fix for PR49888 var-tracking compile-time regression

[Alexandre Oliva <aoliva at redhat dot com>]

PR49888 introduced clobber_overlapping_mems to detach VALUEs (and
variables bound to them) from MEMs as the MEMs are modified.  This
turned out to be quite expensive, particularly the computation of
canonical addresses passed to alias dependency.

This patch introduces caching of the canonical addresses to alleviate
this expensive operation.  We cache mappings that apply to the entire
function, from equivalences recorded in the global cselib table, and
mappings that apply only to the local basic block.  This cut down 2% of
a full regstrap cycle, and about 1% of the time it took to build target
libraries for C, C++ and Java.

Regstrapped on x86_64-linux-gnu and i686-linux-gnu.  Ok to install?

Cache canonical addresses within VTA

From: Alexandre Oliva <aoliva@redhat.com>

for  gcc/ChangeLog

	PR debug/54114
	PR debug/54402
	PR debug/49888
	* var-tracking.c (negative_power_of_two_p): New.
	(global_get_addr_cache, local_get_addr_cache): New.
	(get_addr_from_global_cache, get_addr_from_local_cache): New.
	(vt_canonicalize_addr): Rewrite using the above.
	(local_get_addr_clear_given_value): New.
	(val_reset): Clear local cached entries.
	(compute_bb_dataflow): Create and release the local cache.
	(vt_emit_notes): Likewise.
	(vt_initialize, vt_finalize): Create and release the global
	cache, respectively.
---

 gcc/var-tracking.c |  243 +++++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 200 insertions(+), 43 deletions(-)


diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c
index 8c76fe0..befde0a 100644
--- a/gcc/var-tracking.c
+++ b/gcc/var-tracking.c
@@ -1948,6 +1948,14 @@ var_regno_delete (dataflow_set *set, int regno)
   *reg = NULL;
 }
 
+/* Return true if I is the negated value of a power of two.  */
+static bool
+negative_power_of_two_p (HOST_WIDE_INT i)
+{
+  unsigned HOST_WIDE_INT x = -(unsigned HOST_WIDE_INT)i;
+  return x == (x & -x);
+}
+
 /* Strip constant offsets and alignments off of LOC.  Return the base
    expression.  */
 
@@ -1958,12 +1966,123 @@ vt_get_canonicalize_base (rtx loc)
 	  || GET_CODE (loc) == AND)
 	 && GET_CODE (XEXP (loc, 1)) == CONST_INT
 	 && (GET_CODE (loc) != AND
-	     || INTVAL (XEXP (loc, 1)) < 0))
+	     || negative_power_of_two_p (INTVAL (XEXP (loc, 1)))))
     loc = XEXP (loc, 0);
 
   return loc;
 }
 
+/* This caches canonicalized addresses for VALUEs, computed using
+   information in the global cselib table.  */
+static struct pointer_map_t *global_get_addr_cache;
+
+/* This caches canonicalized addresses for VALUEs, computed using
+   information from the global cache and information pertaining to a
+   basic block being analyzed.  */
+static struct pointer_map_t *local_get_addr_cache;
+
+static rtx vt_canonicalize_addr (dataflow_set *, rtx);
+
+/* Return the canonical address for LOC, that must be a VALUE, using a
+   cached global equivalence or computing it and storing it in the
+   global cache.  */
+
+static rtx
+get_addr_from_global_cache (rtx const loc)
+{
+  rtx x;
+  void **slot;
+
+  gcc_checking_assert (GET_CODE (loc) == VALUE);
+  
+  slot = pointer_map_insert (global_get_addr_cache, loc);
+  if (*slot)
+    return (rtx)*slot;
+
+  x = canon_rtx (get_addr (loc));
+
+  /* Tentative, avoiding infinite recursion.  */
+  *slot = x;
+
+  if (x != loc)
+    {
+      rtx nx = vt_canonicalize_addr (NULL, x);
+      if (nx != x)
+	{
+	  /* The table may have moved during recursion, recompute
+	     SLOT.  */
+	  slot = pointer_map_contains (global_get_addr_cache, loc);
+	  *slot = x = nx;
+	}
+    }
+
+  return x;
+}
+
+/* Return the canonical address for LOC, that must be a VALUE, using a
+   cached local equivalence or computing it and storing it in the
+   local cache.  */
+
+static rtx
+get_addr_from_local_cache (dataflow_set *set, rtx const loc)
+{
+  rtx x;
+  void **slot;
+  decl_or_value dv;
+  variable var;
+  location_chain l;
+
+  gcc_checking_assert (GET_CODE (loc) == VALUE);
+  
+  slot = pointer_map_insert (local_get_addr_cache, loc);
+  if (*slot)
+    return (rtx)*slot;
+
+  x = get_addr_from_global_cache (loc);
+  
+  /* Tentative, avoiding infinite recursion.  */
+  *slot = x;
+
+  /* Recurse to cache local expansion of X, or if we need to search
+     for a VALUE in the expansion.  */
+  if (x != loc)
+    {
+      rtx nx = vt_canonicalize_addr (set, x);
+      if (nx != x)
+	{
+	  slot = pointer_map_contains (local_get_addr_cache, loc);
+	  *slot = x = nx;
+	}
+      return x;
+    }
+
+  dv = dv_from_rtx (x);
+  var = (variable) htab_find_with_hash (shared_hash_htab (set->vars),
+					dv, dv_htab_hash (dv));
+  if (!var)
+    return x;
+
+  /* Look for an improved equivalent expression.  */
+  for (l = var->var_part[0].loc_chain; l; l = l->next)
+    {
+      rtx base = vt_get_canonicalize_base (l->loc);
+      if (GET_CODE (base) == REG
+	  || (GET_CODE (base) == VALUE
+	      && canon_value_cmp (base, loc)))
+	{
+	  rtx nx = vt_canonicalize_addr (set, l->loc);
+	  if (x != nx)
+	    {
+	      slot = pointer_map_contains (local_get_addr_cache, loc);
+	      *slot = x = nx;
+	    }
+	  break;
+	}
+    }
+
+  return x;
+}
+
 /* Canonicalize LOC using equivalences from SET in addition to those
    in the cselib static table.  */
 
@@ -1972,69 +2091,56 @@ vt_canonicalize_addr (dataflow_set *set, rtx oloc)
 {
   HOST_WIDE_INT ofst = 0;
   enum machine_mode mode = GET_MODE (oloc);
-  rtx loc = canon_rtx (get_addr (oloc));
+  rtx loc = oloc;
+  rtx x;
+  bool retry = true;
 
-  /* Try to substitute a base VALUE for equivalent expressions as much
-     as possible.  The goal here is to expand stack-related addresses
-     to one of the stack base registers, so that we can compare
-     addresses for overlaps.  */
-  while (GET_CODE (vt_get_canonicalize_base (loc)) == VALUE)
+  while (retry)
     {
-      rtx x;
-      decl_or_value dv;
-      variable var;
-      location_chain l;
-
-      while (GET_CODE (loc) == PLUS)
+      while (GET_CODE (loc) == PLUS
+	     && GET_CODE (XEXP (loc, 1)) == CONST_INT)
 	{
 	  ofst += INTVAL (XEXP (loc, 1));
 	  loc = XEXP (loc, 0);
-	  continue;
 	}
 
       /* Alignment operations can't normally be combined, so just
 	 canonicalize the base and we're done.  We'll normally have
 	 only one stack alignment anyway.  */
-      if (GET_CODE (loc) == AND)
+      if (GET_CODE (loc) == AND
+	  && GET_CODE (XEXP (loc, 1)) == CONST_INT
+	  && negative_power_of_two_p (INTVAL (XEXP (loc, 1))))
 	{
 	  x = vt_canonicalize_addr (set, XEXP (loc, 0));
 	  if (x != XEXP (loc, 0))
 	    loc = gen_rtx_AND (mode, x, XEXP (loc, 1));
-	  loc = canon_rtx (get_addr (loc));
-	  break;
+	  retry = false;
 	}
 
-      x = canon_rtx (get_addr (loc));
-
-      /* We've made progress!  Start over.  */
-      if (x != loc || GET_CODE (x) != VALUE)
+      if (GET_CODE (loc) == VALUE)
 	{
-	  loc = x;
-	  continue;
-	}
-
-      dv = dv_from_rtx (x);
-      var = (variable) htab_find_with_hash (shared_hash_htab (set->vars),
-					    dv, dv_htab_hash (dv));
-      if (!var)
-	break;
+	  if (set)
+	    loc = get_addr_from_local_cache (set, loc);
+	  else
+	    loc = get_addr_from_global_cache (loc);
 
-      /* Look for an improved equivalent expression.  */
-      for (l = var->var_part[0].loc_chain; l; l = l->next)
-	{
-	  rtx base = vt_get_canonicalize_base (l->loc);
-	  if (GET_CODE (base) == REG
-	      || (GET_CODE (base) == VALUE
-		  && canon_value_cmp (base, loc)))
+	  /* Consolidate plus_constants.  */
+	  while (ofst && GET_CODE (loc) == PLUS
+		 && GET_CODE (XEXP (loc, 1)) == CONST_INT)
 	    {
-	      loc = l->loc;
-	      break;
+	      ofst += INTVAL (XEXP (loc, 1));
+	      loc = XEXP (loc, 0);
 	    }
-	}
 
-      /* No luck with the dataflow set, so we're done.  */
-      if (!l)
-	break;
+	  retry = false;
+	}
+      else
+	{
+	  x = canon_rtx (loc);
+	  if (retry)
+	    retry = (x != loc);
+	  loc = x;
+	}
     }
 
   /* Add OFST back in.  */
@@ -2358,6 +2464,17 @@ val_store (dataflow_set *set, rtx val, rtx loc, rtx insn, bool modified)
   val_bind (set, val, loc, modified);
 }
 
+/* Clear (canonical address) slots that reference X.  */
+
+static bool
+local_get_addr_clear_given_value (const void *v ATTRIBUTE_UNUSED,
+				  void **slot, void *x)
+{
+  if (vt_get_canonicalize_base ((rtx)*slot) == x)
+    *slot = NULL;
+  return true;
+}
+
 /* Reset this node, detaching all its equivalences.  Return the slot
    in the variable hash table that holds dv, if there is one.  */
 
@@ -2373,6 +2490,28 @@ val_reset (dataflow_set *set, decl_or_value dv)
 
   gcc_assert (var->n_var_parts == 1);
 
+  if (var->onepart == ONEPART_VALUE)
+    {
+      rtx x = dv_as_value (dv);
+      void **slot;
+      
+      /* Relationships in the global cache don't change, so reset the
+	 local cache entry only.  */
+      slot = pointer_map_contains (local_get_addr_cache, x);
+      if (slot)
+	{
+	  /* If the value resolved back to itself, odds are that other
+	     values may have cached it too.  These entries now refer
+	     to the old X, so detach them too.  Entries that used the
+	     old X but resolved to something else remain ok as long as
+	     that something else isn't also reset.  */
+	  if (*slot == x)
+	    pointer_map_traverse (local_get_addr_cache,
+				  local_get_addr_clear_given_value, x);
+	  *slot = NULL;
+	}
+    }
+
   cval = NULL;
   for (node = var->var_part[0].loc_chain; node; node = node->next)
     if (GET_CODE (node->loc) == VALUE
@@ -6420,6 +6559,9 @@ compute_bb_dataflow (basic_block bb)
   dataflow_set_copy (&old_out, out);
   dataflow_set_copy (out, in);
 
+  if (MAY_HAVE_DEBUG_INSNS)
+    local_get_addr_cache = pointer_map_create ();
+
   FOR_EACH_VEC_ELT (VTI (bb)->mos, i, mo)
     {
       rtx insn = mo->insn;
@@ -6696,6 +6838,9 @@ compute_bb_dataflow (basic_block bb)
 
   if (MAY_HAVE_DEBUG_INSNS)
     {
+      pointer_map_destroy (local_get_addr_cache);
+      local_get_addr_cache = NULL;
+
       dataflow_set_equiv_regs (out);
       htab_traverse (shared_hash_htab (out->vars), canonicalize_values_mark,
 		     out);
@@ -9236,9 +9381,16 @@ vt_emit_notes (void)
 	 subsequent basic blocks.  */
       emit_notes_for_differences (BB_HEAD (bb), &cur, &VTI (bb)->in);
 
+      if (MAY_HAVE_DEBUG_INSNS)
+	local_get_addr_cache = pointer_map_create ();
+
       /* Emit the notes for the changes in the basic block itself.  */
       emit_notes_in_bb (bb, &cur);
 
+      if (MAY_HAVE_DEBUG_INSNS)
+	pointer_map_destroy (local_get_addr_cache);
+      local_get_addr_cache = NULL;
+
       /* Free memory occupied by the in hash table, we won't need it
 	 again.  */
       dataflow_set_clear (&VTI (bb)->in);
@@ -9607,11 +9759,13 @@ vt_initialize (void)
       valvar_pool = create_alloc_pool ("small variable_def pool",
 				       sizeof (struct variable_def), 256);
       preserved_values.create (256);
+      global_get_addr_cache = pointer_map_create ();
     }
   else
     {
       scratch_regs = NULL;
       valvar_pool = NULL;
+      global_get_addr_cache = NULL;
     }
 
   if (MAY_HAVE_DEBUG_INSNS)
@@ -9948,6 +10102,9 @@ vt_finalize (void)
 
   if (MAY_HAVE_DEBUG_INSNS)
     {
+      if (global_get_addr_cache)
+	pointer_map_destroy (global_get_addr_cache);
+      global_get_addr_cache = NULL;
       if (loc_exp_dep_pool)
 	free_alloc_pool (loc_exp_dep_pool);
       loc_exp_dep_pool = NULL;


-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer