combine.c (nonzero_bits): For paradoxical subregs, take LOAD_EXTENDED_OP into account.

	* combine.c (nonzero_bits): For paradoxical subregs, take
	LOAD_EXTENDED_OP into account.

From-SVN: r19928

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5bdc793f91c9a930765243e6431d35ea7f16d671..077c913a85b3052732e9e02181e30455eb4761e9 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+Thu May 21 19:32:27 1998  J"orn Rennecke <amylaar@cygnus.co.uk>
+
+       * combine.c (nonzero_bits): For paradoxical subregs, take
+       LOAD_EXTENDED_OP into account.
+
 Thu May 21 11:51:15 1998  Dave Brolley  <brolley@cygnus.com>
 
        * configure.in (extra_c_objs): add prefix.o.

diff --git a/gcc/combine.c b/gcc/combine.c
index 68c084f047d87a3053328781fb9b5157a323cd59..14da483ccd11194c936f75db9ef6038797da77c1 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7693,15 +7693,23 @@ nonzero_bits (x, mode)
        {
          nonzero &= nonzero_bits (SUBREG_REG (x), mode);
 
-#ifndef WORD_REGISTER_OPERATIONS
-         /* On many CISC machines, accessing an object in a wider mode
-            causes the high-order bits to become undefined.  So they are
-            not known to be zero.  */
-         if (GET_MODE_SIZE (GET_MODE (x))
-             > GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
-           nonzero |= (GET_MODE_MASK (GET_MODE (x))
-                       & ~ GET_MODE_MASK (GET_MODE (SUBREG_REG (x))));
+#if defined (WORD_REGISTER_OPERATIONS) && defined (LOAD_EXTEND_OP)
+         /* If this is a typical RISC machine, we only have to worry
+            about the way loads are extended.  */
+         if (LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (x))) == SIGN_EXTEND
+             ? (nonzero
+                & (1L << (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))) - 1)))
+             : LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (x))) != ZERO_EXTEND)
 #endif
+           {
+             /* On many CISC machines, accessing an object in a wider mode
+                causes the high-order bits to become undefined.  So they are
+                not known to be zero.  */
+             if (GET_MODE_SIZE (GET_MODE (x))
+                 > GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
+               nonzero |= (GET_MODE_MASK (GET_MODE (x))
+                           & ~ GET_MODE_MASK (GET_MODE (SUBREG_REG (x))));
+           }
        }
       break;