[PATCH] D146543: [Coroutines] Look for dbg.declare for temp spills

[Wei Wang via Phabricator via llvm-commits]

weiwang added a comment.

In D146543#4655210 <https://reviews.llvm.org/D146543#4655210>, @fdeazeve wrote:

> I understand the problem the patch is solving, but I haven't been able to figure out how we are going from that dbg.declare that I mentioned to the one that ends up in the final output of the compiler. Do you see the problem that I was trying to point to? The _first_ dbg.declare that we create -- the one shown in the output of `p CurrentBlock->dump()`-- is not equivalent to the original dbg.declare. And yet, somehow, this "invalid" dbg.declare disappears and the correct one shows up later. To be very specific, when we do:
>
>   DIBuilder(*CurrentBlock->getParent()->getParent(), AllowUnresolved)
>                 .insertDeclare(CurrentReload, DDI->getVariable(),
>                                DDI->getExpression(), DDI->getDebugLoc(),
>                                &*Builder.GetInsertPoint());
>
> The `CurrentReload` argument seems incorrect if we stripped some of the loads along the way. Does that make sense?

I think the reason is that the reload `%this1.reload` is after a suspend point, so the `DbgDeclareInst ` (DDI) is unreachable from the ramp function and removed later. But since it is reachable in resume and destroy copies, it shows up there.

  for (DbgDeclareInst *DDI : DIs) {
    bool AllowUnresolved = false;
    // This dbg.declare is preserved for all coro-split function
    // fragments. It will be unreachable in the main function, and
    // processed by coro::salvageDebugInfo() by CoroCloner.
    DIBuilder(*CurrentBlock->getParent()->getParent(), AllowUnresolved)
        .insertDeclare(CurrentReload, DDI->getVariable(),
                       DDI->getExpression(), DDI->getDebugLoc(),
                       &*Builder.GetInsertPoint());
    // This dbg.declare is for the main function entry point.  It
    // will be deleted in all coro-split functions.
    coro::salvageDebugInfo(ArgToAllocaMap, DDI, Shape.OptimizeFrame,
                           false /*UseEntryValue*/);
  }




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