llvm dev - Sep 2008 - [LLVMdev] Using VirtRegMap

I'm trying to piece together a few assignments for a graduate-level 
compilers class using LLVM; among these is a register allocator. I'd 
like to provide a register allocator that, given a partially-allocated 
VirtRegMap, will perform trivial register allocation (as in 
RegAllocSimple) on the remaining, unmapped virtual registers.

To make a long story short, I want to map a single virtual register to 
various physical registers at different times, keeping the relevant 
value in memory all along. Can VirtRegMap do this cleanly, or should I 
avoid this abstraction and issue stores and loads manually, through 
TargetInstrInfo?

Thanks,
- Matt Elder

On Sep 19, 2008, at 2:41 AM, Matt Elder wrote:
> I'm trying to piece together a few assignments for a graduate-level
> compilers class using LLVM; among these is a register allocator. I'd
> like to provide a register allocator that, given a partially-allocated
> VirtRegMap, will perform trivial register allocation (as in
> RegAllocSimple) on the remaining, unmapped virtual registers.
>
> To make a long story short, I want to map a single virtual register to
> various physical registers at different times, keeping the relevant
> value in memory all along. Can VirtRegMap do this cleanly, or should I
> avoid this abstraction and issue stores and loads manually, through
> TargetInstrInfo?
Please avoid using VirtRegMap. It's very tied to the current register  
allocation pieces and not easily reusable. One of my mission in life  
is to kill it.

Evan
>
>
> Thanks,
> - Matt Elder
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> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

On Friday 19 September 2008 11:37, Evan Cheng wrote:
> Please avoid using VirtRegMap. It's very tied to the current register
> allocation pieces and not easily reusable. One of my mission in life
> is to kill it.
Im surprised to see this.  I found it rather easy to re-use for custom
register allocators.

                                                -Dave