
+		       block if it is followed by a CODE_LABEL or a BARRIER.
+
+		       To disambiguate calls which force new blocks to be
+		       created from those which just happen to be at the end
+		       of a block we insert nops during find_basic_blocks_1
+		       after calls which are the last insn in a block by
+		       chance.  We must account for such insns in
+		       max_uid_for_flow.  */
+
+		    extra_uids_for_flow++;
+		  }
+	      }
+	  }
 
 	/* We change the code of the CALL_INSN, so that it won't start a
 	   new block.  */
@@ -360,6 +380,7 @@ find_basic_blocks (f, nregs, file, live_reachable_p)
      These cases are rare, so we don't need too much space.  */
   max_uid_for_flow += max_uid_for_flow / 10;
 #endif
+  max_uid_for_flow += extra_uids_for_flow;
 
   /* Allocate some tables that last till end of compiling this function
      and some needed only in find_basic_blocks and life_analysis.  */
@@ -410,6 +431,7 @@ find_basic_blocks_1 (f, nonlocal_label_list, live_reachable_p)
   int depth, pass;
   int in_libcall_block = 0;
   int deleted_handler = 0;
+  int call_had_abnormal_edge = 0;
 
   pass = 1;
   active_eh_region = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
@@ -456,8 +478,7 @@ find_basic_blocks_1 (f, nonlocal_label_list, live_reachable_p)
       else if (code == CODE_LABEL
 	       || (GET_RTX_CLASS (code) == 'i'
 		   && (prev_code == JUMP_INSN
-		       || (prev_code == CALL_INSN
-			   && (nonlocal_label_list != 0 || eh_note))
+		       || (prev_code == CALL_INSN && call_had_abnormal_edge)
 		       || prev_code == BARRIER)))
 	{
 	  basic_block_head[++i] = insn;
@@ -466,12 +487,26 @@ find_basic_blocks_1 (f, nonlocal_label_list, live_reachable_p)
 
 	  if (code == CODE_LABEL)
 	    {
-		LABEL_REFS (insn) = insn;
-		/* Any label that cannot be deleted
-		   is considered to start a reachable block.  */
-		if (LABEL_PRESERVE_P (insn))
-		  block_live[i] = 1;
-	      }
+	      LABEL_REFS (insn) = insn;
+	      /* Any label that cannot be deleted
+		 is considered to start a reachable block.  */
+	      if (LABEL_PRESERVE_P (insn))
+		block_live[i] = 1;
+	    }
+
+	  /* If the previous insn was a call that did not create an
+	     abnormal edge, we want to add a nop so that the CALL_INSN
+	     itself is not at basic_block_end.  This allows us to easily
+	     distinguish between normal calls and those which create
+	     abnormal edges in the flow graph.  */
+
+	  if (i > 0 && !call_had_abnormal_edge
+	      && GET_CODE (basic_block_end[i-1]) == CALL_INSN)
+	    {
+	      rtx nop = gen_rtx_USE (VOIDmode, const0_rtx);
+	      nop = emit_insn_after (nop, basic_block_end[i-1]);
+	      basic_block_end[i-1] = nop;
+	    }
 	}
 
       else if (GET_RTX_CLASS (code) == 'i')
@@ -524,6 +559,10 @@ find_basic_blocks_1 (f, nonlocal_label_list, live_reachable_p)
       if (code == CALL_INSN && in_libcall_block)
 	code = INSN;
 
+      /* Record whether this call created an edge.  */
+      if (code == CALL_INSN)
+	call_had_abnormal_edge = (nonlocal_label_list != 0 || eh_note);
+
       if (code != NOTE)
 	prev_code = code;