On Wed, Feb 27, 2013 at 7:37 PM, Wei Mi wrote:
> What do you think?
I think you'll not be able to teach fold_rtx to perform the
transformation you want it to do without having SHIFT_COUNT_TRUNCATED
set for i386. I already tried it the other day, but GCC won't do the
truncation without knowing the insn is really a shift insn and
shift_truncation_mask returns something useful.
Ciao!
Steven
Index: cse.c
===================================================================
--- cse.c (revision 196182)
+++ cse.c (working copy)
@@ -3179,9 +3179,22 @@ fold_rtx (rtx x, rtx insn)
switch (GET_CODE (folded_arg))
{
+ case SUBREG:
+ /* If the SUBREG_REG comes in from an AND, and this is not a
+ paradoxical subreg, then try to fold the SUBREG. */
+ if (REG_P (SUBREG_REG (folded_arg))
+ && ! paradoxical_subreg_p (folded_arg))
+ {
+ rtx y = lookup_as_function (SUBREG_REG (folded_arg), AND);
+ if (y != 0)
+ y = simplify_gen_binary(AND, GET_MODE (folded_arg),
+ XEXP(y, 0), XEXP(y, 1));
+ if (y != 0)
+ folded_arg = y;
+ }
+ /* ... fall through ... */
case MEM:
case REG:
- case SUBREG:
const_arg = equiv_constant (folded_arg);
break;
