[LLVMdev] Best location in code generation for insertion of instrumentation to measure stack depth?

[Andrew Ruef]

I investigated the MachineFunctionPass (that is runOnMachineFunction, I
believe). In my experimentation it didn't seem that the MachineFrameInfo was
populated (it consistently said that the stack depth was 0, for example). I
might have been doing something wrong?

On Fri, Jul 8, 2011 at 5:21 PM, John Criswell <criswell at illinois.edu> wrote:

>  On 7/8/11 4:09 PM, Andrew Ruef wrote:
>
> Hi list,
>
>  I am trying to implement the technique outlined in the following paper:
> http://www.cs.umd.edu/~mwh/papers/martin10ownership.html in LLVM. My
> approach so far involves the use of an IR level transform (via
> runOnFunction) to identify memory loads and stores. One thing I need to do
> (I am pretty sure I need to do it at least) is automatically mark each stack
> frame as "owned" by the current thread.
>
>  I'm not sure where the best place in the LLVM architecture to do this is.
> As I currently understand it, the concept of a stack frame appears pretty
> late in target code generation. I've hacked in a hook for this in
> X86FrameLowering.cpp in the emitPrologue and emitEpilogue methods.
>
>  Is there a cleaner way I can do this? Is there a way I can subclass the
> X86 code generator to "hook" those two methods and insert my
> instrumentation? Is there something I'm missing with runOnMachineFunction?
>
>
> I'm stepping beyond what I know a little bit, but have you looked at
> writing a MachineFunctionPass?  A student here at Illinois wrote a
> MachineFunctionPass to insert additional epilogue code into functions.
> Assuming that it's possible, putting your functionality into a
> MachineFunctionPass should be cleaner than modifying the code generator
> directly (MachineFunctionPass'es may even be load-able into llc).
>
> Check out the doxygen docs for MachineFunctionPass (
> http://llvm.org/doxygen/classllvm_1_1MachineFunctionPass.html),
> MachineFunction (http://llvm.org/doxygen/classllvm_1_1MachineFunction.html),
> and MachineFrameInfo (
> http://llvm.org/doxygen/classllvm_1_1MachineFrameInfo.html).
>
> -- John T.
>
>
>  Thank you,
>
>  Andrew
>
>
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>
>
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