[llvm-dev] Reserve registers not to be used by the compiler

Rail Shafigulin via llvm-dev llvm-dev at lists.llvm.org
Mon Dec 21 16:40:00 PST 2015

Does anyone know if there is a way to reserve a register set not to be used
by a compiler? For example there are 64 available registers and the
compiler can use only registers 0-31 and 40-45, and the others should be
left alone.

I know that the simplest solution is to simply change number registers in
one of the .td files, but what I'm looking is an option to use at run time.
I need this to research various register combinations. Recompiling and
running tests takes some time. If I could compile my code with say 128
registers and thn tell compiler to use only a certain set (say 0-32) at run
time then this would significantly speed up my testing. I would be able to
see what the code is doing for the same test with a 32 registers vs 64 vs
96 vs any number up to 128.

Does anyone know if there is a way to do it? Any help is appreciated.

Rail Shafigulin
Software Engineer
Esencia Technologies
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