On Feb 27, 2013, at 11:42 AM, Eric Christopher <[email protected]> wrote:
> On Wed, Feb 27, 2013 at 11:39 AM, Adrian Prantl <[email protected]> wrote:
>
> On Feb 27, 2013, at 11:31 AM, John McCall <[email protected]> wrote:
> > Okay, you're saying that the value is actually no longer live at all at
> > this point in the function? It seems reasonable to lose track of the debug
> > info then, although we should be leaving behind a marker in the DWARF that
> > says the value is unavailable.
> >
> > If we want to make stronger guarantees in -O0 for purposes of debugging —
> > and I think that's reasonable — then throwing the value in an alloca is
> > acceptable.
>
> To clarify: Are you suggesting to only generate the alloca at -O0, or are you
> comfortable with it as it is?
>
> If the value isn't live past that spot I'm more comfortable with dropping the
> debug info there rather than changing the generated code to keep the value
> live through the end of the function.
Purely out of attachment to the principle that debug info shouldn't change the
code?
Not losing information has intrinsic value in a debug build. If we need to
emit slightly different code in order to force a value to stay live and thus
improve the debugging experience, then so be it.
John.
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