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Re: Abt long long support
"Mohamed Shafi" <shafitvm@gmail.com> writes:
> So when i looked into the .md file i saw no patterns with DI machine
> mode ,used for long long(am i right?), execpt
>
> define_insn "adddi3" and define_insn "subdi3"
>
> The .md file says that this is to prevent gcc from synthesising it,
> though i didnt understand what that means.
If there is no adddi3 pattern, then gcc will handle 64-bit addition by
doing 32-bit additions, and similarly for 64-bit subtraction. Putting
an adddi3 pattern in the MD file lets the backend specify how to do
64-bit addition. The backend can do it more efficiently than the
generic approach if the target provides an add-with-carry instruction.
I don't see how we can say anything else useful since we don't know
anything about how your examples are failing to compile.
Ian