llvm dev - Aug 2017 - alloca function in llvm

​Hi all,

I know that we use alloca method in llvm (llvmlite) to statically allocate a
stack slot for size values of type
typ. However, if I want to deallocate and free the memory from the allocated
stack, there is no free method. Does any one know how can I simply deallocate
the allocated stack in llvm or llvmlite?


Thank you in advance

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On 29 Aug 2017, at 17:30, Samaneh Berenjian via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> I know that we use alloca method in llvm (llvmlite) to statically allocate
a stack slot for size values of type typ. However, if I want to deallocate and
free the memory from the allocated stack, there is no free method. Does any one
know how can I simply deallocate the allocated stack in llvm or llvmlite?
I have no idea about llvmlite and any questions related to it are better
addressed to the llvmlite mailing list.

In LLVM, the alloca instruction allocates space in the current stack frame. 
This space is (as you would expect in any language with normal stack discipline)
freed automatically when the function returns.  If you have dynamic allocas that
are reached more than once in a function (for example, in a loop), then you can
use the stacksave and stackrestore intrinsics.  The stackrestore intrinsic will
reset the stack to a value from a corresponding stacksave, effectively freeing
all allocas that occur in the middle.  You cannot free individual allocas in any
other order (it would not make sense to do so, because they are stack
allocations).

David