Hi!
While looking at PR50168, I've noticed that CLRSB isn't handled
in nonzero_bits1 (while FFS/POPCOUNT/PARITY/CLZ/CTZ are).
It means that combine can't optimize say clrsb insn followed by
zero or sign extension of the result.
Fixed thusly, ok for trunk?
2011-08-23 Jakub Jelinek <ja...@redhat.com>
* rtlanal.c (nonzero_bits1): Handle CLRSB.
--- gcc/rtlanal.c.jj 2011-08-22 08:17:07.000000000 +0200
+++ gcc/rtlanal.c 2011-08-23 19:46:13.000000000 +0200
@@ -1,7 +1,7 @@
/* Analyze RTL for GNU compiler.
Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
- 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
- Free Software Foundation, Inc.
+ 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
+ 2011 Free Software Foundation, Inc.
This file is part of GCC.
@@ -4273,6 +4273,11 @@ nonzero_bits1 (const_rtx x, enum machine
nonzero = -1;
break;
+ case CLRSB:
+ /* This is at most the number of bits in the mode minus 1. */
+ nonzero = ((unsigned HOST_WIDE_INT) 1 << (floor_log2 (mode_width))) - 1;
+ break;
+
case PARITY:
nonzero = 1;
break;
Jakub
