[llvm-dev] Spare Register at one Machine Instruction

[Matthias Braun via llvm-dev]

There is also the LivePhysReg facility that I would recomment if you just want to query for a free register and do not need the full feature set of the RegisterScavenger.

- Matthias

> On Jan 19, 2017, at 5:50 AM, Nemanja Ivanovic via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> I believe what you're after is the register scavenger.
> It's in: include/llvm/CodeGen/RegisterScavenging.h
> Implementation: lib/CodeGen/RegisterScavenging.cpp
> 
> On Thu, Jan 19, 2017 at 1:36 PM, Hong Hu via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> Hi All,
> 
> Given a machine instruction, is it possible to tell which register(s) is still not in use? 
> 
> For example, given one instruction A, if the one follows it (say B) defines register rax, then I can tell rax should spare at instruction A. 
> 
> The purpose is to use the spare register to replace registers used by A, for instrumentation purpose.
> 
> Regards,
> Hu Hong
> 
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