SymbolRewriter.cpp | Explore in Territory

//===- SymbolRewriter.cpp - Symbol Rewriter -------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// SymbolRewriter is a LLVM pass which can rewrite symbols transparently within
// existing code.  It is implemented as a compiler pass and is configured via a
// YAML configuration file.
//
// The YAML configuration file format is as follows:
//
// RewriteMapFile := RewriteDescriptors
// RewriteDescriptors := RewriteDescriptor | RewriteDescriptors
// RewriteDescriptor := RewriteDescriptorType ':' '{' RewriteDescriptorFields '}'
// RewriteDescriptorFields := RewriteDescriptorField | RewriteDescriptorFields
// RewriteDescriptorField := FieldIdentifier ':' FieldValue ','
// RewriteDescriptorType := Identifier
// FieldIdentifier := Identifier
// FieldValue := Identifier
// Identifier := [0-9a-zA-Z]+
//
// Currently, the following descriptor types are supported:
//
// - function:          (function rewriting)
//      + Source        (original name of the function)
//      + Target        (explicit transformation)
//      + Transform     (pattern transformation)
//      + Naked         (boolean, whether the function is undecorated)
// - global variable:   (external linkage global variable rewriting)
//      + Source        (original name of externally visible variable)
//      + Target        (explicit transformation)
//      + Transform     (pattern transformation)
// - global alias:      (global alias rewriting)
//      + Source        (original name of the aliased name)
//      + Target        (explicit transformation)
//      + Transform     (pattern transformation)
//
// Note that source and exactly one of [Target, Transform] must be provided
//
// New rewrite descriptors can be created.  Addding a new rewrite descriptor
// involves:
//
//  a) extended the rewrite descriptor kind enumeration
//     (<anonymous>::RewriteDescriptor::RewriteDescriptorType)
//  b) implementing the new descriptor
//     (c.f. <anonymous>::ExplicitRewriteFunctionDescriptor)
//  c) extending the rewrite map parser
//     (<anonymous>::RewriteMapParser::parseEntry)
//
//  Specify to rewrite the symbols using the `-rewrite-symbols` option, and
//  specify the map file to use for the rewriting via the `-rewrite-map-file`
//  option.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/Utils/SymbolRewriter.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/ilist.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/IR/Comdat.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalObject.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Regex.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/YAMLParser.h"
#include <memory>
#include <string>
#include <vector>

usingnamespacellvm;
usingnamespaceSymbolRewriter;

#define DEBUG_TYPE …

static cl::list<std::string> RewriteMapFiles("rewrite-map-file",
                                             cl::desc("Symbol Rewrite Map"),
                                             cl::value_desc("filename"),
                                             cl::Hidden);

static void rewriteComdat(Module &M, GlobalObject *GO,
                          const std::string &Source,
                          const std::string &Target) { … }

namespace {

template <RewriteDescriptor::Type DT, typename ValueType,
          ValueType *(Module::*Get)(StringRef) const>
class ExplicitRewriteDescriptor : public RewriteDescriptor { … };

} // end anonymous namespace

template <RewriteDescriptor::Type DT, typename ValueType,
          ValueType *(Module::*Get)(StringRef) const>
bool ExplicitRewriteDescriptor<DT, ValueType, Get>::performOnModule(Module &M) { … }

namespace {

template <RewriteDescriptor::Type DT, typename ValueType,
          ValueType *(Module::*Get)(StringRef) const,
          iterator_range<typename iplist<ValueType>::iterator>
          (Module::*Iterator)()>
class PatternRewriteDescriptor : public RewriteDescriptor { … };

} // end anonymous namespace

template <RewriteDescriptor::Type DT, typename ValueType,
          ValueType *(Module::*Get)(StringRef) const,
          iterator_range<typename iplist<ValueType>::iterator>
          (Module::*Iterator)()>
bool PatternRewriteDescriptor<DT, ValueType, Get, Iterator>::
performOnModule(Module &M) { … }

namespace {

/// Represents a rewrite for an explicitly named (function) symbol.  Both the
/// source function name and target function name of the transformation are
/// explicitly spelt out.
ExplicitRewriteFunctionDescriptor;

/// Represents a rewrite for an explicitly named (global variable) symbol.  Both
/// the source variable name and target variable name are spelt out.  This
/// applies only to module level variables.
ExplicitRewriteGlobalVariableDescriptor;

/// Represents a rewrite for an explicitly named global alias.  Both the source
/// and target name are explicitly spelt out.
ExplicitRewriteNamedAliasDescriptor;

/// Represents a rewrite for a regular expression based pattern for functions.
/// A pattern for the function name is provided and a transformation for that
/// pattern to determine the target function name create the rewrite rule.
PatternRewriteFunctionDescriptor;

/// Represents a rewrite for a global variable based upon a matching pattern.
/// Each global variable matching the provided pattern will be transformed as
/// described in the transformation pattern for the target.  Applies only to
/// module level variables.
PatternRewriteGlobalVariableDescriptor;

/// PatternRewriteNamedAliasDescriptor - represents a rewrite for global
/// aliases which match a given pattern.  The provided transformation will be
/// applied to each of the matching names.
PatternRewriteNamedAliasDescriptor;

} // end anonymous namespace

bool RewriteMapParser::parse(const std::string &MapFile,
                             RewriteDescriptorList *DL) { … }

bool RewriteMapParser::parse(std::unique_ptr<MemoryBuffer> &MapFile,
                             RewriteDescriptorList *DL) { … }

bool RewriteMapParser::parseEntry(yaml::Stream &YS, yaml::KeyValueNode &Entry,
                                  RewriteDescriptorList *DL) { … }

bool RewriteMapParser::
parseRewriteFunctionDescriptor(yaml::Stream &YS, yaml::ScalarNode *K,
                               yaml::MappingNode *Descriptor,
                               RewriteDescriptorList *DL) { … }

bool RewriteMapParser::
parseRewriteGlobalVariableDescriptor(yaml::Stream &YS, yaml::ScalarNode *K,
                                     yaml::MappingNode *Descriptor,
                                     RewriteDescriptorList *DL) { … }

bool RewriteMapParser::
parseRewriteGlobalAliasDescriptor(yaml::Stream &YS, yaml::ScalarNode *K,
                                  yaml::MappingNode *Descriptor,
                                  RewriteDescriptorList *DL) { … }

PreservedAnalyses RewriteSymbolPass::run(Module &M, ModuleAnalysisManager &AM) { … }

bool RewriteSymbolPass::runImpl(Module &M) { … }

void RewriteSymbolPass::loadAndParseMapFiles() { … }
llvm/llvm/lib/Transforms/Utils/SymbolRewriter.cpp
