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Re: PATCH: PR rtl-optimization/50696: [x32] Unnecessary lea

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).

Paolo

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