Use DW_OP_stack_value when reconstructing variable values with arithmetic.
When the location description of a source variable involves arithmetic
on the value itself, it needs to be marked with DW_OP_stack_value since it
is not describing the variable's location, but rather its value.
This is a follow-up to r297971 and fixes the source testcase quoted in
the comment in debuginfo-dce.ll.
rdar://problem/30725338
This reapplies r301093 without modifications.
llvm-svn: 301210
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 09924d1..357c303 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1268,21 +1268,37 @@
}
}
-/// Prepend \p DIExpr with a deref and offset operation.
+enum { WithStackValue = true };
+
+/// Prepend \p DIExpr with a deref and offset operation and optionally turn it
+/// into a stack value.
static DIExpression *prependDIExpr(DIBuilder &Builder, DIExpression *DIExpr,
- bool Deref, int64_t Offset) {
- if (!Deref && !Offset)
+ bool Deref, int64_t Offset = 0,
+ bool StackValue = false) {
+ if (!Deref && !Offset && !StackValue)
return DIExpr;
- // Create a copy of the original DIDescriptor for user variable, prepending
- // "deref" operation to a list of address elements, as new llvm.dbg.declare
- // will take a value storing address of the memory for variable, not
- // alloca itself.
- SmallVector<uint64_t, 4> Ops;
+
+ SmallVector<uint64_t, 8> Ops;
+ appendOffset(Ops, Offset);
if (Deref)
Ops.push_back(dwarf::DW_OP_deref);
- appendOffset(Ops, Offset);
if (DIExpr)
- Ops.append(DIExpr->elements_begin(), DIExpr->elements_end());
+ for (auto Op : DIExpr->expr_ops()) {
+ // A DW_OP_stack_value comes at the end, but before a DW_OP_LLVM_fragment.
+ if (StackValue) {
+ if (Op.getOp() == dwarf::DW_OP_stack_value)
+ StackValue = false;
+ else if (Op.getOp() == dwarf::DW_OP_LLVM_fragment) {
+ Ops.push_back(dwarf::DW_OP_stack_value);
+ StackValue = false;
+ }
+ }
+ Ops.push_back(Op.getOp());
+ for (unsigned I = 0; I < Op.getNumArgs(); ++I)
+ Ops.push_back(Op.getArg(I));
+ }
+ if (StackValue)
+ Ops.push_back(dwarf::DW_OP_stack_value);
return Builder.createExpression(Ops);
}
@@ -1374,12 +1390,15 @@
unsigned BitWidth =
M.getDataLayout().getPointerSizeInBits(GEP->getPointerAddressSpace());
APInt Offset(BitWidth, 0);
- // Rewrite a constant GEP into a DIExpression.
+ // Rewrite a constant GEP into a DIExpression. Since we are performing
+ // arithmetic to compute the variable's *value* in the DIExpression, we
+ // need to mark the expression with a DW_OP_stack_value.
if (GEP->accumulateConstantOffset(M.getDataLayout(), Offset)) {
auto *DIExpr = DVI->getExpression();
DIBuilder DIB(M, /*AllowUnresolved*/ false);
// GEP offsets are i32 and thus always fit into an int64_t.
- DIExpr = prependDIExpr(DIB, DIExpr, NoDeref, Offset.getSExtValue());
+ DIExpr = prependDIExpr(DIB, DIExpr, NoDeref, Offset.getSExtValue(),
+ WithStackValue);
DVI->setOperand(0, MDWrap(I.getOperand(0)));
DVI->setOperand(3, MetadataAsValue::get(I.getContext(), DIExpr));
DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');
@@ -1391,7 +1410,7 @@
// Rewrite the load into DW_OP_deref.
auto *DIExpr = DVI->getExpression();
DIBuilder DIB(M, /*AllowUnresolved*/ false);
- DIExpr = prependDIExpr(DIB, DIExpr, WithDeref, 0);
+ DIExpr = prependDIExpr(DIB, DIExpr, WithDeref);
DVI->setOperand(0, MDWrap(I.getOperand(0)));
DVI->setOperand(3, MetadataAsValue::get(I.getContext(), DIExpr));
DEBUG(dbgs() << "SALVAGE: " << *DVI << '\n');