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[PATCH] Cleanup SCEV global state


This removes chrec_not_analyzed_yet, chrec_dont_know, and chrec_known
GC roots in favor of putting them in global_trees[] and hard-wire
chrec_not_analyzed_yet to NULL_TREE.

We don't stream any SCEV state so it's pointless to preload those
nodes.  It might possibly make sense to merge global_trees[]
and integer_types[] and split them again at the LTO-preload-nodes
boundary or even make the list of preloaded nodes opt-in
(and based on actual use statistics).

Bootstrap / regtest running on x86_64-unknown-linux-gnu.

Richard.

2019-07-02  Richard Biener  <rguenther@suse.de>

	* tree-core.h (enum tree_index): Add TI_CHREC_DONT_KNOW and
	TI_CHREC_KNOWN.
	* tree.h (chrec_not_analyzed_yet, chrec_dont_know, chrec_known):
	Define here.
	* tree.c (build_common_tree_nodes): Initialize them.
	* tree-chrec.h (chrec_not_analyzed_yet, chrec_dont_know, chrec_known):
	Make declarations comments.
	* tree-scalar-evolution.c (chrec_not_analyzed_yet, chrec_dont_know,
	chrec_known): Remove definitions.
	(initialize_scalar_evolutions_analyzer): Remove.
	(scev_initialize): Do not call initialize_scalar_evolutions_analyzer.
	* tree-streamer.c (preload_common_nodes): Do not preload
	TI_CHREC_DONT_KNOW or TI_CHREC_KNOWN.

Index: gcc/tree-core.h
===================================================================
--- gcc/tree-core.h	(revision 272742)
+++ gcc/tree-core.h	(working copy)
@@ -758,6 +758,9 @@ enum tree_index {
   TI_CURRENT_TARGET_PRAGMA,
   TI_CURRENT_OPTIMIZE_PRAGMA,
 
+  TI_CHREC_DONT_KNOW,
+  TI_CHREC_KNOWN,
+
   TI_MAX
 };
 
Index: gcc/tree.h
===================================================================
--- gcc/tree.h	(revision 272742)
+++ gcc/tree.h	(working copy)
@@ -4083,6 +4083,11 @@ tree_strip_any_location_wrapper (tree ex
 #define current_target_pragma		global_trees[TI_CURRENT_TARGET_PRAGMA]
 #define current_optimize_pragma		global_trees[TI_CURRENT_OPTIMIZE_PRAGMA]
 
+/* SCEV analyzer global shared trees.  */
+#define chrec_not_analyzed_yet		NULL_TREE
+#define chrec_dont_know			global_trees[TI_CHREC_DONT_KNOW]
+#define chrec_known			global_trees[TI_CHREC_KNOWN]
+
 #define char_type_node			integer_types[itk_char]
 #define signed_char_type_node		integer_types[itk_signed_char]
 #define unsigned_char_type_node		integer_types[itk_unsigned_char]
Index: gcc/tree.c
===================================================================
--- gcc/tree.c	(revision 272742)
+++ gcc/tree.c	(working copy)
@@ -10643,6 +10682,12 @@ build_common_tree_nodes (bool signed_cha
 
     va_list_type_node = t;
   }
+
+  /* SCEV analyzer global shared trees.  */
+  chrec_dont_know = make_node (SCEV_NOT_KNOWN);
+  TREE_TYPE (chrec_dont_know) = void_type_node;
+  chrec_known = make_node (SCEV_KNOWN);
+  TREE_TYPE (chrec_known) = void_type_node;
 }
 
 /* Modify DECL for given flags.
Index: gcc/tree-chrec.h
===================================================================
--- gcc/tree-chrec.h	(revision 272742)
+++ gcc/tree-chrec.h	(working copy)
@@ -23,11 +23,14 @@ along with GCC; see the file COPYING3.
 
 /* The following trees are unique elements.  Thus the comparison of another
    element to these elements should be done on the pointer to these trees,
-   and not on their value.  */
+   and not on their value.
 
-extern tree chrec_not_analyzed_yet;
-extern GTY(()) tree chrec_dont_know;
-extern GTY(()) tree chrec_known;
+   extern tree chrec_not_analyzed_yet;
+   extern tree chrec_dont_know;
+   extern tree chrec_known;
+
+   chrec_not_analyzed_yet is NULL_TREE and the others are defined
+   in global_trees[].  */
 
 /* After having added an automatically generated element, please
    include it in the following function.  */
Index: gcc/tree-scalar-evolution.c
===================================================================
--- gcc/tree-scalar-evolution.c	(revision 272742)
+++ gcc/tree-scalar-evolution.c	(working copy)
@@ -304,21 +304,6 @@ struct GTY((for_user)) scev_info_str {
 static unsigned nb_set_scev = 0;
 static unsigned nb_get_scev = 0;
 
-/* The following trees are unique elements.  Thus the comparison of
-   another element to these elements should be done on the pointer to
-   these trees, and not on their value.  */
-
-/* The SSA_NAMEs that are not yet analyzed are qualified with NULL_TREE.  */
-tree chrec_not_analyzed_yet;
-
-/* Reserved to the cases where the analyzer has detected an
-   undecidable property at compile time.  */
-tree chrec_dont_know;
-
-/* When the analyzer has detected that a property will never
-   happen, then it qualifies it with chrec_known.  */
-tree chrec_known;
-
 struct scev_info_hasher : ggc_ptr_hash<scev_info_str>
 {
   static hashval_t hash (scev_info_str *i);
@@ -3056,23 +3041,6 @@ gather_stats_on_scev_database (void)
 }
 
 
-
-/* Initializer.  */
-
-static void
-initialize_scalar_evolutions_analyzer (void)
-{
-  /* The elements below are unique.  */
-  if (chrec_dont_know == NULL_TREE)
-    {
-      chrec_not_analyzed_yet = NULL_TREE;
-      chrec_dont_know = make_node (SCEV_NOT_KNOWN);
-      chrec_known = make_node (SCEV_KNOWN);
-      TREE_TYPE (chrec_dont_know) = void_type_node;
-      TREE_TYPE (chrec_known) = void_type_node;
-    }
-}
-
 /* Initialize the analysis of scalar evolutions for LOOPS.  */
 
 void
@@ -3084,8 +3052,6 @@ scev_initialize (void)
 
   scalar_evolution_info = hash_table<scev_info_hasher>::create_ggc (100);
 
-  initialize_scalar_evolutions_analyzer ();
-
   FOR_EACH_LOOP (loop, 0)
     {
       loop->nb_iterations = NULL_TREE;
Index: gcc/tree-streamer.c
===================================================================
--- gcc/tree-streamer.c	(revision 272742)
+++ gcc/tree-streamer.c	(working copy)
@@ -377,6 +377,9 @@ preload_common_nodes (struct streamer_tr
 	&& i != TI_TARGET_OPTION_CURRENT
 	&& i != TI_CURRENT_TARGET_PRAGMA
 	&& i != TI_CURRENT_OPTIMIZE_PRAGMA
+	/* SCEV state shouldn't reach the IL.  */
+	&& i != TI_CHREC_DONT_KNOW
+	&& i != TI_CHREC_KNOWN
 	/* Skip va_list* related nodes if offloading.  For native LTO
 	   we want them to be merged for the stdarg pass, for offloading
 	   they might not be identical between host and offloading target.  */


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