Carrot abandoned this revision.
Carrot added a comment.
Thanks for the clarification, I will propose another patch for my purpose.
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https://reviews.llvm.org/D132531/new/
https://reviews.llvm.org/D132531
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efriedma added a comment.
> A reserved physical register doesn't mean it can't be used by
> compiler/linker, it just means it can't be used by register allocator, see
> the comments in TargetRegisterInfo::getReservedRegs().
The target feature to "reserve" a register is meant to be "don't use th
Carrot added a comment.
I want to reserve most of the physical registers, so only a small number of
registers can be used by register allocator. Then I can write small test cases
to simulate high register pressure situation, it will be much easier to test
and debug register allocation changes.
kristof.beyls added a comment.
See https://reviews.llvm.org/D56305 and https://reviews.llvm.org/D48580 for
previous related discussions.
I think it would be helpful to understand the use case for being able to
reserve x8, x16, x17 and x19 better.
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Carrot added a comment.
A reserved physical register doesn't mean it can't be used by compiler/linker,
it just means it can't be used by register allocator, see the comments in
TargetRegisterInfo::getReservedRegs(). The most common example is the stack
pointer. So when we reserve X8, X16, X17 a
kristof.beyls added a comment.
My understanding is that X8, X16, X17 and X19 cannot be reserved because the
code generator in places will make use of them.
For example, using X19 as a base register in some cases. X16 and X17 are
defined by the ABI to potentially be clobbered on function calls &
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Reserved phys
