On Thu, Oct 13, 2011 at 10:01 AM, Paolo Bonzini <bonz...@gnu.org> wrote: > On 10/13/2011 06:35 PM, Richard Kenner wrote: >>> >>> It never calls make_extraction. There are several cases handled >>> for AND operation. But >>> >>> (and:DI (plus:DI (subreg:DI (mult:SI (reg/v:SI 85 [ i ]) >>> (const_int 4 [0x4])) 0) >>> (subreg:DI (reg:SI 106) 0)) >>> (const_int 4294967292 [0xfffffffc])) >>> >>> isn't one of them. >> >> Yes, clearly. Otherwise it would work! The correct fix for this problem >> is to make it to do that. That's where this needs to be fixed: in >> make_compound_operation. > > An and:DI is cheaper than a zero_extend:DI of an and:SI. So GCC is correct > in not doing this transformation. I think adding a case to > make_compound_operation that simply undoes the transformation (without > calling make_extraction) is fine if you guard it with if (in_code == MEM). >
We first expand zero_extend:DI address to and:DI and then try to restore zero_extend:DI. Why do we do this transformation to begin with? -- H.J.
