[LLVM][IR] Resolve Verifier FIXME: remove if (V->isArtificial()) check

[gAlfonso-bit]

Summary

The FIXME is no longer relevant, so let's remove it.

[gAlfonso-bit]

This undos commit ba6ec4b70bc49bf8b65b59f64b43df4df3fe786e, which was done in 2015, and a temporary measure. This behavior from clang has changed since then, especially when dealing with GDB.

[jeroen.dobbelaere]

Do you have an idea what changes in clang make this obsolete ?

[gAlfonso-bit]

I do not have commit access. Could someone please land this for me?

[xgupta]

In D110475#3023642, @jeroen.dobbelaere wrote:

Do you have an idea what changes in clang make this obsolete ?

@gAlfonso-bit can you address this comment before the patch gets committed?

[gAlfonso-bit]

Yes, the big one being that we don't use GDB and use LLDB instead. @xgupta

[gAlfonso-bit]

@xgupta any updates?

[gAlfonso-bit]

@aprantl any updates?

[jeroen.dobbelaere]

In D110475#3127752, @gAlfonso-bit wrote:

Yes, the big one being that we don't use GDB and use LLDB instead. @xgupta

I was more interested in knowing what change in clang related to producing artificial debug info (isArtificial) makes this valid now. If there was no such change, then the assertions in verifyFragmentExpression might trigger (Or this code should not have been there).

llvm/lib/IR/Verifier.cpp

void Verifier::verifyFragmentExpression(const DbgVariableIntrinsic &I) {
   if (!V || !E || !E->isValid())
     return;
 
   // Nothing to do if this isn't a DW_OP_LLVM_fragment expression.
   auto Fragment = E->getFragmentInfo();
   if (!Fragment)
     return;
 
-  // The frontend helps out GDB by emitting the members of local anonymous
-  // unions as artificial local variables with shared storage. When SROA splits
-  // the storage for artificial local variables that are smaller than the entire
-  // union, the overhang piece will be outside of the allotted space for the
-  // variable and this check fails.
-  // FIXME: Remove this check as soon as clang stops doing this; it hides bugs.
-  if (V->isArtificial())
-    return;
-
   verifyFragmentExpression(*V, *Fragment, &I);
 }
 
 template <typename ValueOrMetadata>
 void Verifier::verifyFragmentExpression(const DIVariable &V,
                                         DIExpression::FragmentInfo Fragment,
                                         ValueOrMetadata *Desc) {
   // If there's no size, the type is broken, but that should be checked