With D134950, targets get notified when a virtual register is created and/or
cloned. Targets can do the needful with the delegate callback. AMDGPU propagates
the virtual register flags maintained in the target file itself. They are useful
to identify a certain type of machine operands while inserting spill stores and
reloads. Since RegAllocFast spills the physical register itself, there is no way
its virtual register can be mapped back to retrieve the flags. It can be solved
by passing the virtual register as an additional argument. This argument has no
use when the spill interfaces are called during the greedy allocator or even the
PrologEpilogInserter and can pass a null register in such cases.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D138656
In CSKYConstantIslands, when fix up an unconditional branch(CSKY::BR32) whose destination is
too far away to fit in its displacement field, and if the R15(LR) register has been
spilled in the prologue, then we can use BSR to implement a far jump. So we need estimate function
size, and spill R15(LR) when the function size >= unconditional branch(CSKY::BR32) can reach.
EstimateFunctionSizeInBytes function adds up all instructions and constant pool entries(each entry is 4 bytes).
Ooops. It constructs codegen infra and provide only basic code to generate first add instruction successfully.
Differential Revision: https://reviews.llvm.org/D112206
