[LLVMdev] PHI Elimination in Register Allocation Pass

[Natanael Ramos]

Good Afternoon.

I am a Computer Science undergraduate student in Brazil and as completion
of course work, I am developing an register allocator, using the
infrastructure of the LLVM.

To accomplish this task, I have based my implementation in allocators
already implemented in LLVM. But a question came to me while I was
researching in books and articles of compiler theory and own documentation
of LLVM, I noticed an important step in the optimization phase, the
deconstruction of form SSA (*PHI Elimination*), from what I've read, this
step has great impact on the code generation and can be done before or
after the register allocation phase. And I intend to implement the
allocator registers using the resources of SSA representation, making this
step (*PHI Elimination*) vital for development.

Looking at the source code of allocators of LLVM, I see no explicit call of
PHI Elimination (*AU.addRequiredID (PHIEliminationID)*), my question is
whether if this step is called, occurs when and where such a call?

-- 
Natanael Ramos
Membro do corpo discente de Ciência da Computação pelo Instituto Federal de
Minas Gerais - Campus Formiga
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