Add code to handle llvm.dbg.values in SROA.

This patch adds a bunch of functions that will be used to properly
handle debug information for llvm.dbg.values in the SROA pass.

Author: rastogishubham

llvm/include/llvm/IR/DebugInfo.h

@@ -43,6 +43,8 @@ class Module;
 TinyPtrVector<DbgDeclareInst *> findDbgDeclares(Value *V);
 /// As above, for DVRDeclares.
 TinyPtrVector<DbgVariableRecord *> findDVRDeclares(Value *V);
+/// As above, for DVRValues.
+TinyPtrVector<DbgVariableRecord *> findDVRValues(Value *V);
 
 /// Finds the llvm.dbg.value intrinsics describing a value.
 void findDbgValues(

llvm/include/llvm/IR/DebugProgramInstruction.h

@@ -426,6 +426,11 @@ class DbgVariableRecord : public DbgRecord, protected DebugValueUser {
   /// Does this describe the address of a local variable. True for dbg.addr
   /// and dbg.declare, but not dbg.value, which describes its value.
   bool isAddressOfVariable() const { return Type == LocationType::Declare; }
+
+  /// Does this describe the value of a local variable. False for dbg.addr
+  /// and dbg.declare, but not True dbg.value, which describes its value.
+  bool isValueOfVariable() const { return Type == LocationType::Value; }
+
   LocationType getType() const { return Type; }
 
   void setKillLocation();

llvm/include/llvm/IR/IntrinsicInst.h

@@ -341,6 +341,13 @@ class DbgVariableIntrinsic : public DbgInfoIntrinsic {
     return getIntrinsicID() == Intrinsic::dbg_declare;
   }
 
+  /// Does this describe the value of a local variable. True for dbg.value,
+  /// but not dbg.declare, which describes its address, or dbg.assign, which
+  /// describes a combination of the variable's value and address.
+  bool isValueOfVariable() const {
+    return getIntrinsicID() == Intrinsic::dbg_value;
+  }
+
   void setKillLocation() {
     // TODO: When/if we remove duplicate values from DIArgLists, we don't need
     // this set anymore.

llvm/include/llvm/Transforms/Utils/Local.h

@@ -259,6 +259,13 @@ CallInst *changeToCall(InvokeInst *II, DomTreeUpdater *DTU = nullptr);
 ///  Dbg Intrinsic utilities
 ///
 
+/// Moves an llvm.dbg.value intrinsic before a store to an alloca'd value
+/// that has an associated llvm.dbg.value intrinsic.
+void MoveDebugValueToStoreLoc(DbgVariableRecord *DVR, StoreInst *SI,
+                              DIBuilder &Builder);
+void MoveDebugValueToStoreLoc(DbgVariableIntrinsic *DII, StoreInst *SI,
+                              DIBuilder &Builder);
+
 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
 /// that has an associated llvm.dbg.declare intrinsic.
 void ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,

llvm/lib/IR/DebugInfo.cpp

@@ -80,6 +80,23 @@ TinyPtrVector<DbgVariableRecord *> llvm::findDVRDeclares(Value *V) {
   return Declares;
 }
 
+TinyPtrVector<DbgVariableRecord *> llvm::findDVRValues(Value *V) {
+  // This function is hot. Check whether the value has any metadata to avoid a
+  // DenseMap lookup.
+  if (!V->isUsedByMetadata())
+    return {};
+  auto *L = LocalAsMetadata::getIfExists(V);
+  if (!L)
+    return {};
+
+  TinyPtrVector<DbgVariableRecord *> Values;
+  for (DbgVariableRecord *DVR : L->getAllDbgVariableRecordUsers())
+    if (DVR->getType() == DbgVariableRecord::LocationType::Value)
+      Values.push_back(DVR);
+
+  return Values;
+}
+
 template <typename IntrinsicT, bool DbgAssignAndValuesOnly>
 static void
 findDbgIntrinsics(SmallVectorImpl<IntrinsicT *> &Result, Value *V,

llvm/lib/Transforms/Utils/Local.cpp

@@ -1731,6 +1731,21 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
                                     SI->getIterator());
 }
 
+/// Moves an llvm.dbg.value intrinsic before a store to an alloca'd value
+/// that has an associated llvm.dbg.value intrinsic.
+void llvm::MoveDebugValueToStoreLoc(DbgVariableIntrinsic *DII, StoreInst *SI,
+                                    DIBuilder &Builder) {
+  auto *DIVar = DII->getVariable();
+  assert(DIVar && "Missing variable");
+  auto *DIExpr = DII->getExpression();
+  Value *DV = SI->getValueOperand();
+
+  DebugLoc NewLoc = getDebugValueLoc(DII);
+
+  insertDbgValueOrDbgVariableRecord(Builder, DV, DIVar, DIExpr, NewLoc,
+                                    SI->getIterator());
+}
+
 /// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
 /// that has an associated llvm.dbg.declare intrinsic.
 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
@@ -1805,6 +1820,19 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgVariableRecord *DVR,
   SI->getParent()->insertDbgRecordBefore(NewDVR, SI->getIterator());
 }
 
+void llvm::MoveDebugValueToStoreLoc(DbgVariableRecord *DVR, StoreInst *SI,
+                                    DIBuilder &Builder) {
+  auto *DIVar = DVR->getVariable();
+  assert(DIVar && "Missing variable");
+  auto *DIExpr = DVR->getExpression();
+  Value *DV = SI->getValueOperand();
+
+  DebugLoc NewLoc = getDebugValueLoc(DVR);
+
+  insertDbgValueOrDbgVariableRecord(Builder, DV, DIVar, DIExpr, NewLoc,
+                                    SI->getIterator());
+}
+
 /// Inserts a llvm.dbg.value intrinsic after a phi that has an associated
 /// llvm.dbg.declare intrinsic.
 void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,