fdeazeve added a comment.
The code in Mem2Reg (Local.cpp) is wrong in the presence of DIExprs, but by
luck we conservatively don't do anything.
The function below is roughly doing: "if this store covers the entire size of
the `DIVar`, rewrite the dbg declare into a dbg value.
This is only correct if the `DIExpr` is empty. In most cases, "luckily" the
size of a pointer doesn't match the size of the `DIVar`, but it should be
possible to come up with IR examples where we generate invalid debug
information in the presence of a `OP_deref`.
/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
/// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic.
void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
StoreInst *SI, DIBuilder &Builder)
{
assert(DII->isAddressOfVariable() || isa<DbgAssignIntrinsic>(DII));
auto *DIVar = DII->getVariable();
assert(DIVar && "Missing variable");
auto *DIExpr = DII->getExpression();
DIExpr->startsWithDeref();
Value *DV = SI->getValueOperand();
DebugLoc NewLoc = getDebugValueLoc(DII);
if (!valueCoversEntireFragment(DV->getType(), DII)) {
// FIXME: If storing to a part of the variable described by the
dbg.declare,
// then we want to insert a dbg.value for the corresponding fragment.
LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
<< *DII << '\n');
// For now, when there is a store to parts of the variable (but we do not
// know which part) we insert an dbg.value intrinsic to indicate that we
// know nothing about the variable's content.
DV = UndefValue::get(DV->getType());
Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
return;
}
Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
}
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D141381/new/
https://reviews.llvm.org/D141381
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