bridge/go-llvm-dibuildhelper.cpp - gollvm - Git at Google

 //===-- go-llvm-dibuildhelper.cpp - implementation of DIBuildHelper -------===//
 //
 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 //
 //===----------------------------------------------------------------------===//
 //
 // Methods for DIBuildHelper class.
 //
 //===----------------------------------------------------------------------===//

 #include "go-llvm-dibuildhelper.h"
 #include "go-llvm-typemanager.h"
 #include "go-llvm-bexpression.h"
 #include "go-llvm-bstatement.h"
 #include "go-llvm-bfunction.h"
 #include "go-llvm-bvariable.h"

 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/FileSystem.h"

 DIBuildHelper::DIBuildHelper(llvm::Module *module,
                              TypeManager *typemanager,
                              Llvm_linemap *linemap)
     : module_(module), typemanager_(typemanager), linemap_(linemap), moduleScope_(nullptr),
       dibuilder_(new llvm::DIBuilder(*module)), topblock_(nullptr),
       entryBlock_(nullptr), known_locations_(0)
 {
 }

 void DIBuildHelper::createCompileUnitIfNeeded()
 {
   if (moduleScope_)
     return;

   // Create compile unit
   llvm::SmallString<256> currentDir;
   llvm::sys::fs::current_path(currentDir);
   std::string filestr = applyDebugPrefix(linemap_->get_initial_file());
   auto primaryFile = dibuilder_->createFile(filestr, currentDir);
   bool isOptimized = true;
   std::string compileFlags; // FIXME
   unsigned runtimeVersion = 0; // not sure what would be for Go
   moduleScope_ =
       dibuilder_->createCompileUnit(llvm::dwarf::DW_LANG_Go, primaryFile,
                                     "llvm-goc", isOptimized,
                                     compileFlags, runtimeVersion);
   pushDIScope(moduleScope_);

   module_->addModuleFlag(llvm::Module::Warning, "Debug Info Version",
                          llvm::DEBUG_METADATA_VERSION);
   module_->addModuleFlag(llvm::Module::Warning, "Dwarf Version", 4);
 }

 void DIBuildHelper::finalize()
 {
   createCompileUnitIfNeeded();

   // Emit any globals we've collected along the way.
   for (auto it : globalsToProcess_) {
     Bvariable *v = it.first;
     bool isExported = it.second;
     llvm::DIFile *vfile = diFileFromLocation(v->location());
     unsigned vline = linemap()->location_line(v->location());
     llvm::DIType *vdit = typemanager()->buildDIType(v->btype(), *this);
     bool isLocalToUnit = !isExported;
     dibuilder().createGlobalVariableExpression(moduleScope_,
                                                v->name(), v->name(),
                                                vfile, vline, vdit,
                                                isLocalToUnit);
   }

   dibuilder_->finalize();
 }


 void DIBuildHelper::processGlobal(Bvariable *v, bool isExported)
 {
   globalsToProcess_.push_back(std::make_pair(v, isExported));
 }

 void DIBuildHelper::beginFunction(Bfunction *function,
                                   Bnode *topnode,
                                   llvm::BasicBlock *entryBlock)
 {
   createCompileUnitIfNeeded();

   assert(entryBlock_ == nullptr);
   assert(entryBlock != nullptr);
   entryBlock_ = entryBlock;

   assert(topblock_ == nullptr);
   assert(topnode->castToBblock());
   topblock_ = topnode->castToBblock();

   known_locations_ = 0;

   // Create proper DIType for function
   llvm::DIType *dit =
       typemanager()->buildDIType(function->fcnType(), *this);
   llvm::DISubroutineType *dst =
       llvm::cast<llvm::DISubroutineType>(dit);

   // Now the function entry itself
   unsigned fcnLine = linemap()->location_line(function->location());
   bool isLocalToUnit = !function->function()->hasExternalLinkage();
   unsigned scopeLine = fcnLine; // FIXME -- determine correct value here
   llvm::DIFile *difile = diFileFromLocation(function->location());
   llvm::DINode::DIFlags flags = llvm::DINode::FlagZero;
   llvm::DISubprogram::DISPFlags spflags = llvm::DISubprogram::SPFlagDefinition;
   if (isLocalToUnit)
     spflags |= llvm::DISubprogram::SPFlagLocalToUnit;
   auto difunc =
       dibuilder().createFunction(moduleScope(), function->name(),
                                  isLocalToUnit ? "" : function->asmName(),
                                  difile, fcnLine, dst, scopeLine, flags,
                                  spflags);
   pushDIScope(difunc);
 }

 void DIBuildHelper::processVarsInBLock(const std::vector<Bvariable*> &vars,
                                        llvm::DIScope *scope)
 {
   for (auto &v : vars) {
     if (v->isTemporary())
       continue;
     if (declared_.find(v) != declared_.end())
       continue;
     declared_.insert(v);

     llvm::DIFile *vfile = diFileFromLocation(v->location());
     llvm::DIType *vdit =
         typemanager()->buildDIType(v->btype(), *this);
     unsigned vline = linemap()->location_line(v->location());
     llvm::DILocalVariable *dilv =
         dibuilder().createAutoVariable(scope, v->name(), vfile, vline, vdit);
     insertVarDecl(v, dilv);
   }
 }

 void DIBuildHelper::insertVarDecl(Bvariable *var,
                                   llvm::DILocalVariable *dilv)
 {
   llvm::DIExpression *expr = dibuilder().createExpression();
   llvm::DILocation *vloc = debugLocFromLocation(var->location());

   // Don't emit declaration for dead variable.
   if(var->initializer() && !var->initializerInstruction()->getParent())
     return;

   // Create the declare instruction, giving it an initial position at
   // the end of the entry block (the insertDeclare call below doesn't
   // allow a NULL insert location, so we pick end-of-block arbitrarily).
   assert(entryBlock_);
   llvm::Instruction *decl =
       dibuilder().insertDeclare(var->value(), dilv, expr, vloc, entryBlock_);
   decl->removeFromParent();

   // Extract the decl from the end of the entry block and reposition
   // it according to the var properties.
   llvm::Instruction *insertionPoint = nullptr;
   if (var->initializer()) {
     assert(var->initializerInstruction()->getParent());
     insertionPoint = var->initializerInstruction();
   } else if (var->flavor() == ParamVar) {
     // parameters passing by reference may have no initializers.
     // declare them at function entry.
     entryBlock_->getInstList().push_front(decl);
     return;
   } else {
     // locals with no initializer should only be zero-sized vars.
     // make them available immediately after their alloca.
     assert(typemanager()->typeSize(var->btype()) == 0);
     llvm::Instruction *alloca = llvm::cast<llvm::Instruction>(var->value());
     insertionPoint = alloca;
   }

   assert(! llvm::isa<llvm::BranchInst>(insertionPoint));
   assert(insertionPoint != insertionPoint->getParent()->getTerminator());
   decl->insertAfter(insertionPoint);
 }

 void DIBuildHelper::endFunction(Bfunction *function)
 {
   cleanFileScope();
   llvm::DISubprogram *fscope = llvm::cast<llvm::DISubprogram>(currentDIScope());

   // Create debug meta-data for parameter variables.
   unsigned argIdx = 0;
   for (auto &v : function->getParameterVars()) {
     llvm::DIFile *vfile = diFileFromLocation(v->location());
     llvm::DIType *vdit =
         typemanager()->buildDIType(v->btype(), *this);
     unsigned vline = linemap()->location_line(v->location());
     llvm::DILocalVariable *dilv =
         dibuilder().createParameterVariable(fscope, v->name(), ++argIdx,
                                             vfile, vline, vdit);
     insertVarDecl(v, dilv);
   }

   // Create debug meta-data for local variables. We wait to do this
   // here so as to insure that the initializer instructions for the
   // variables have been assigned to a basic block. Note that
   // block-scoped locals (as opposed to function-scoped locals) will
   // already have been processed at this point.
   processVarsInBLock(function->getFunctionLocalVars(), fscope);

   // If a given function has no debug locations at all, then don't
   // try to mark it as having debug info (without doing this we can
   // wind up having functions flagged as problematic by the verifier).
   if (known_locations_)
     function->function()->setSubprogram(fscope);

   // Done with this scope
   cleanFileScope();
   popDIScope();
   assert(diScopeStack_.size() == 1);

   // Clean up
   entryBlock_ = nullptr;
   topblock_ = nullptr;
   known_locations_ = 0;
   declared_.clear();
 }

 // Front end tends to declare more blocks than strictly required for
 // debug generation purposes, so here we examine each block to see
 // whether it makes sense to generate a DWARF lexical scope record for
 // it. In particular, we look for blocks containing no user-visible
 // variables (these can be omitted).
 //
 // Return TRUE if this is an interesting block (needs DWARF scope) or
 // FALSE otherwise.

 bool DIBuildHelper::interestingBlock(Bblock *block)
 {
   assert(block);
   bool foundInteresting = false;
   for (auto &v : block->vars()) {
     if (! v->isTemporary()) {
       foundInteresting = true;
       break;
     }
   }
   return foundInteresting;
 }

 void DIBuildHelper::beginLexicalBlock(Bblock *block)
 {
   if (! interestingBlock(block) || block == topblock_)
     return;

   // Register block with DIBuilder
   Location bloc = block->location();
   llvm::DIFile *file = diFileFromLocation(block->location());
   llvm::DILexicalBlock *dilb =
       dibuilder().createLexicalBlock(currentDIScope(), file,
                                      linemap()->location_line(bloc),
                                      linemap()->location_column(bloc));
   pushDIScope(dilb);
 }

 void DIBuildHelper::endLexicalBlock(Bblock *block)
 {
   if (! interestingBlock(block))
     return;

   cleanFileScope();

   // In the case of the top block, we still want to process any local
   // variables it contains, but we'll want to insure that they are
   // parented by the function itself.
   //
   llvm::DIScope *scope =
       (block == topblock_ ? currentDIScope() : popDIScope());

   processVarsInBLock(block->vars(), scope);
 }

 void DIBuildHelper::processExprInst(Bstatement *stmt,
                                     Bexpression *expr,
                                     llvm::Instruction *inst)
 {
   Location loc = expr->location();
   if (linemap()->is_unknown(loc)) {
     Location sloc = stmt->location();
     if (!linemap()->is_unknown(sloc))
       loc = sloc;
   }
   if (! linemap()->is_unknown(loc)) {
     known_locations_ += 1;
     inst->setDebugLoc(debugLocFromLocation(loc));
   }
 }

 void DIBuildHelper::addDebugPrefix(std::pair<llvm::StringRef, llvm::StringRef> pref)
 {
   std::string from(pref.first);
   std::string to(pref.second);
   debugPrefixMap_[from] = to;
 }

 std::string DIBuildHelper::applyDebugPrefix(llvm::StringRef path) {
   for (const auto &remap : debugPrefixMap_)
     if (path.startswith(remap.first))
       return (llvm::Twine(remap.second) +
               path.substr(remap.first.size())).str();
   return path.str();
 }

 llvm::DIFile *DIBuildHelper::diFileFromLocation(Location location)
 {
   std::string locfile = applyDebugPrefix(linemap()->location_file(location));
   llvm::StringRef locdir = llvm::sys::path::parent_path(locfile);
   llvm::StringRef locfilename = llvm::sys::path::filename(locfile);
   if (linemap()->is_predeclared(location))
     locdir = "";
   return dibuilder().createFile(locfilename, locdir);
 }

 llvm::DebugLoc DIBuildHelper::debugLocFromLocation(Location loc)
 {
   llvm::LLVMContext &context = typemanager()->context();

   // In the (somewhat unusual) case of a file/line directive, create a new
   // pseudo-scope to capture the fact that the file has changed. Pop off
   // any previously created file scope prior to doing this.
   llvm::DIFile *curFile = currentDIScope()->getFile();
   llvm::DIFile *locFile = diFileFromLocation(loc);
   if (curFile != locFile) {
     cleanFileScope();
     llvm::DILexicalBlockFile *dilbf =
         dibuilder().createLexicalBlockFile(currentDIScope(), locFile);
     pushDIScope(dilbf);
   }

   return llvm::DILocation::get(context, linemap()->location_line(loc),
                                linemap()->location_column(loc),
                                currentDIScope());
 }

 llvm::DIScope *DIBuildHelper::currentDIScope()
 {
   assert(diScopeStack_.size());
   return diScopeStack_.back();
 }

 llvm::DIScope *DIBuildHelper::popDIScope()
 {
   assert(diScopeStack_.size());
   llvm::DIScope *popped = diScopeStack_.back();
   diScopeStack_.pop_back();
   return popped;
 }

 void DIBuildHelper::pushDIScope(llvm::DIScope *scope)
 {
   assert(scope);
   diScopeStack_.push_back(scope);
 }

 void DIBuildHelper::cleanFileScope()
 {
   assert(diScopeStack_.size());
   if (llvm::dyn_cast<llvm::DILexicalBlockFile>(diScopeStack_.back()) != nullptr)
     diScopeStack_.pop_back();
 }
	//===-- go-llvm-dibuildhelper.cpp - implementation of DIBuildHelper -------===//
	//
	// Copyright 2018 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.
	//
	//===----------------------------------------------------------------------===//
	//
	// Methods for DIBuildHelper class.
	//
	//===----------------------------------------------------------------------===//

	#include "go-llvm-dibuildhelper.h"
	#include "go-llvm-typemanager.h"
	#include "go-llvm-bexpression.h"
	#include "go-llvm-bstatement.h"
	#include "go-llvm-bfunction.h"
	#include "go-llvm-bvariable.h"

	#include "llvm/IR/DIBuilder.h"
	#include "llvm/IR/DebugInfo.h"
	#include "llvm/IR/DebugInfoMetadata.h"
	#include "llvm/IR/DebugLoc.h"
	#include "llvm/IR/Function.h"
	#include "llvm/IR/Instructions.h"
	#include "llvm/IR/Module.h"
	#include "llvm/Support/FileSystem.h"

	DIBuildHelper::DIBuildHelper(llvm::Module *module,
	TypeManager *typemanager,
	Llvm_linemap *linemap)
	: module_(module), typemanager_(typemanager), linemap_(linemap), moduleScope_(nullptr),
	dibuilder_(new llvm::DIBuilder(*module)), topblock_(nullptr),
	entryBlock_(nullptr), known_locations_(0)
	{
	}

	void DIBuildHelper::createCompileUnitIfNeeded()
	{
	if (moduleScope_)
	return;

	// Create compile unit
	llvm::SmallString<256> currentDir;
	llvm::sys::fs::current_path(currentDir);
	std::string filestr = applyDebugPrefix(linemap_->get_initial_file());
	auto primaryFile = dibuilder_->createFile(filestr, currentDir);
	bool isOptimized = true;
	std::string compileFlags; // FIXME
	unsigned runtimeVersion = 0; // not sure what would be for Go
	moduleScope_ =
	dibuilder_->createCompileUnit(llvm::dwarf::DW_LANG_Go, primaryFile,
	"llvm-goc", isOptimized,
	compileFlags, runtimeVersion);
	pushDIScope(moduleScope_);

	module_->addModuleFlag(llvm::Module::Warning, "Debug Info Version",
	llvm::DEBUG_METADATA_VERSION);
	module_->addModuleFlag(llvm::Module::Warning, "Dwarf Version", 4);
	}

	void DIBuildHelper::finalize()
	{
	createCompileUnitIfNeeded();

	// Emit any globals we've collected along the way.
	for (auto it : globalsToProcess_) {
	Bvariable *v = it.first;
	bool isExported = it.second;
	llvm::DIFile *vfile = diFileFromLocation(v->location());
	unsigned vline = linemap()->location_line(v->location());
	llvm::DIType vdit = typemanager()->buildDIType(v->btype(), this);
	bool isLocalToUnit = !isExported;
	dibuilder().createGlobalVariableExpression(moduleScope_,
	v->name(), v->name(),
	vfile, vline, vdit,
	isLocalToUnit);
	}

	dibuilder_->finalize();
	}



	void DIBuildHelper::processGlobal(Bvariable *v, bool isExported)
	{
	globalsToProcess_.push_back(std::make_pair(v, isExported));
	}

	void DIBuildHelper::beginFunction(Bfunction *function,
	Bnode *topnode,
	llvm::BasicBlock *entryBlock)
	{
	createCompileUnitIfNeeded();

	assert(entryBlock_ == nullptr);
	assert(entryBlock != nullptr);
	entryBlock_ = entryBlock;

	assert(topblock_ == nullptr);
	assert(topnode->castToBblock());
	topblock_ = topnode->castToBblock();

	known_locations_ = 0;

	// Create proper DIType for function
	llvm::DIType *dit =
	typemanager()->buildDIType(function->fcnType(), *this);
	llvm::DISubroutineType *dst =
	llvm::cast<llvm::DISubroutineType>(dit);

	// Now the function entry itself
	unsigned fcnLine = linemap()->location_line(function->location());
	bool isLocalToUnit = !function->function()->hasExternalLinkage();
	unsigned scopeLine = fcnLine; // FIXME -- determine correct value here
	llvm::DIFile *difile = diFileFromLocation(function->location());
	llvm::DINode::DIFlags flags = llvm::DINode::FlagZero;
	llvm::DISubprogram::DISPFlags spflags = llvm::DISubprogram::SPFlagDefinition;
	if (isLocalToUnit)
	spflags \|= llvm::DISubprogram::SPFlagLocalToUnit;
	auto difunc =
	dibuilder().createFunction(moduleScope(), function->name(),
	isLocalToUnit ? "" : function->asmName(),
	difile, fcnLine, dst, scopeLine, flags,
	spflags);
	pushDIScope(difunc);
	}

	void DIBuildHelper::processVarsInBLock(const std::vector<Bvariable*> &vars,
	llvm::DIScope *scope)
	{
	for (auto &v : vars) {
	if (v->isTemporary())
	continue;
	if (declared_.find(v) != declared_.end())
	continue;
	declared_.insert(v);

	llvm::DIFile *vfile = diFileFromLocation(v->location());
	llvm::DIType *vdit =
	typemanager()->buildDIType(v->btype(), *this);
	unsigned vline = linemap()->location_line(v->location());
	llvm::DILocalVariable *dilv =
	dibuilder().createAutoVariable(scope, v->name(), vfile, vline, vdit);
	insertVarDecl(v, dilv);
	}
	}

	void DIBuildHelper::insertVarDecl(Bvariable *var,
	llvm::DILocalVariable *dilv)
	{
	llvm::DIExpression *expr = dibuilder().createExpression();
	llvm::DILocation *vloc = debugLocFromLocation(var->location());

	// Don't emit declaration for dead variable.
	if(var->initializer() && !var->initializerInstruction()->getParent())
	return;

	// Create the declare instruction, giving it an initial position at
	// the end of the entry block (the insertDeclare call below doesn't
	// allow a NULL insert location, so we pick end-of-block arbitrarily).
	assert(entryBlock_);
	llvm::Instruction *decl =
	dibuilder().insertDeclare(var->value(), dilv, expr, vloc, entryBlock_);
	decl->removeFromParent();

	// Extract the decl from the end of the entry block and reposition
	// it according to the var properties.
	llvm::Instruction *insertionPoint = nullptr;
	if (var->initializer()) {
	assert(var->initializerInstruction()->getParent());
	insertionPoint = var->initializerInstruction();
	} else if (var->flavor() == ParamVar) {
	// parameters passing by reference may have no initializers.
	// declare them at function entry.
	entryBlock_->getInstList().push_front(decl);
	return;
	} else {
	// locals with no initializer should only be zero-sized vars.
	// make them available immediately after their alloca.
	assert(typemanager()->typeSize(var->btype()) == 0);
	llvm::Instruction *alloca = llvm::cast<llvm::Instruction>(var->value());
	insertionPoint = alloca;
	}

	assert(! llvm::isa<llvm::BranchInst>(insertionPoint));
	assert(insertionPoint != insertionPoint->getParent()->getTerminator());
	decl->insertAfter(insertionPoint);
	}

	void DIBuildHelper::endFunction(Bfunction *function)
	{
	cleanFileScope();
	llvm::DISubprogram *fscope = llvm::cast<llvm::DISubprogram>(currentDIScope());

	// Create debug meta-data for parameter variables.
	unsigned argIdx = 0;
	for (auto &v : function->getParameterVars()) {
	llvm::DIFile *vfile = diFileFromLocation(v->location());
	llvm::DIType *vdit =
	typemanager()->buildDIType(v->btype(), *this);
	unsigned vline = linemap()->location_line(v->location());
	llvm::DILocalVariable *dilv =
	dibuilder().createParameterVariable(fscope, v->name(), ++argIdx,
	vfile, vline, vdit);
	insertVarDecl(v, dilv);
	}

	// Create debug meta-data for local variables. We wait to do this
	// here so as to insure that the initializer instructions for the
	// variables have been assigned to a basic block. Note that
	// block-scoped locals (as opposed to function-scoped locals) will
	// already have been processed at this point.
	processVarsInBLock(function->getFunctionLocalVars(), fscope);

	// If a given function has no debug locations at all, then don't
	// try to mark it as having debug info (without doing this we can
	// wind up having functions flagged as problematic by the verifier).
	if (known_locations_)
	function->function()->setSubprogram(fscope);

	// Done with this scope
	cleanFileScope();
	popDIScope();
	assert(diScopeStack_.size() == 1);

	// Clean up
	entryBlock_ = nullptr;
	topblock_ = nullptr;
	known_locations_ = 0;
	declared_.clear();
	}

	// Front end tends to declare more blocks than strictly required for
	// debug generation purposes, so here we examine each block to see
	// whether it makes sense to generate a DWARF lexical scope record for
	// it. In particular, we look for blocks containing no user-visible
	// variables (these can be omitted).
	//
	// Return TRUE if this is an interesting block (needs DWARF scope) or
	// FALSE otherwise.

	bool DIBuildHelper::interestingBlock(Bblock *block)
	{
	assert(block);
	bool foundInteresting = false;
	for (auto &v : block->vars()) {
	if (! v->isTemporary()) {
	foundInteresting = true;
	break;
	}
	}
	return foundInteresting;
	}

	void DIBuildHelper::beginLexicalBlock(Bblock *block)
	{
	if (! interestingBlock(block) \|\| block == topblock_)
	return;

	// Register block with DIBuilder
	Location bloc = block->location();
	llvm::DIFile *file = diFileFromLocation(block->location());
	llvm::DILexicalBlock *dilb =
	dibuilder().createLexicalBlock(currentDIScope(), file,
	linemap()->location_line(bloc),
	linemap()->location_column(bloc));
	pushDIScope(dilb);
	}

	void DIBuildHelper::endLexicalBlock(Bblock *block)
	{
	if (! interestingBlock(block))
	return;

	cleanFileScope();

	// In the case of the top block, we still want to process any local
	// variables it contains, but we'll want to insure that they are
	// parented by the function itself.
	//
	llvm::DIScope *scope =
	(block == topblock_ ? currentDIScope() : popDIScope());

	processVarsInBLock(block->vars(), scope);
	}

	void DIBuildHelper::processExprInst(Bstatement *stmt,
	Bexpression *expr,
	llvm::Instruction *inst)
	{
	Location loc = expr->location();
	if (linemap()->is_unknown(loc)) {
	Location sloc = stmt->location();
	if (!linemap()->is_unknown(sloc))
	loc = sloc;
	}
	if (! linemap()->is_unknown(loc)) {
	known_locations_ += 1;
	inst->setDebugLoc(debugLocFromLocation(loc));
	}
	}

	void DIBuildHelper::addDebugPrefix(std::pair<llvm::StringRef, llvm::StringRef> pref)
	{
	std::string from(pref.first);
	std::string to(pref.second);
	debugPrefixMap_[from] = to;
	}

	std::string DIBuildHelper::applyDebugPrefix(llvm::StringRef path) {
	for (const auto &remap : debugPrefixMap_)
	if (path.startswith(remap.first))
	return (llvm::Twine(remap.second) +
	path.substr(remap.first.size())).str();
	return path.str();
	}

	llvm::DIFile *DIBuildHelper::diFileFromLocation(Location location)
	{
	std::string locfile = applyDebugPrefix(linemap()->location_file(location));
	llvm::StringRef locdir = llvm::sys::path::parent_path(locfile);
	llvm::StringRef locfilename = llvm::sys::path::filename(locfile);
	if (linemap()->is_predeclared(location))
	locdir = "";
	return dibuilder().createFile(locfilename, locdir);
	}

	llvm::DebugLoc DIBuildHelper::debugLocFromLocation(Location loc)
	{
	llvm::LLVMContext &context = typemanager()->context();

	// In the (somewhat unusual) case of a file/line directive, create a new
	// pseudo-scope to capture the fact that the file has changed. Pop off
	// any previously created file scope prior to doing this.
	llvm::DIFile *curFile = currentDIScope()->getFile();
	llvm::DIFile *locFile = diFileFromLocation(loc);
	if (curFile != locFile) {
	cleanFileScope();
	llvm::DILexicalBlockFile *dilbf =
	dibuilder().createLexicalBlockFile(currentDIScope(), locFile);
	pushDIScope(dilbf);
	}

	return llvm::DILocation::get(context, linemap()->location_line(loc),
	linemap()->location_column(loc),
	currentDIScope());
	}

	llvm::DIScope *DIBuildHelper::currentDIScope()
	{
	assert(diScopeStack_.size());
	return diScopeStack_.back();
	}

	llvm::DIScope *DIBuildHelper::popDIScope()
	{
	assert(diScopeStack_.size());
	llvm::DIScope *popped = diScopeStack_.back();
	diScopeStack_.pop_back();
	return popped;
	}

	void DIBuildHelper::pushDIScope(llvm::DIScope *scope)
	{
	assert(scope);
	diScopeStack_.push_back(scope);
	}

	void DIBuildHelper::cleanFileScope()
	{
	assert(diScopeStack_.size());
	if (llvm::dyn_cast<llvm::DILexicalBlockFile>(diScopeStack_.back()) != nullptr)
	diScopeStack_.pop_back();
	}