re PR tree-optimization/36881 (Creating runtime relocations for code which does not need it)

	PR tree-optimization/36881
	* tree-switch-conversion.c (check_final_bb): For flag_pic, check
	that each value doesn't need runtime relocations, for !flag_pic
	check that each value is just a valid initializer constant.

	* gcc.dg/tree-ssa/pr36881.c: New test.

From-SVN: r141129

gcc/ChangeLog

+2008-10-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/36881
+	* tree-switch-conversion.c (check_final_bb): For flag_pic, check
+	that each value doesn't need runtime relocations, for !flag_pic
+	check that each value is just a valid initializer constant.
+
 2008-10-14  Richard Sandiford  <rdsandiford@googlemail.com>
 
 	* config/mips/mips.h (reg_class): Remove HI_AND_GR_REGS,

gcc/testsuite/ChangeLog

+2008-10-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/36881
+	* gcc.dg/tree-ssa/pr36881.c: New test.
+
 2008-10-14  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/37819

gcc/testsuite/gcc.dg/tree-ssa/pr36881.c

+/* PR tree-optimization/36881 */
+/* { dg-do compile { target fpic } } */
+/* { dg-options "-O2 -fpic -fdump-tree-switchconv-all" } */
+
+const char *foo (int i)
+{
+  const char *p;
+  switch (i)
+    {
+    case 0:
+    case 6: p = ""; break;
+    case 1:
+    case 7: p = "abc"; break;
+    case 2:
+    case 8: p = "def"; break;
+    default: p = "ghi"; break;
+    }
+  return p;
+}
+
+/* { dg-final { scan-assembler-not "CSWTCH" } } */
+/* { dg-final { scan-tree-dump "need runtime relocations" "switchconv" } } */
+/* { dg-final { cleanup-tree-dump "switchconv" } } */

gcc/tree-switch-conversion.c

@@ -296,12 +296,29 @@ check_final_bb (void)
 	{
 	  basic_block bb = gimple_phi_arg_edge (phi, i)->src;
 
-	  if ((bb == info.switch_bb
-	       || (single_pred_p (bb) && single_pred (bb) == info.switch_bb))
-	      && !is_gimple_ip_invariant (gimple_phi_arg_def (phi, i)))
+	  if (bb == info.switch_bb
+	      || (single_pred_p (bb) && single_pred (bb) == info.switch_bb))
 	    {
-	      info.reason = "   Non-invariant value from a case\n";
-	      return false; /* Non-invariant argument.  */
+	      tree reloc, val;
+
+	      val = gimple_phi_arg_def (phi, i);
+	      if (!is_gimple_ip_invariant (val))
+		{
+		  info.reason = "   Non-invariant value from a case\n";
+		  return false; /* Non-invariant argument.  */
+		}
+	      reloc = initializer_constant_valid_p (val, TREE_TYPE (val));
+	      if ((flag_pic && reloc != null_pointer_node)
+		  || (!flag_pic && reloc == NULL_TREE))
+		{
+		  if (reloc)
+		    info.reason
+		      = "   Value from a case would need runtime relocations\n";
+		  else
+		    info.reason
+		      = "   Value from a case is not a valid initializer\n";
+		  return false;
+		}
 	    }
 	}
     }