Debug info for optimized code: Support variables that are on the stack and

described by DBG_VALUEs during their lifetime.

Previously, when a variable was at a FrameIndex for any part of its
lifetime, this would shadow all other DBG_VALUEs and only a single
fbreg location would be emitted, which in fact is only valid for a small
range and not the entire lexical scope of the variable. The included
dbg-value-const-byref testcase demonstrates this.

This patch fixes this by
Local
- emitting dbg.value intrinsics for allocas that are passed by reference
- dropping all dbg.declares (they are now fully lowered to dbg.values)
SelectionDAG
- renamed constructors for SDDbgValue for better readability.
- fix UserValue::match() to handle indirect values correctly
- not inserting an MMI table entries for dbg.values that describe allocas.
- lowering dbg.values that describe allocas into *indirect* DBG_VALUEs.
CodeGenPrepare
- leaving dbg.values for an alloca were they are (see comment)
Other
- regenerated/updated instcombine-intrinsics testcase and included source


rdar://problem/16679879
http://reviews.llvm.org/D3374

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207130 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 43 insertions, 25 deletions

diff --git a/lib/CodeGen/SelectionDAG/InstrEmitter.cpp b/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
index c134454e0d..7c124b8caa 100644
--- a/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
+++ b/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
@@ -688,10 +688,13 @@ InstrEmitter::EmitDbgValue(SDDbgValue *SD,
     MIB.addReg(0U);
   }
 
-  if (Offset != 0) // Indirect addressing.
+  // Indirect addressing is indicated by an Imm as the second parameter.
+  if (SD->isIndirect())
     MIB.addImm(Offset);
-  else
+  else {
+    assert(Offset == 0 && "direct value cannot have an offset");
     MIB.addReg(0U, RegState::Debug);
+  }
 
   MIB.addMetadata(MDPtr);
 
diff --git a/lib/CodeGen/SelectionDAG/SDNodeDbgValue.h b/lib/CodeGen/SelectionDAG/SDNodeDbgValue.h
index b62bd623c4..ee54292831 100644
--- a/lib/CodeGen/SelectionDAG/SDNodeDbgValue.h
+++ b/lib/CodeGen/SelectionDAG/SDNodeDbgValue.h
@@ -45,14 +45,17 @@ private:
     unsigned FrameIx;       // valid for stack objects
   } u;
   MDNode *mdPtr;
+  bool IsIndirect;
   uint64_t Offset;
   DebugLoc DL;
   unsigned Order;
   bool Invalid;
 public:
   // Constructor for non-constants.
-  SDDbgValue(MDNode *mdP, SDNode *N, unsigned R, uint64_t off, DebugLoc dl,
-             unsigned O) : mdPtr(mdP), Offset(off), DL(dl), Order(O),
+  SDDbgValue(MDNode *mdP, SDNode *N, unsigned R,
+	     bool indir, uint64_t off, DebugLoc dl,
+             unsigned O) : mdPtr(mdP), IsIndirect(indir),
+			   Offset(off), DL(dl), Order(O),
                            Invalid(false) {
     kind = SDNODE;
     u.s.Node = N;
@@ -62,14 +65,16 @@ public:
   // Constructor for constants.
   SDDbgValue(MDNode *mdP, const Value *C, uint64_t off, DebugLoc dl,
              unsigned O) : 
-    mdPtr(mdP), Offset(off), DL(dl), Order(O), Invalid(false) {
+    mdPtr(mdP), IsIndirect(false), Offset(off), DL(dl), Order(O),
+    Invalid(false) {
     kind = CONST;
     u.Const = C;
   }
 
   // Constructor for frame indices.
   SDDbgValue(MDNode *mdP, unsigned FI, uint64_t off, DebugLoc dl, unsigned O) : 
-    mdPtr(mdP), Offset(off), DL(dl), Order(O), Invalid(false) {
+    mdPtr(mdP), IsIndirect(false), Offset(off), DL(dl), Order(O),
+    Invalid(false) {
     kind = FRAMEIX;
     u.FrameIx = FI;
   }
@@ -92,6 +97,9 @@ public:
   // Returns the FrameIx for a stack object
   unsigned getFrameIx() { assert (kind==FRAMEIX); return u.FrameIx; }
 
+  // Returns whether this is an indirect value.
+  bool isIndirect() { return IsIndirect; }
+
   // Returns the offset.
   uint64_t getOffset() { return Offset; }
 
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index f3974461da..6ebedfc67a 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5646,21 +5646,26 @@ SDNode *SelectionDAG::getNodeIfExists(unsigned Opcode, SDVTList VTList,
 
 /// getDbgValue - Creates a SDDbgValue node.
 ///
+/// SDNode
 SDDbgValue *
-SelectionDAG::getDbgValue(MDNode *MDPtr, SDNode *N, unsigned R, uint64_t Off,
+SelectionDAG::getDbgValue(MDNode *MDPtr, SDNode *N, unsigned R,
+			  bool IsIndirect, uint64_t Off,
                           DebugLoc DL, unsigned O) {
-  return new (Allocator) SDDbgValue(MDPtr, N, R, Off, DL, O);
+  return new (Allocator) SDDbgValue(MDPtr, N, R, IsIndirect, Off, DL, O);
 }
 
+/// Constant
 SDDbgValue *
-SelectionDAG::getDbgValue(MDNode *MDPtr, const Value *C, uint64_t Off,
-                          DebugLoc DL, unsigned O) {
+SelectionDAG::getConstantDbgValue(MDNode *MDPtr, const Value *C,
+				  uint64_t Off,
+				  DebugLoc DL, unsigned O) {
   return new (Allocator) SDDbgValue(MDPtr, C, Off, DL, O);
 }
 
+/// FrameIndex
 SDDbgValue *
-SelectionDAG::getDbgValue(MDNode *MDPtr, unsigned FI, uint64_t Off,
-                          DebugLoc DL, unsigned O) {
+SelectionDAG::getFrameIndexDbgValue(MDNode *MDPtr, unsigned FI, uint64_t Off,
+				    DebugLoc DL, unsigned O) {
   return new (Allocator) SDDbgValue(MDPtr, FI, Off, DL, O);
 }
 
@@ -6066,6 +6071,7 @@ void SelectionDAG::TransferDbgValues(SDValue From, SDValue To) {
     SDDbgValue *Dbg = *I;
     if (Dbg->getKind() == SDDbgValue::SDNODE) {
       SDDbgValue *Clone = getDbgValue(Dbg->getMDPtr(), ToNode, To.getResNo(),
+				      Dbg->isIndirect(),
                                       Dbg->getOffset(), Dbg->getDebugLoc(),
                                       Dbg->getOrder());
       ClonedDVs.push_back(Clone);
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index f20d07a4c7..3b95640392 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -992,11 +992,14 @@ void SelectionDAGBuilder::resolveDanglingDebugInfo(const Value *V,
     unsigned DbgSDNodeOrder = DDI.getSDNodeOrder();
     MDNode *Variable = DI->getVariable();
     uint64_t Offset = DI->getOffset();
+    // FIXME: This does not handle indirect values at offset 0.
+    bool IsIndirect = (Offset != 0);
     SDDbgValue *SDV;
     if (Val.getNode()) {
       if (!EmitFuncArgumentDbgValue(V, Variable, Offset, Val)) {
         SDV = DAG.getDbgValue(Variable, Val.getNode(),
-                              Val.getResNo(), Offset, dl, DbgSDNodeOrder);
+                              Val.getResNo(), IsIndirect,
+			      Offset, dl, DbgSDNodeOrder);
         DAG.AddDbgValue(SDV, Val.getNode(), false);
       }
     } else
@@ -4744,8 +4747,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
         FrameIndexSDNode *FINode = dyn_cast<FrameIndexSDNode>(N.getNode());
         if (FINode)
           // Byval parameter.  We have a frame index at this point.
-          SDV = DAG.getDbgValue(Variable, FINode->getIndex(),
-                                0, dl, SDNodeOrder);
+          SDV = DAG.getFrameIndexDbgValue(Variable, FINode->getIndex(),
+					  0, dl, SDNodeOrder);
         else {
           // Address is an argument, so try to emit its dbg value using
           // virtual register info from the FuncInfo.ValueMap.
@@ -4754,7 +4757,7 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
         }
       } else if (AI)
         SDV = DAG.getDbgValue(Variable, N.getNode(), N.getResNo(),
-                              0, dl, SDNodeOrder);
+                              true, 0, dl, SDNodeOrder);
       else {
         // Can't do anything with other non-AI cases yet.
         DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
@@ -4774,8 +4777,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
             DenseMap<const AllocaInst*, int>::iterator SI =
               FuncInfo.StaticAllocaMap.find(AI);
             if (SI != FuncInfo.StaticAllocaMap.end()) {
-              SDV = DAG.getDbgValue(Variable, SI->second,
-                                    0, dl, SDNodeOrder);
+              SDV = DAG.getFrameIndexDbgValue(Variable, SI->second,
+                                              0, dl, SDNodeOrder);
               DAG.AddDbgValue(SDV, nullptr, false);
               return nullptr;
             }
@@ -4802,7 +4805,7 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
 
     SDDbgValue *SDV;
     if (isa<ConstantInt>(V) || isa<ConstantFP>(V) || isa<UndefValue>(V)) {
-      SDV = DAG.getDbgValue(Variable, V, Offset, dl, SDNodeOrder);
+      SDV = DAG.getConstantDbgValue(Variable, V, Offset, dl, SDNodeOrder);
       DAG.AddDbgValue(SDV, nullptr, false);
     } else {
       // Do not use getValue() in here; we don't want to generate code at
@@ -4813,8 +4816,11 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
         N = UnusedArgNodeMap[V];
       if (N.getNode()) {
         if (!EmitFuncArgumentDbgValue(V, Variable, Offset, N)) {
+	  // A dbg.value for an alloca is always indirect.
+	  bool IsIndirect(isa<AllocaInst>(V));
           SDV = DAG.getDbgValue(Variable, N.getNode(),
-                                N.getResNo(), Offset, dl, SDNodeOrder);
+                                N.getResNo(), IsIndirect,
+				Offset, dl, SDNodeOrder);
           DAG.AddDbgValue(SDV, N.getNode(), false);
         }
       } else if (!V->use_empty() ) {
@@ -4843,11 +4849,6 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
       FuncInfo.StaticAllocaMap.find(AI);
     if (SI == FuncInfo.StaticAllocaMap.end())
       return nullptr; // VLAs.
-    int FI = SI->second;
-
-    MachineModuleInfo &MMI = DAG.getMachineFunction().getMMI();
-    if (!DI.getDebugLoc().isUnknown() && MMI.hasDebugInfo())
-      MMI.setVariableDbgInfo(Variable, FI, DI.getDebugLoc());
     return nullptr;
   }