Re: Pitfalls in interference graph ?

shafi <shafitvm@gmail.com> writes:


>> > Now for building the interference graph what other than register pairs
>> > is there any other issues that one has to look out for?
>>
>> - Calling conventions, i.e., caller-saves versus callee-saves
>> registers, parameter-transfer registers and registers used for
>> return address and stack/frame pointer.
>>
> parameter-transfer registers,return address registers and
> stack/frame registers and other instruction specific and fixed-
> function specific registers are handled by perpending and appending
> move instructions to the register usages.
> For caller/callee saved registers : A call instruction must cause all
> volatile (caller-saves) registers to
> interfere will all virtual register live at the call point.
> Is there anything else other than this ?


You must make sure that the registers used for parameter passing are
considered live at the time of the call. You can do this by adding
these registers to the list of registers that the call instruction
reads (though it is, in fact, the called function that does this).
Also, make sure that the register(s) used for returning the function
result is considered live at the return point. You can do this by
adding this as a register read by the return instruction.


Chapter 9 of my book "Basics of Compiler Design" (which you can
download for free from http://www.diku.dk/~torbenm/Basics) considers
function calls and how this interacts with register allocation (which
is, otherwise, covered in chapter 8).


Torben

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