[llvm-commits] [llvm] r47658 - in /llvm/trunk: lib/Target/X86/README-X86-64.txt lib/Target/X86/X86Instr64bit.td test/CodeGen/X86/x86-64-and-mask.ll

[Chris Lattner]

On Mar 9, 2008, at 9:28 PM, Christopher Lamb wrote:

> I've prepared a change locally that allows you to write the following:
>
> // r & (2^32-1)
> def : Pat<(and GR64:$src, i64immFFFFFFFF),
>           (INSERT_SUBREG x86_impl_val_zero,
>             (MOV32rr (EXTRACT_SUBREG GR64:$src, x86_subreg_32bit)),
>             x86_subreg_32bit)>;

Woot, very nifty!  In td files, we generally use lower case for nodes,  
should 'INSERT_SUBREG' -> 'insert_subreg'?

-Chris

>
> On Mar 8, 2008, at 2:18 PM, Chris Lattner wrote:
>
>> One very simple and nice thing we could do is replace the  
>> duplicated instruction with a Pat pattern.  This would mean that  
>> there is only one instruction and the magic just happens in the  
>> isel.  This would give us something like this:
>>
>> def : Pat<(and GR64:$src, i64immFFFFFFFF),
>>           (x86_64_bit_part_of_32_bit
>>              (MOV32rr (subreg GR64:$src, x86_32bit_part_of_64bit)))>;
>>
>> This puts more pressure on the coalescer to coalesce away the  
>> copies, but seems like an overall better solution.  Is this the  
>> sort of thing you mean?
>
> --
> Christopher Lamb
>
>
>

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