re PR middle-end/37221 (Missed early loop-unroll optimization - causes 40% degradation on SPU)

2009-04-02  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/37221
	* tree-flow.h (degenerate_phi_result): Declare.
	* tree-ssa-dom.c (degenerate_phi_result): Export.
	* tree-scalar-evolution.c (analyze_initial_condition): If
	the initial condition is defined by a degenerate PHI node
	use the degenerate value.

	* gcc.c-torture/compile/20090331-1.c: New testcase.

From-SVN: r145439

gcc/ChangeLog

+2009-04-02  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/37221
+	* tree-flow.h (degenerate_phi_result): Declare.
+	* tree-ssa-dom.c (degenerate_phi_result): Export.
+	* tree-scalar-evolution.c (analyze_initial_condition): If
+	the initial condition is defined by a degenerate PHI node
+	use the degenerate value.
+
 2009-04-01  Eric Botcazou  <ebotcazou@adacore.com>
 
 	PR rtl-optimization/39588

gcc/testsuite/ChangeLog

+2009-04-02  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/37221
+	* gcc.c-torture/compile/20090331-1.c: New testcase.
+
 2009-04-01  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gcc.c-torture/compile/20090401-1.c: New test.

gcc/testsuite/gcc.c-torture/compile/20090331-1.c

+struct re_pattern_buffer {
+    unsigned char *buffer;
+    unsigned long int allocated;
+};
+void byte_regex_compile (struct re_pattern_buffer *bufp,
+			 unsigned char *begalt, unsigned char *b)
+{
+  unsigned char *pfrom;
+  unsigned char *pto;
+
+  while ((unsigned long) (b - bufp->buffer + 3) > bufp->allocated)
+    {
+      unsigned char *old_buffer = bufp->buffer;
+      bufp->allocated <<= 1;
+      if (old_buffer != bufp->buffer)
+	{
+	  int incr = bufp->buffer - old_buffer;
+	  b += incr;
+	}
+    }
+  pfrom = b;
+  pto = b + 3;
+  while (pfrom != begalt)
+    *--pto = *--pfrom;
+}
+

gcc/tree-flow.h

@@ -919,6 +919,7 @@ bool simplify_stmt_using_ranges (gimple_stmt_iterator *);
 extern void dump_dominator_optimization_stats (FILE *);
 extern void debug_dominator_optimization_stats (void);
 int loop_depth_of_name (tree);
+tree degenerate_phi_result (gimple);
 
 /* In tree-ssa-copy.c  */
 extern void merge_alias_info (tree, tree);

gcc/tree-scalar-evolution.c

@@ -1577,6 +1577,20 @@ analyze_initial_condition (gimple loop_phi_node)
   if (init_cond == chrec_not_analyzed_yet)
     init_cond = chrec_dont_know;
 
+  /* During early loop unrolling we do not have fully constant propagated IL.
+     Handle degenerate PHIs here to not miss important unrollings.  */
+  if (TREE_CODE (init_cond) == SSA_NAME)
+    {
+      gimple def = SSA_NAME_DEF_STMT (init_cond);
+      tree res;
+      if (gimple_code (def) == GIMPLE_PHI
+	  && (res = degenerate_phi_result (def)) != NULL_TREE
+	  /* Only allow invariants here, otherwise we may break
+	     loop-closed SSA form.  */
+	  && is_gimple_min_invariant (res))
+	init_cond = res;
+    }
+
   if (dump_file && (dump_flags & TDF_DETAILS))
     {
       fprintf (dump_file, "  (init_cond = ");

gcc/tree-ssa-dom.c

@@ -2475,7 +2475,7 @@ avail_expr_eq (const void *p1, const void *p2)
 /* Given PHI, return its RHS if the PHI is a degenerate, otherwise return
    NULL.  */
 
-static tree
+tree
 degenerate_phi_result (gimple phi)
 {
   tree lhs = gimple_phi_result (phi);