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[PATCH] reg_nonzero_bits valid use (take 2)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: rth at redhat dot com
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Sun, 9 Dec 2001 17:04:20 -0500
- Subject: [PATCH] reg_nonzero_bits valid use (take 2)
- References: <20011205125013.Z4087@devserv.devel.redhat.com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
For description of the problem please see
http://gcc.gnu.org/ml/gcc-patches/2001-12/msg00517.html
I just noticed that reg_nonzero_bits can be used even if
MODE is wider than GET_MODE(X), provided that bits outside of
X mode are set (we cannot tell anything about it).
Ok to commit?
2001-12-09 Jakub Jelinek <jakub@redhat.com>
* combine.c (nonzero_bits): If using reg_nonzero_bits,
we don't know anything about bits outside of X mode.
(num_sign_bit_copies): Likewise.
--- gcc/combine.c.jj Mon Nov 12 10:33:42 2001
+++ gcc/combine.c Sun Dec 9 23:58:12 2001
@@ -7965,7 +7965,14 @@ nonzero_bits (x, mode)
return nonzero_bits (tem, mode);
}
else if (nonzero_sign_valid && reg_nonzero_bits[REGNO (x)])
- return reg_nonzero_bits[REGNO (x)] & nonzero;
+ {
+ unsigned HOST_WIDE_INT mask = reg_nonzero_bits[REGNO (x)];
+
+ if (GET_MODE_BITSIZE (GET_MODE (x)) < mode_width)
+ /* We don't know anything about the upper bits. */
+ mask |= GET_MODE_MASK (mode) ^ GET_MODE_MASK (GET_MODE (x));
+ return nonzero & mask;
+ }
else
return nonzero;
@@ -8360,7 +8367,8 @@ num_sign_bit_copies (x, mode)
if (tem != 0)
return num_sign_bit_copies (tem, mode);
- if (nonzero_sign_valid && reg_sign_bit_copies[REGNO (x)] != 0)
+ if (nonzero_sign_valid && reg_sign_bit_copies[REGNO (x)] != 0
+ && GET_MODE_BITSIZE (GET_MODE (x)) == bitwidth)
return reg_sign_bit_copies[REGNO (x)];
break;
Jakub