[Bug target/55876] internal compiler error: in gen_rtx_SUBREG, at emit-rtl.c:776

[vries at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55876



--- Comment #2 from vries at gcc dot gnu.org 2013-01-04 16:00:07 UTC ---

This patch introduces an assert that triggers before rather than during

gen_rtx_SUBREG:

...

Index: optabs.c

===================================================================

--- optabs.c (revision 194898)

+++ optabs.c (working copy)

@@ -330,7 +330,12 @@ widen_operand (rtx op, enum machine_mode

   /* If MODE is no wider than a single word, we return a paradoxical

      SUBREG.  */

   if (GET_MODE_SIZE (mode) <= UNITS_PER_WORD)

-    return gen_rtx_SUBREG (mode, force_reg (GET_MODE (op), op), 0);

+    {

+      /* Check that the result is a paradoxical subreg (outer mode strictly

+        larger than inner mode.  */

+      gcc_assert (GET_MODE_SIZE (mode) > GET_MODE_SIZE (GET_MODE (op)));

+      return gen_rtx_SUBREG (mode, force_reg (GET_MODE (op), op), 0);

+    }



   /* Otherwise, get an object of MODE, clobber it, and set the low-order

      part to OP.  */

...



This assert allows triggers both with -EB and -EL, while the original assert

only triggers with -EB.