skip debug stmts when assigning locus discriminators

c-c++-common/goacc/kernels-loop-g.c has been failing (compare-debug)
on i686-linux-gnu since r13-3172, because the implementation enabled
debug stmts to cause discriminators to be assigned differently, and
the discriminators are printed in the .gkd dumps that -fcompare-debug
compares.

This patch prevents debug stmts from affecting the discriminators in
nondebug stmts, but enables debug stmts to get discriminators just as
nondebug stmts would if their line numbers match.

I suppose we could arrange for discriminators to be omitted from the
-fcompare-debug dumps, but keeping discriminators in sync is probably
good to avoid other potential sources of divergence between debug and
nondebug.


for  gcc/ChangeLog

	* tree-cfg.cc (assign_discriminators): Handle debug stmts.

1 files changed, 16 insertions, 0 deletions

diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 40a6f2a..a30a2de 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -1214,6 +1214,22 @@ assign_discriminators (void)
 	{
 	  gimple *stmt = gsi_stmt (gsi);
 
+	  /* Don't allow debug stmts to affect discriminators, but
+	     allow them to take discriminators when they're on the
+	     same line as the preceding nondebug stmt.  */
+	  if (is_gimple_debug (stmt))
+	    {
+	      if (curr_locus != UNKNOWN_LOCATION
+		  && same_line_p (curr_locus, &curr_locus_e,
+				  gimple_location (stmt)))
+		{
+		  location_t loc = gimple_location (stmt);
+		  location_t dloc = location_with_discriminator (loc,
+								 curr_discr);
+		  gimple_set_location (stmt, dloc);
+		}
+	      continue;
+	    }
 	  if (curr_locus == UNKNOWN_LOCATION)
 	    {
 	      curr_locus = gimple_location (stmt);