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[PATCH] Improve overhead of tree-affine.c a bit


When working on PR63184 I noticed that tree-affine.c is still one of
the gimple_assign_rhs_to_tree callers and does so quite aggressively
for no good reason.  The following restricts it to the cases we
handle in tree_to_aff_combination, axing one unreachable case.
It also makes sure to cache expanded combinations with SSA names
as keys rather than a GENERIC conversion tree which isn't shared
anyways.

Bootstrapped and tested on x86_64-unknown-linux-gnu, object files
in gcc/ are the same patched/unpatched with the exception of
tree-affine.o.

Applied to trunk.

Richard.

2018-12-10  Richard Biener  <rguenther@suse.de>

	* tree-affine.c (tree_to_aff_combination): Remove unreachable
	MEM_REF case.
	(aff_combination_expand): Cache on SSA names, not possibly
	on conversion trees.  Avoid expanding cases we do not handle.

diff --git a/gcc/tree-affine.c b/gcc/tree-affine.c
index 96b479dfc4c..41c52ab468d 100644
--- a/gcc/tree-affine.c
+++ b/gcc/tree-affine.c
@@ -351,6 +351,7 @@ tree_to_aff_combination (tree expr, tree type, aff_tree *comb)
       return;
 
     case MEM_REF:
+      gcc_unreachable ();
       if (TREE_CODE (TREE_OPERAND (expr, 0)) == ADDR_EXPR)
 	tree_to_aff_combination (TREE_OPERAND (TREE_OPERAND (expr, 0), 0),
 				 type, comb);
@@ -721,21 +722,39 @@ aff_combination_expand (aff_tree *comb ATTRIBUTE_UNUSED,
       if (TREE_CODE_CLASS (code) == tcc_reference)
 	continue;
 
-      if (!*cache)
-	*cache = new hash_map<tree, name_expansion *>;
-      name_expansion **slot = &(*cache)->get_or_insert (e);
-      exp = *slot;
-
+      name_expansion **slot = NULL;
+      if (*cache)
+	slot = (*cache)->get (name);
+      exp = slot ? *slot : NULL;
       if (!exp)
 	{
+	  /* Only bother to handle cases tree_to_aff_combination will.  */
+	  switch (code)
+	    {
+	    case POINTER_PLUS_EXPR:
+	    case PLUS_EXPR:
+	    case MINUS_EXPR:
+	    case MULT_EXPR:
+	    case NEGATE_EXPR:
+	    case BIT_NOT_EXPR:
+	    CASE_CONVERT:
+	      rhs = gimple_assign_rhs_to_tree (def);
+	      break;
+	    case ADDR_EXPR:
+	    case INTEGER_CST:
+	    case POLY_INT_CST:
+	      rhs = gimple_assign_rhs1 (def);
+	      break;
+	    default:
+	      continue;
+	    }
+	  tree_to_aff_combination (rhs, TREE_TYPE (name), &current);
 	  exp = XNEW (struct name_expansion);
 	  exp->in_progress = 1;
-	  *slot = exp;
-	  rhs = gimple_assign_rhs_to_tree (def);
-	  if (e != name)
-	    rhs = fold_convert (type, rhs);
-
-	  tree_to_aff_combination_expand (rhs, comb->type, &current, cache);
+	  if (!*cache)
+	    *cache = new hash_map<tree, name_expansion *>;
+	  (*cache)->put (name, exp);
+	  aff_combination_expand (&current, cache);
 	  exp->expansion = current;
 	  exp->in_progress = 0;
 	}
@@ -746,6 +765,8 @@ aff_combination_expand (aff_tree *comb ATTRIBUTE_UNUSED,
 	  gcc_assert (!exp->in_progress);
 	  current = exp->expansion;
 	}
+      if (!useless_type_conversion_p (comb->type, current.type))
+	aff_combination_convert (&current, comb->type);
 
       /* Accumulate the new terms to TO_ADD, so that we do not modify
 	 COMB while traversing it; include the term -coef * E, to remove


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