[llvm-dev] Unify debug and optimized variable locations with llvm.dbg.addr [was: DW_OP_LLVM_memory]

[Reid Kleckner via llvm-dev]

On Thu, Sep 7, 2017 at 11:11 AM, Robinson, Paul <paul.robinson at sony.com>
wrote:

> Different intrinsics sounds like a good solution to me. J
>
>
>
> So what happens with the case where a variable is registerized but later
> we decide to spill it?  Presumably we'd have a dbg.addr to point to the
> spill slot.  In past compilers I've used, spill slots were treated
> analogous to register allocation, i.e. some effort was made to minimize the
> number of spill slots and a variable might be spilled to different slots at
> different points.  If LLVM does that, then dbg.addr will have to be allowed
> to associated different addresses with the variable.  On the other hand, if
> LLVM allocates a unique memory "home" for each spilled variable, then
> dbg.addr can retain the property you suggest, that the address expression
> is always the same.
>

dbg.addr is really IR only. Machine DBG_VALUE instructions can already
represent addresses or values depending on their second argument. At this
point, I don't see any reason to change that.
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