[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

[Christopher Lamb]

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)>;

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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