On 03/02/2015 09:55 AM, Richard Henderson wrote:
> On 02/26/2015 05:46 PM, Aldy Hernandez wrote:
>> +;; Optimize division or modulo by constant power of 2, if the constant
>> +;; materializes only after expansion.
>> +(define_insn_and_split "*udivmod<mode>4_pow2"
>> + [(set (match_operand:SWI48 0 "register_operand" "=r")
>> + (udiv:SWI48 (match_operand:SWI48 2 "register_operand" "0")
>> + (match_operand:SWI48 3 "const_int_operand" "n")))
>> + (set (match_operand:SWI48 1 "register_operand" "=r")
>> + (umod:SWI48 (match_dup 2) (match_dup 3)))
>> + (clobber (reg:CC FLAGS_REG))]
>> + "UINTVAL (operands[3]) - 2 < <MODE_SIZE> * BITS_PER_UNIT
>> + && (UINTVAL (operands[3]) & (UINTVAL (operands[3]) - 1)) == 0"
>> + "#"
>> + "reload_completed"
>> + [(set (match_dup 1) (match_dup 2))
>> + (parallel [(set (match_dup 0) (lshiftrt:<MODE> (match_dup 2) (match_dup
>> 4)))
>> + (clobber (reg:CC FLAGS_REG))])
>> + (parallel [(set (match_dup 1) (and:<MODE> (match_dup 1) (match_dup 5)))
>> + (clobber (reg:CC FLAGS_REG))])]
>> +{
>
> Do you actually need the reload completed? Couldn't this be legitimately
> split
> before reload (and then parts of it DCE'd as necessary)?
>
> Otherwise, the split condition does need "&&" as mentioned by Uros.
Oh, I forgot -- even if you can exclude reload_completed,
you'd then need to use "&& 1" to effectively copy the first
condition.
r~
