[DwarfExpression] Support entry values for indirect parameters

Summary:
A struct argument can be passed-by-value to a callee via a pointer to a
temporary stack copy. Add support for emitting an entry value DBG_VALUE
when an indirect parameter DBG_VALUE becomes unavailable. This is done
by omitting DW_OP_stack_value from the entry value expression, to make
the expression describe the location of an object.

rdar://63373691

Reviewers: djtodoro, aprantl, dstenb

Subscribers: hiraditya, lldb-commits, llvm-commits

Tags: #lldb, #llvm

Differential Revision: https://reviews.llvm.org/D80345

1 files changed, 1 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp
index 470cb22..00a6149a 100644
--- a/llvm/lib/CodeGen/LiveDebugValues.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues.cpp
@@ -1613,10 +1613,6 @@ bool LiveDebugValues::isEntryValueCandidate(
   if (MI.getDebugLoc()->getInlinedAt())
     return false;
 
-  // Do not consider indirect debug values (TODO: explain why).
-  if (MI.isIndirectDebugValue())
-    return false;
-
   // Only consider parameters that are described using registers. Parameters
   // that are passed on the stack are not yet supported, so ignore debug
   // values that are described by the frame or stack pointer.
@@ -1631,7 +1627,7 @@ bool LiveDebugValues::isEntryValueCandidate(
     return false;
 
   // TODO: Add support for parameters that have a pre-existing debug expressions
-  // (e.g. fragments, or indirect parameters using DW_OP_deref).
+  // (e.g. fragments).
   if (MI.getDebugExpression()->getNumElements() > 0)
     return false;