[DebugInfo][DAG] Process FrameIndex dbg.values unconditionally

A FrameIndex should be valid throughout a block regardless of what instructions
get selected in that block -- therefore we shouldn't harness dbg.values that
refer to FrameIndexes to an SDNode. There are numerous codegen reasons why
an SDNode never appears or doesn't become a location that a DBG_VALUE can
refer to. None of them actually affect the variable location.

Therefore, before any other tests to encode dbg_values in a SelectionDAG,
identify FrameIndex operands and encode them unattached to any SDNode.

Differential Revision: https://reviews.llvm.org/D57328

llvm-svn: 352467

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 5275dd0f6eb..d0caf3938a8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5320,6 +5320,21 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
       return nullptr;
     }
 
+    // If the Value is a frame index, we can create a FrameIndex debug value
+    // without relying on the DAG at all.
+    if (const AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
+      auto SI = FuncInfo.StaticAllocaMap.find(AI);
+      if (SI != FuncInfo.StaticAllocaMap.end()) {
+        auto SDV =
+            DAG.getFrameIndexDbgValue(Variable, Expression, SI->second,
+                                      /*IsIndirect*/ false, dl, SDNodeOrder);
+        // Do not attach the SDNodeDbgValue to an SDNode: this variable location
+        // is still available even if the SDNode gets optimized out.
+        DAG.AddDbgValue(SDV, nullptr, false);
+        return nullptr;
+      }
+    }
+
     // Do not use getValue() in here; we don't want to generate code at
     // this point if it hasn't been done yet.
     SDValue N = NodeMap[V];