[llvm-commits] [llvm] r78318 - in /llvm/trunk: include/llvm/CodeGen/RegisterScavenging.h lib/CodeGen/RegisterScavenging.cpp

[John Mosby]

On Thu, Aug 6, 2009 at 2:41 PM, Jakob Stoklund Olesen <stoklund at 2pi.dk>wrote:

>
> The RS can get you a register in two ways:
>
> 1. FindUnusedReg() tries to find a register that is currently not
> being used, and so can be used _for free_.
> 2. scavengeRegister() will create a free register by saving it to the
> emergency spill slot.


Indeed.


> FindUnusedReg() must not return a CSR that has not been spilled yet -
> it won't be spilled at all if that happens. It will simply be clobbered.


We're changing PEI to allow it to allocate registers using RS in
certain situations. It will use CSRs that are not already used in the
function and spill them as necessary.
I'm going to disable part of my last commit until I have finished the
changes to PEI.

Thanks!
John
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