[PATCH] D37078: [DebugInfo] Handle memory locations in LiveDebugValues

[Reid Kleckner via Phabricator via llvm-commits]

rnk added inline comments.


================
Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:5173
+    // node map.
+    // FIXME: Handle byval/inalloca params as above.
+    if (const AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
----------------
aprantl wrote:
> I think this should be a separate commit?
Ugh, this doesn't actually do the right thing. Here's my test that comes here:
```
void useptr(int *);
void use_alloca(int cond) {
  int x = 0;
  int *px = &x;
  if (cond)
    useptr(px);
}
```

After optimization, `px` will be described by a dbg.value of x's alloca. This code in InstrEmitter.cpp incorrectly builds an "indirect in memory" DBG_VALUE for px:
```
  if (SD->getKind() == SDDbgValue::FRAMEIX) {
    // Stack address; this needs to be lowered in target-dependent fashion.
    // EmitTargetCodeForFrameDebugValue is responsible for allocation.
    return BuildMI(*MF, DL, TII->get(TargetOpcode::DBG_VALUE))
        .addFrameIndex(SD->getFrameIx())
        .addImm(0)
        .addMetadata(Var)
        .addMetadata(Expr);
  }
```

I guess I'll need to fix that to look for DW_OP_deref.


https://reviews.llvm.org/D37078