Add a way for a frontend to generate more complex dwarf location

information.  This allows arbitrary code involving DW_OP_plus_uconst
and DW_OP_deref.  The scheme allows for easy extention to include,
any, or all of the DW_OP_ opcodes.  I thought about just exposing all
of them, but, wasn't sure if people wanted the dwarf opcodes exposed
in the api.  Is that a layering violation?

With this scheme, the entire existing block scheme used by llvm-gcc
can be switched over to the new scheme.  I think that would be
cleaner, as then the compiler specific bits are not present in llvm
proper.  Before the old code can be yanked however, similar code in
clang would have to be removed.

Next up, more testing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83120 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 117 insertions, 10 deletions

diff --git a/include/llvm/Analysis/DebugInfo.h b/include/llvm/Analysis/DebugInfo.h
index 8082279..c40cfb2 100644
--- a/include/llvm/Analysis/DebugInfo.h
+++ b/include/llvm/Analysis/DebugInfo.h
@@ -187,10 +187,10 @@ namespace llvm {
   class DIType : public DIDescriptor {
   public:
     enum {
-      FlagPrivate    = 1 << 0,
-      FlagProtected  = 1 << 1,
-      FlagFwdDecl    = 1 << 2,
-      FlagAppleBlock = 1 << 3,
+      FlagPrivate          = 1 << 0,
+      FlagProtected        = 1 << 1,
+      FlagFwdDecl          = 1 << 2,
+      FlagAppleBlock       = 1 << 3,
       FlagBlockByrefStruct = 1 << 4
     };
 
@@ -409,6 +409,17 @@ namespace llvm {
     /// Verify - Verify that a variable descriptor is well formed.
     bool Verify() const;
 
+    /// HasComplexAddr - Return true if the variable has a complex address.
+    bool hasComplexAddress() const {
+      return getNumAddrElements() > 0;
+    }
+
+    unsigned getNumAddrElements() const { return DbgNode->getNumElements()-6; }
+
+    uint64_t getAddrElement(unsigned Idx) const {
+      return getUInt64Field(Idx+6);
+    }
+
     /// isBlockByrefVariable - Return true if the variable was declared as
     /// a "__block" variable (Apple Blocks).
     bool isBlockByrefVariable() const {
@@ -463,6 +474,8 @@ namespace llvm {
     DIFactory(const DIFactory &);     // DO NOT IMPLEMENT
     void operator=(const DIFactory&); // DO NOT IMPLEMENT
   public:
+    enum ComplexAddrKind { OpPlus=1, OpDeref };
+
     explicit DIFactory(Module &m);
 
     /// GetOrCreateArray - Create an descriptor for an array of descriptors.
@@ -540,6 +553,14 @@ namespace llvm {
                               DICompileUnit CompileUnit, unsigned LineNo,
                               DIType Type);
 
+    /// CreateComplexVariable - Create a new descriptor for the specified
+    /// variable which has a complex address expression for its address.
+    DIVariable CreateComplexVariable(unsigned Tag, DIDescriptor Context,
+                                     const std::string &Name,
+                                     DICompileUnit CompileUnit, unsigned LineNo,
+                                     DIType Type,
+                                     SmallVector<Value *, 9> &addr);
+
     /// CreateLexicalBlock - This creates a descriptor for a lexical block
     /// with the specified parent context.
     DILexicalBlock CreateLexicalBlock(DIDescriptor Context);
diff --git a/lib/Analysis/DebugInfo.cpp b/lib/Analysis/DebugInfo.cpp
index 58bee90..db5a0cb 100644
--- a/lib/Analysis/DebugInfo.cpp
+++ b/lib/Analysis/DebugInfo.cpp
@@ -531,6 +531,8 @@ void DIVariable::dump() const {
   errs() << " [" << getLineNumber() << "] ";
   getType().dump();
   errs() << "\n";
+
+  // FIXME: Dump complex addresses
 }
 
 //===----------------------------------------------------------------------===//
@@ -781,6 +783,26 @@ DIVariable DIFactory::CreateVariable(unsigned Tag, DIDescriptor Context,
 }
 
 
+/// CreateComplexVariable - Create a new descriptor for the specified variable
+/// which has a complex address expression for its address.
+DIVariable DIFactory::CreateComplexVariable(unsigned Tag, DIDescriptor Context,
+                                            const std::string &Name,
+                                            DICompileUnit CompileUnit,
+                                            unsigned LineNo,
+                                   DIType Type, SmallVector<Value *, 9> &addr) {
+  SmallVector<Value *, 9> Elts;
+  Elts.push_back(GetTagConstant(Tag));
+  Elts.push_back(Context.getNode());
+  Elts.push_back(MDString::get(VMContext, Name));
+  Elts.push_back(CompileUnit.getNode());
+  Elts.push_back(ConstantInt::get(Type::getInt32Ty(VMContext), LineNo));
+  Elts.push_back(Type.getNode());
+  Elts.insert(Elts.end(), addr.begin(), addr.end());
+
+  return DIVariable(MDNode::get(VMContext, &Elts[0], 6+addr.size()));
+}
+
+
 /// CreateBlock - This creates a descriptor for a lexical block with the
 /// specified parent VMContext.
 DILexicalBlock DIFactory::CreateLexicalBlock(DIDescriptor Context) {
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index f667e31..8a74a8e 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -556,7 +556,7 @@ DIType DwarfDebug::GetBlockByrefType(DIType Ty, std::string Name) {
   unsigned tag = Ty.getTag();
 
   if (tag == dwarf::DW_TAG_pointer_type) {
-    DIDerivedType DTy = DIDerivedType (Ty.getNode());
+    DIDerivedType DTy = DIDerivedType(Ty.getNode());
     subType = DTy.getTypeDerivedFrom();
   }
 
@@ -577,6 +577,56 @@ DIType DwarfDebug::GetBlockByrefType(DIType Ty, std::string Name) {
   return Ty;
 }
 
+/// AddComplexAddress - Start with the address based on the location provided,
+/// and generate the DWARF information necessary to find the actual variable
+/// given the extra address information encoded in the DIVariable, starting from
+/// the starting location.  Add the DWARF information to the die.
+///
+void DwarfDebug::AddComplexAddress(DbgVariable *&DV, DIE *Die,
+                                   unsigned Attribute,
+                                   const MachineLocation &Location) {
+  const DIVariable &VD = DV->getVariable();
+  DIType Ty = VD.getType();
+
+  // Decode the original location, and use that as the start of the byref
+  // variable's location.
+  unsigned Reg = RI->getDwarfRegNum(Location.getReg(), false);
+  DIEBlock *Block = new DIEBlock();
+
+  if (Location.isReg()) {
+    if (Reg < 32) {
+      AddUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_reg0 + Reg);
+    } else {
+      Reg = Reg - dwarf::DW_OP_reg0;
+      AddUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_breg0 + Reg);
+      AddUInt(Block, 0, dwarf::DW_FORM_udata, Reg);
+    }
+  } else {
+    if (Reg < 32)
+      AddUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_breg0 + Reg);
+    else {
+      AddUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_bregx);
+      AddUInt(Block, 0, dwarf::DW_FORM_udata, Reg);
+    }
+
+    AddUInt(Block, 0, dwarf::DW_FORM_sdata, Location.getOffset());
+  }
+
+  for (unsigned i = 0, N = VD.getNumAddrElements(); i < N; ++i) {
+    uint64_t Element = VD.getAddrElement(i);
+
+    if (Element == DIFactory::OpPlus) {
+      AddUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_plus_uconst);
+      AddUInt(Block, 0, dwarf::DW_FORM_udata, VD.getAddrElement(++i));
+    } else if (Element == DIFactory::OpDeref) {
+      AddUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_deref);
+    } else llvm_unreachable("unknown DIFactory Opcode");
+  }
+
+  // Now attach the location information to the DIE.
+  AddBlock(Die, Attribute, 0, Block);
+}
+
 /* Byref variables, in Blocks, are declared by the programmer as "SomeType
    VarName;", but the compiler creates a __Block_byref_x_VarName struct, and
    gives the variable VarName either the struct, or a pointer to the struct, as
@@ -649,7 +699,7 @@ void DwarfDebug::AddBlockByrefAddress(DbgVariable *&DV, DIE *Die,
   const char *varName = VD.getName();
 
   if (Tag == dwarf::DW_TAG_pointer_type) {
-    DIDerivedType DTy = DIDerivedType (Ty.getNode());
+    DIDerivedType DTy = DIDerivedType(Ty.getNode());
     TmpTy = DTy.getTypeDerivedFrom();
     isPointer = true;
   }
@@ -790,7 +840,6 @@ void DwarfDebug::AddType(CompileUnit *DW_Unit, DIE *Entity, DIType Ty) {
   else {
     assert(Ty.isDerivedType() && "Unknown kind of DIType");
     ConstructTypeDIE(DW_Unit, Buffer, DIDerivedType(Ty.getNode()));
-
   }
 
   // Add debug information entry to entity and appropriate context.
@@ -1187,6 +1236,7 @@ DIE *DwarfDebug::CreateDbgScopeVariable(DbgVariable *DV, CompileUnit *Unit) {
   AddSourceLine(VariableDie, &VD);
 
   // Add variable type.
+  // FIXME: isBlockByrefVariable should be reformulated in terms of complex addresses instead.
   if (VD.isBlockByrefVariable())
     AddType(Unit, VariableDie, GetBlockByrefType(VD.getType(), Name));
   else
@@ -1200,7 +1250,10 @@ DIE *DwarfDebug::CreateDbgScopeVariable(DbgVariable *DV, CompileUnit *Unit) {
     Location.set(RI->getFrameRegister(*MF),
                  RI->getFrameIndexOffset(*MF, DV->getFrameIndex()));
 
-    if (VD.isBlockByrefVariable())
+
+    if (VD.hasComplexAddress())
+      AddComplexAddress(DV, VariableDie, dwarf::DW_AT_location, Location);
+    else if (VD.isBlockByrefVariable())
       AddBlockByrefAddress(DV, VariableDie, dwarf::DW_AT_location, Location);
     else
       AddAddress(VariableDie, dwarf::DW_AT_location, Location);
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index f582f9b..8899529 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -284,10 +284,20 @@ class VISIBILITY_HIDDEN DwarfDebug : public Dwarf {
   void AddAddress(DIE *Die, unsigned Attribute,
                   const MachineLocation &Location);
 
+  /// AddComplexAddress - Start with the address based on the location provided,
+  /// and generate the DWARF information necessary to find the actual variable
+  /// (navigating the extra location information encoded in the type) based on
+  /// the starting location.  Add the DWARF information to the die.
+  ///
+  void AddComplexAddress(DbgVariable *&DV, DIE *Die, unsigned Attribute,
+                         const MachineLocation &Location);
+
+  // FIXME: Should be reformulated in terms of AddComplexAddress.
   /// AddBlockByrefAddress - Start with the address based on the location
   /// provided, and generate the DWARF information necessary to find the
   /// actual Block variable (navigating the Block struct) based on the
-  /// starting location.  Add the DWARF information to the die.
+  /// starting location.  Add the DWARF information to the die.  Obsolete,
+  /// please use AddComplexAddress instead.
   ///
   void AddBlockByrefAddress(DbgVariable *&DV, DIE *Die, unsigned Attribute,
                             const MachineLocation &Location);
@@ -459,8 +469,9 @@ class VISIBILITY_HIDDEN DwarfDebug : public Dwarf {
 
   void ConstructSubprogram(MDNode *N);
 
+  // FIXME: This should go away in favor of complex addresses.
   /// Find the type the programmer originally declared the variable to be
-  /// and return that type.
+  /// and return that type.  Obsolete, use GetComplexAddrType instead.
   ///
   DIType GetBlockByrefType(DIType Ty, std::string Name);