Preserve debug info when DAG-combinging (zext (truncate x)) -> (and x, mask).

rdar://problem/27139077

llvm-svn: 317825

3 files changed, 46 insertions, 33 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 86c4f2c3565..557cf6d5212 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7613,7 +7613,11 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
     if (!LegalOperations || TLI.isOperationLegal(ISD::AND, VT)) {
       SDValue Op = DAG.getAnyExtOrTrunc(N0.getOperand(0), SDLoc(N), VT);
       AddToWorklist(Op.getNode());
-      return DAG.getZeroExtendInReg(Op, SDLoc(N), MinVT.getScalarType());
+      SDValue And = DAG.getZeroExtendInReg(Op, SDLoc(N), MinVT.getScalarType());
+      // We may safely transfer the debug info describing the truncate node over
+      // to the equivalent and operation.
+      DAG.transferDbgValues(N0, And);
+      return And;
     }
   }
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
index 0d85bccdeac..053d562a244 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
@@ -835,34 +835,6 @@ void DAGTypeLegalizer::GetExpandedInteger(SDValue Op, SDValue &Lo,
   Hi = Entry.second;
 }
 
-/// Transfer debug values by generating fragment expressions for split-up
-/// values.
-static void transferDbgValues(SelectionDAG &DAG, SDValue From, SDValue To,
-                              unsigned OffsetInBits) {
-  SDNode *FromNode = From.getNode();
-  SDNode *ToNode = To.getNode();
-  assert(FromNode != ToNode);
-
-  SmallVector<SDDbgValue *, 2> ClonedDVs;
-  for (SDDbgValue *Dbg : DAG.GetDbgValues(FromNode)) {
-    if (Dbg->getKind() != SDDbgValue::SDNODE)
-      break;
-
-    DIVariable *Var = Dbg->getVariable();
-    if (auto Fragment = DIExpression::createFragmentExpression(
-            Dbg->getExpression(), OffsetInBits, To.getValueSizeInBits())) {
-      SDDbgValue *Clone = DAG.getDbgValue(Var, *Fragment, ToNode, To.getResNo(),
-                                          Dbg->isIndirect(), Dbg->getDebugLoc(),
-                                          Dbg->getOrder());
-      ClonedDVs.push_back(Clone);
-    }
-    Dbg->setIsInvalidated();
-  }
-
-  for (SDDbgValue *Dbg : ClonedDVs)
-    DAG.AddDbgValue(Dbg, ToNode, false);
-}
-
 void DAGTypeLegalizer::SetExpandedInteger(SDValue Op, SDValue Lo,
                                           SDValue Hi) {
   assert(Lo.getValueType() ==
@@ -875,11 +847,13 @@ void DAGTypeLegalizer::SetExpandedInteger(SDValue Op, SDValue Lo,
 
   // Transfer debug values.
   if (DAG.getDataLayout().isBigEndian()) {
-    transferDbgValues(DAG, Op, Hi, 0);
-    transferDbgValues(DAG, Op, Lo, Hi.getValueSizeInBits());
+    DAG.transferDbgValues(Op, Hi, 0, Hi.getValueSizeInBits());
+    DAG.transferDbgValues(Op, Lo, Hi.getValueSizeInBits(),
+                          Lo.getValueSizeInBits());
   } else {
-    transferDbgValues(DAG, Op, Lo, 0);
-    transferDbgValues(DAG, Op, Hi, Lo.getValueSizeInBits());
+    DAG.transferDbgValues(Op, Lo, 0, Lo.getValueSizeInBits());
+    DAG.transferDbgValues(Op, Hi, Lo.getValueSizeInBits(),
+                          Hi.getValueSizeInBits());
   }
 
   // Remember that this is the result of the node.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 2fb2615b072..1c4589ef14f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -7026,6 +7026,41 @@ SDDbgValue *SelectionDAG::getFrameIndexDbgValue(DIVariable *Var,
   return new (DbgInfo->getAlloc()) SDDbgValue(Var, Expr, FI, DL, O);
 }
 
+void SelectionDAG::transferDbgValues(SDValue From, SDValue To,
+                                     unsigned OffsetInBits,
+                                     unsigned SizeInBits) {
+  SDNode *FromNode = From.getNode();
+  SDNode *ToNode = To.getNode();
+  assert(FromNode != ToNode);
+
+  SmallVector<SDDbgValue *, 2> ClonedDVs;
+  for (SDDbgValue *Dbg : GetDbgValues(FromNode)) {
+    if (Dbg->getKind() != SDDbgValue::SDNODE)
+      break;
+
+    DIVariable *Var = Dbg->getVariable();
+    auto *Expr = Dbg->getExpression();
+    // If a fragment is requested, update the expression.
+    if (SizeInBits) {
+      auto Fragment = DIExpression::createFragmentExpression(
+          Dbg->getExpression(), OffsetInBits, SizeInBits);
+      if (Fragment)
+        Expr = *Fragment;
+    }
+    // Clone the SbgValue unless the fragment creation failed.
+    if (!SizeInBits || (SizeInBits && Expr)) {
+      SDDbgValue *Clone =
+          getDbgValue(Var, Expr, ToNode, To.getResNo(), Dbg->isIndirect(),
+                      Dbg->getDebugLoc(), Dbg->getOrder());
+      ClonedDVs.push_back(Clone);
+    }
+    Dbg->setIsInvalidated();
+  }
+
+  for (SDDbgValue *Dbg : ClonedDVs)
+    AddDbgValue(Dbg, ToNode, false);
+}
+
 void SelectionDAG::salvageDebugInfo(SDNode &N) {
   if (!N.getHasDebugValue())
     return;