[LLVMdev] Custom allocators for MachineBasicBlocks and STL containers

[Eli Bendersky]

Hello,

I was looking at how the memory for MachineBasicBlocks is managed and
something seems strange.

On one hand, a MachineFunction uses a recycling allocator to create and
destroy MBBs without costly heap allocation (the same is done for
MachineInstrs, MachineOperands, etc.).

On the other hand, each MBB also has a number of STL vectors within it. For
example, for Predecessors, Successors, Weights, LiveIns. Maintaining these
vectors involves heap allocation and they don't have custom allocators,
AFAICS.

Is there some magic I'm missing here, or does this make little sense?

Eli
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