[llvm-dev] Spare Register at one Machine Instruction

Matthias Braun via llvm-dev
Thu, 19 Jan 2017 19:55:08 -0000

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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