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

3 files changed, 138 insertions, 25 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 74dab80..d7d8490 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+Thu Oct  8 01:25:22 1998  Richard Henderson  <rth@cygnus.com>
+
+	* 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.
+
 Wed Oct  7 21:40:24 1998  David S. Miller  <davem@pierdol.cobaltmicro.com>
 
 	* config/sparc/sol2-sld-64.h (ASM_CPU_SPEC): Fix typo.
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;
 
diff --git a/gcc/gcse.c b/gcc/gcse.c
index c77aa33..0732cb4 100644
--- a/gcc/gcse.c
+++ b/gcc/gcse.c
@@ -3888,6 +3888,11 @@ static sbitmap *pre_pavout;
 static sbitmap *pre_ppin;
 static sbitmap *pre_ppout;
 
+/* Nonzero for expressions that are transparent at the end of the block.
+   This is only zero for expressions killed by abnormal critical edge
+   created by a calls.  */
+static sbitmap *pre_transpout;
+
 /* Used while performing PRE to denote which insns are redundant.  */
 static sbitmap pre_redundant;
 
@@ -3910,6 +3915,8 @@ alloc_pre_mem (n_blocks, n_exprs)
   pre_pavout = sbitmap_vector_alloc (n_blocks, n_exprs);
   pre_ppin = sbitmap_vector_alloc (n_blocks, n_exprs);
   pre_ppout = sbitmap_vector_alloc (n_blocks, n_exprs);
+
+  pre_transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
 }
 
 /* Free vars used for PRE analysis.  */
@@ -3920,7 +3927,6 @@ free_pre_mem ()
   free (pre_transp);
   free (pre_comp);
   free (pre_antloc);
-
   free (pre_avin);
   free (pre_avout);
   free (pre_antin);
@@ -3930,6 +3936,7 @@ free_pre_mem ()
   free (pre_pavout);
   free (pre_ppin);
   free (pre_ppout);
+  free (pre_transpout);
 }
 
 /* Dump PRE data.  */
@@ -3962,6 +3969,9 @@ dump_pre_data (file)
 		       pre_ppin, n_basic_blocks);
   dump_sbitmap_vector (file, "PRE placement possible on outgoing", "BB",
 		       pre_ppout, n_basic_blocks);
+
+  dump_sbitmap_vector (file, "PRE transparent on outgoing", "BB",
+		       pre_transpout, n_basic_blocks);
 }
 
 /* Compute the local properties of each recorded expression.
@@ -4129,6 +4139,57 @@ compute_pre_pavinout ()
     fprintf (gcse_file, "partially avail expr computation: %d passes\n", passes);
 }
 
+/* Compute transparent outgoing information for each block.
+
+   An expression is transparent to an edge unless it is killed by
+   the edge itself.  This can only happen with abnormal control flow,
+   when the edge is traversed through a call.  This happens with
+   non-local labels and exceptions.
+
+   This would not be necessary if we split the edge.  While this is
+   normally impossible for abnormal critical edges, with some effort
+   it should be possible with exception handling, since we still have
+   control over which handler should be invoked.  But due to increased
+   EH table sizes, this may not be worthwhile.  */
+
+static void
+compute_pre_transpout ()
+{
+  int bb;
+
+  sbitmap_vector_ones (pre_transpout, n_basic_blocks);
+
+  for (bb = 0; bb < n_basic_blocks; ++bb)
+    {
+      int i;
+
+      /* Note that flow inserted a nop a the end of basic blocks that
+	 end in call instructions for reasons other than abnormal
+	 control flow.  */
+      if (GET_CODE (BLOCK_END (bb)) != CALL_INSN)
+	continue;
+
+      for (i = 0; i < expr_hash_table_size; i++)
+	{
+	  struct expr *expr;
+	  for (expr = expr_hash_table[i]; expr ; expr = expr->next_same_hash)
+	    if (GET_CODE (expr->expr) == MEM)
+	      {
+		rtx addr = XEXP (expr->expr, 0);
+
+		if (GET_CODE (addr) == SYMBOL_REF
+		    && CONSTANT_POOL_ADDRESS_P (addr))
+		  continue;
+		
+		/* ??? Optimally, we would use interprocedural alias
+		   analysis to determine if this mem is actually killed
+		   by this call.  */
+		RESET_BIT (pre_transpout[bb], expr->bitmap_index);
+	      }
+	}
+    }
+}   
+
 /* Compute "placement possible" information on entrance and exit of
    each block.
 
@@ -4209,11 +4270,12 @@ compute_pre_ppinout ()
       for (bb = 0; bb < n_basic_blocks - 1; bb++)
 	{
 	  sbitmap_ptr ppout = pre_ppout[bb]->elms;
+	  sbitmap_ptr transpout = pre_transpout[bb]->elms;
 
 	  for (i = 0; i < size; i++)
 	    {
 	      int_list_ptr succ;
-	      SBITMAP_ELT_TYPE tmp = -1L;
+	      SBITMAP_ELT_TYPE tmp = *transpout;
 
 	      for (succ = s_succs[bb]; succ != NULL; succ = succ->next)
 		{
@@ -4226,13 +4288,14 @@ compute_pre_ppinout ()
 		  ppin = pre_ppin[succ_bb]->elms + i;
 		  tmp &= *ppin;
 		}
+
 	      if (*ppout != tmp)
 		{
 		  changed = 1;
-		  *ppout++ = tmp;
+		  *ppout = tmp;
 		}
-	      else
-		ppout++;
+
+	      ppout++; transpout++;
 	    }
 	}
 
@@ -4252,6 +4315,7 @@ compute_pre_data ()
   compute_pre_avinout ();
   compute_pre_antinout ();
   compute_pre_pavinout ();
+  compute_pre_transpout ();
   compute_pre_ppinout ();
   if (gcse_file)
     fprintf (gcse_file, "\n");
@@ -4376,10 +4440,7 @@ pre_insert_insn (expr, bb)
     }
   /* Likewise if the last insn is a call, as will happen in the presence
      of exception handling.  */
-  /* ??? The flag_exceptions test is not exact.  We don't know if we are
-     actually in an eh region.  Fix flow to tell us this.  */
-  else if (GET_CODE (insn) == CALL_INSN
-	   && (current_function_has_nonlocal_label || flag_exceptions))
+  else if (GET_CODE (insn) == CALL_INSN)
     {
       HARD_REG_SET parm_regs;
       int nparm_regs;
@@ -4409,7 +4470,7 @@ pre_insert_insn (expr, bb)
 	  {
 	    int regno = REGNO (XEXP (XEXP (p, 0), 0));
 	    if (regno >= FIRST_PSEUDO_REGISTER)
-	      abort();
+	      abort ();
 	    SET_HARD_REG_BIT (parm_regs, regno);
 	    nparm_regs++;
 	  }