[llvm-dev] Spare Register at one Machine Instruction

[Hong Hu via llvm-dev]

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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