PR target/18701

	* combine.c (combine_simplify_rtx): Do not allow paradoxical
	subregs of MEM.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@92762 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 81d0b99..86b5868 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,10 @@
 2004-12-31  Hans-Peter Nilsson  <hp@bitrange.com>
 
        PR target/18701
+       * combine.c (combine_simplify_rtx): Do not allow paradoxical
+       subregs of MEM.
+
+       PR target/18701
        * combine.c (gen_lowpart_for_combine): When stripping SUBREG of
        MEM, adjust imode and isize.
 

diff --git a/gcc/combine.c b/gcc/combine.c
index 61b93dd..90934e1 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -3983,10 +3983,14 @@ combine_simplify_rtx (rtx x, enum machine_mode op0_mode, int in_dest)
       }
 
       /* Don't change the mode of the MEM if that would change the meaning
-        of the address.  */
+        of the address.  Similarly, don't allow widening, as that may
+        access memory outside the defined object or using an address
+        that is invalid for a wider mode.  */
       if (MEM_P (SUBREG_REG (x))
          && (MEM_VOLATILE_P (SUBREG_REG (x))
-             || mode_dependent_address_p (XEXP (SUBREG_REG (x), 0))))
+             || mode_dependent_address_p (XEXP (SUBREG_REG (x), 0))
+             || (GET_MODE_SIZE (mode)
+                 > GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))))
        return gen_rtx_CLOBBER (mode, const0_rtx);
 
       /* Note that we cannot do any narrowing for non-constants since