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Instead of an std::vector<MachineOperand>, use MachineOperand arrays from an ArrayRecycler living in MachineFunction. This has several advantages: - MachineInstr now has a trivial destructor, making it possible to delete them in batches when destroying MachineFunction. This will be enabled in a later patch. - Bypassing malloc() and free() can be faster, depending on the system library. - MachineInstr objects and their operands are allocated from the same BumpPtrAllocator, so they will usually be next to each other in memory, providing better locality of reference. - Reduce MachineInstr footprint. A std::vector is 24 bytes, the new operand array representation only uses 8+4+1 bytes in MachineInstr. - Better control over operand array reallocations. In the old representation, the use-def chains would be reordered whenever a std::vector reached its capacity. The new implementation never changes the use-def chain order. Note that some decisions in the code generator depend on the use-def chain orders, so this patch may cause different assembly to be produced in a few cases. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171598 91177308-0d34-0410-b5e6-96231b3b80d8
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