[PATCH] D136247: [NFC][SelectionDAG][DebugInfo] Remove duplicate parameter from handleDebugValue

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

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[NFC][SelectionDAG][DebugInfo] Remove duplicate parameter from handleDebugValue

`handleDebugValue` has two `DebugLoc` parameters that appear to always take the
same value. Remove one of the duplicate parameters.

Now an attempt to disentangle the code and explain why I think they are always
the same value:

The call to `handleDebugValue` in `visitIntrinsicCall` uses `dl` and
`DI.getDebugLoc()` as the two `DebugLoc` arguments, where `DI` is the
current instruction being visited casted to a `DbgValueInst`.

At the start of `visitIntrinsicCall` we can see

  DebugLoc dl = getCurDebugLoc();

Here's the definition for `getCurDebugLoc`:

  DebugLoc getCurDebugLoc() const {
    return CurInst ? CurInst->getDebugLoc() : DebugLoc();
  }

Noting that `CurInst` is set to the instruction-being-visited in
`SelectionDAGBuilder::visit(const Instruction &I)` before calling `visit`
which results in the call to `visitIntrinsicCall`. This shows that `dl`
and `DI.getDebugLoc()` are the same.

The other two calls to `handleDebugValue` occur inside 
`SelectionDAGBuilder::salvageUnresolvedDbgValue(DanglingDebugInfo &DDI)`. The
two `DebugLoc`s passed to `handleDebugValue` from here are:

  DebugLoc DL = DDI.getdl();
  DebugLoc InstDL = DDI.getDI()->getDebugLoc();

The `DanglingDebugInfo` parameter `DDI` is created by the call from
`visitIntrinsicCall` to `addDanglingDebugInfo`:

  addDanglingDebugInfo(&DI, dl, SDNodeOrder);

So following the logic for the arguments to the call to `handleDebugValue` in
`visitIntrinsicCall`, `DDI.getdl()` and `DDI.getDI()->getDebugLoc()` used in
`salvageUnresolvedDbgValue` are also the same value.

To help test this I added an assert to check the arguments were equal and built
the CTMark test suite - the assert wasn't tripped. That's not conclusive, but
adds confidence.

---

I'll put up another NFC patch that removes unneeded `DebugLoc` field from
`DanglingDebugInfo` shortly.

As well as being a nice tidy-up, these changes is used by an upcoming assignment tracking patch.


https://reviews.llvm.org/D136247

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h

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