[PATCH, PR 55579] Make SRA keep candidated with only debug replacements

[Martin Jambor]

Hi,

the patch below fixes PR 55579 by not disqualifying a candidate
variable when it does not have any real replacements but has
ones for debug statements only.

analyze_access_subtree has to return the same value regardless of
MAY_HAVE_DEBUG_STMTS or we get debug comparison errors.  I also have a
patch that simply avoids disqualifying candidates with no replacements
which means we keep some information about it so that SRA can remove a
few more un-needed reads but I suppose that is stage1 material.

OK for trunk?

Thanks,

Martin


2013-01-03  Martin Jambor  <mjam...@suse.cz>

        PR debug/55579
        * tree-sra.c (analyze_access_subtree): Return true also after
        potentially creating a debug-only replacement.

testsuite/
        * gcc.dg/tree-ssa/pr55579.c: New test.

Index: src/gcc/testsuite/gcc.dg/tree-ssa/pr55579.c
===================================================================
--- /dev/null
+++ src/gcc/testsuite/gcc.dg/tree-ssa/pr55579.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -g -fdump-tree-esra" } */
+
+struct S { int a; char b; char c; short d; };
+
+int
+foo (int x)
+{
+  struct S s = { x + 1, x + 2, x + 3, x + 4 };
+  char *p = &s.c;
+  return x;
+}
+
+/* { dg-final { scan-tree-dump "Created a debug-only replacement for s" "esra" 
} } */
Index: src/gcc/tree-sra.c
===================================================================
--- src.orig/gcc/tree-sra.c
+++ src/gcc/tree-sra.c
@@ -2197,20 +2197,25 @@ analyze_access_subtree (struct access *r
     }
   else
     {
-      if (MAY_HAVE_DEBUG_STMTS && allow_replacements
+      if (allow_replacements
          && scalar && !root->first_child
          && (root->grp_scalar_write || root->grp_assignment_write))
        {
          gcc_checking_assert (!root->grp_scalar_read
                               && !root->grp_assignment_read);
-         root->grp_to_be_debug_replaced = 1;
-         if (dump_file && (dump_flags & TDF_DETAILS))
+         sth_created = true;
+         if (MAY_HAVE_DEBUG_STMTS)
            {
-             fprintf (dump_file, "Marking ");
-             print_generic_expr (dump_file, root->base, 0);
-             fprintf (dump_file, " offset: %u, size: %u ",
-                      (unsigned) root->offset, (unsigned) root->size);
-             fprintf (dump_file, " to be replaced with debug statements.\n");
+             root->grp_to_be_debug_replaced = 1;
+             if (dump_file && (dump_flags & TDF_DETAILS))
+               {
+                 fprintf (dump_file, "Marking ");
+                 print_generic_expr (dump_file, root->base, 0);
+                 fprintf (dump_file, " offset: %u, size: %u ",
+                          (unsigned) root->offset, (unsigned) root->size);
+                 fprintf (dump_file, " to be replaced with debug "
+                          "statements.\n");
+               }
            }
        }
 
@@ -2220,17 +2225,11 @@ analyze_access_subtree (struct access *r
        root->grp_total_scalarization = 0;
     }
 
-  if (sth_created
-      && (!hole || root->grp_total_scalarization))
-    {
-      root->grp_covered = 1;
-      return true;
-    }
-  if (root->grp_write || TREE_CODE (root->base) == PARM_DECL)
+  if (!hole || root->grp_total_scalarization)
+    root->grp_covered = 1;
+  else if (root->grp_write || TREE_CODE (root->base) == PARM_DECL)
     root->grp_unscalarized_data = 1; /* not covered and written to */
-  if (sth_created)
-    return true;
-  return false;
+  return sth_created;
 }
 
 /* Analyze all access trees linked by next_grp by the means of