[RFA][PATCH] Use SCEV conditionally within vr-values and evrp range analysis

[Jeff Law <law@redhat.com>]

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Clients of the evrp range analysis may not have initialized the SCEV
infrastructure, and in fact my not want to (DOM for example).

Yet inside both vr-values.c and gimple-ssa-evrp-analyze.c we have calls
into SCEV (that will fault/abort if SCEV is not properly initialized).

This patch allows clients of vr-values.c and gimple-ssa-evrp-analyze.c
to indicate if they want SCEV analysis.

Bootstrapped and regression tested by itself as well as with the DOM
patches to use EVRP analysis  (which test the "don't want SCEV path).

OK for the trunk?

Jeff

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	* gimple-ssa-evrp-analyze.h (class evrp_range_analyzer): New data
	member USE_SCEV. 
	* gimple-ssa-evrp-analyze.c
	(evrp_range_analyzer::evrp_range_analyzer): Add new use_scev argument.
	Pass it to the vr_values ctor.
	(evrp_range_analyzer::record_ranges_from_phis): Conditionally use
	SCEV to refine ranges for PHIs.
	* gimple-ssa-evrp (evrp_dom_walker::evrp_dom_walker): Ask for
	SCEV analysis in the vr-values engine.
	* vr-values.h (class vr_values): New data meber USE_SCEV.
	* vr-values.c (vr_values::vr_values): Add new use_scev argument.
	(vr_values::extract_range_from_phi_node): Conditionally use
	SCEV to refine ranges for PHIs.
	

diff --git a/gcc/gimple-ssa-evrp-analyze.c b/gcc/gimple-ssa-evrp-analyze.c
index 68a2cdc..bc41be1 100644
--- a/gcc/gimple-ssa-evrp-analyze.c
+++ b/gcc/gimple-ssa-evrp-analyze.c
@@ -42,7 +42,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "vr-values.h"
 #include "gimple-ssa-evrp-analyze.h"
 
-evrp_range_analyzer::evrp_range_analyzer () : stack (10)
+evrp_range_analyzer::evrp_range_analyzer (bool use_scev_)
+  : vr_values (use_scev_), stack (10), use_scev (use_scev_)
 {
   edge e;
   edge_iterator ei;
@@ -176,7 +177,8 @@ evrp_range_analyzer::record_ranges_from_phis (basic_block bb)
 	     to use VARYING for them.  But we can still resort to
 	     SCEV for loop header PHIs.  */
 	  struct loop *l;
-	  if (interesting
+	  if (use_scev
+	      && interesting
 	      && (l = loop_containing_stmt (phi))
 	      && l->header == gimple_bb (phi))
 	  vr_values.adjust_range_with_scev (&vr_result, l, phi, lhs);
@@ -341,3 +343,4 @@ evrp_range_analyzer::pop_value_range (tree var)
   stack.pop ();
   return vr;
 }
+
diff --git a/gcc/gimple-ssa-evrp-analyze.h b/gcc/gimple-ssa-evrp-analyze.h
index 3d64c50..18f5b8c 100644
--- a/gcc/gimple-ssa-evrp-analyze.h
+++ b/gcc/gimple-ssa-evrp-analyze.h
@@ -23,7 +23,7 @@ along with GCC; see the file COPYING3.  If not see
 class evrp_range_analyzer
 {
  public:
-  evrp_range_analyzer (void);
+  evrp_range_analyzer (bool);
   ~evrp_range_analyzer (void) { stack.release (); }
 
   void enter (basic_block);
@@ -65,6 +65,9 @@ class evrp_range_analyzer
 
   /* STACK holds the old VR.  */
   auto_vec<std::pair <tree, value_range*> > stack;
+
+  /* Whether or not to use SCEV to refine ranges.  */
+  bool use_scev;
 };
 
 #endif /* GCC_GIMPLE_SSA_EVRP_ANALYZE_H */
diff --git a/gcc/gimple-ssa-evrp.c b/gcc/gimple-ssa-evrp.c
index f56d67f..13e4e16 100644
--- a/gcc/gimple-ssa-evrp.c
+++ b/gcc/gimple-ssa-evrp.c
@@ -69,6 +69,7 @@ class evrp_dom_walker : public dom_walker
 public:
   evrp_dom_walker ()
     : dom_walker (CDI_DOMINATORS),
+      evrp_range_analyzer (true),
       evrp_folder (evrp_range_analyzer.get_vr_values ())
     {
       need_eh_cleanup = BITMAP_ALLOC (NULL);
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 838822d..46be749 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -4737,6 +4737,7 @@ insert_range_assertions (void)
 class vrp_prop : public ssa_propagation_engine
 {
  public:
+  vrp_prop (bool use_scev_) : vr_values (use_scev_) { }
   enum ssa_prop_result visit_stmt (gimple *, edge *, tree *) FINAL OVERRIDE;
   enum ssa_prop_result visit_phi (gphi *) FINAL OVERRIDE;
 
@@ -6862,7 +6863,7 @@ execute_vrp (bool warn_array_bounds_p)
   /* For visiting PHI nodes we need EDGE_DFS_BACK computed.  */
   mark_dfs_back_edges ();
 
-  class vrp_prop vrp_prop;
+  class vrp_prop vrp_prop (true);
   vrp_prop.vrp_initialize ();
   vrp_prop.ssa_propagate ();
   vrp_prop.vrp_finalize (warn_array_bounds_p);
diff --git a/gcc/vr-values.c b/gcc/vr-values.c
index 2d11861..54b0be5 100644
--- a/gcc/vr-values.c
+++ b/gcc/vr-values.c
@@ -1907,7 +1907,8 @@ vr_values::dump_all_value_ranges (FILE *file)
 
 /* Initialize VRP lattice.  */
 
-vr_values::vr_values () : vrp_value_range_pool ("Tree VRP value ranges")
+vr_values::vr_values (bool use_scev_)
+  : vrp_value_range_pool ("Tree VRP value ranges"), use_scev (use_scev_)
 {
   values_propagated = false;
   num_vr_values = num_ssa_names;
@@ -2935,7 +2936,8 @@ scev_check:
      scev_check can be reached from two paths, one is a fall through from above
      "varying" label, the other is direct goto from code block which tries to
      avoid infinite simulation.  */
-  if ((l = loop_containing_stmt (phi))
+  if (use_scev
+      && (l = loop_containing_stmt (phi))
       && l->header == gimple_bb (phi))
     adjust_range_with_scev (vr_result, l, phi, lhs);
 
diff --git a/gcc/vr-values.h b/gcc/vr-values.h
index 124ee6f..bfeb1e4 100644
--- a/gcc/vr-values.h
+++ b/gcc/vr-values.h
@@ -37,7 +37,7 @@ along with GCC; see the file COPYING3.  If not see
 class vr_values
 {
  public:
-  vr_values (void);
+  vr_values (bool);
   ~vr_values (void);
 
   value_range *get_value_range (const_tree);
@@ -115,6 +115,9 @@ class vr_values
   /* Allocations for equivalences all come from this obstack.  */
   bitmap_obstack vrp_equiv_obstack;
 
+  /* Whether or not to use SCEV to refine ranges.  */
+  bool use_scev;
+
   /* Value range array.  After propagation, VR_VALUE[I] holds the range
      of values that SSA name N_I may take.  */
   unsigned int num_vr_values;