[DebugInfo] Avoid crash from dropped fragments in LiveDebugValues
This patch avoids a crash caused by DW_OP_LLVM_fragments being dropped
from DIExpressions by LiveDebugValues spill-restore code. The appearance
of a previously unseen fragment configuration confuses LDV, as documented
in PR42773, and reproduced by the test function this patch adds (Crashes
on a x86_64 debug build).
To avoid this, on spill restore, we now use fragment information from the
spilt-location-expression.
In addition, when spilling, we now don't spill any DBG_VALUE with a complex
expression, as it can't be safely restored and will definitely lead to an
incorrect variable location. The discussion of this is in D65368.
Differential Revision: https://reviews.llvm.org/D66284
llvm-svn: 369026
diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp
index 3e0f51f..82231a0 100644
--- a/llvm/lib/CodeGen/LiveDebugValues.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues.cpp
@@ -691,9 +691,17 @@
"No register supplied when handling a restore of a debug value");
MachineFunction *MF = MI.getMF();
DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent());
+
+ const DIExpression *NewExpr;
+ if (auto Fragment = DebugInstr->getDebugExpression()->getFragmentInfo())
+ NewExpr = *DIExpression::createFragmentExpression(DIB.createExpression(),
+ Fragment->OffsetInBits, Fragment->SizeInBits);
+ else
+ NewExpr = DIB.createExpression();
+
NewDebugInstr =
BuildMI(*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), false,
- NewReg, DebugInstr->getDebugVariable(), DIB.createExpression());
+ NewReg, DebugInstr->getDebugVariable(), NewExpr);
VarLoc VL(*NewDebugInstr, LS);
ProcessVarLoc(VL, NewDebugInstr);
LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register restore: ";
@@ -848,9 +856,14 @@
<< "\n");
}
// Check if the register or spill location is the location of a debug value.
+ // FIXME: Don't create a spill transfer if there is a complex expression,
+ // because we currently cannot recover the original expression on restore.
for (unsigned ID : OpenRanges.getVarLocs()) {
+ const MachineInstr *DebugInstr = &VarLocIDs[ID].MI;
+
if (TKind == TransferKind::TransferSpill &&
- VarLocIDs[ID].isDescribedByReg() == Reg) {
+ VarLocIDs[ID].isDescribedByReg() == Reg &&
+ !DebugInstr->getDebugExpression()->isComplex()) {
LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
<< VarLocIDs[ID].Var.getVar()->getName() << ")\n");
} else if (TKind == TransferKind::TransferRestore &&